GOODYEAR HYND Attention-deficit disorder with (ADD;H) and without (ADD;WO) hyperactivity; Behavioral and neuropsychological differentiation

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Journal of Clinical Child Psychology
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Attention-Deficit Disorder With (ADD/H) and
Without (ADD/WO) Hyperactivity: Behavioral and
Neuropsychological Differentiation
Patricia Goodyear & George W. Hynd
Published online: 07 Jun 2010.
To cite this article: Patricia Goodyear & George W. Hynd (1992) Attention-Deficit Disorder With (ADD/H) and Without (ADD/
WO) Hyperactivity: Behavioral and Neuropsychological Differentiation, Journal of Clinical Child Psychology, 21:3, 273-305,
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Journal olF Clinical Child Psychology 
1992, Vol. 21, No. 3, 273-305 
Copyright 1992 by 
Lawrence Erlhaum Associates, Inc. 
rlttention-Deficit Disorder With (ADD/H) and Without (AIC)D/WO) 
Hyperactivity: Behavioral and Neuropsychological Diffprentiation 
Patricia Goodyear 
Departments of Education and Psychology, Furman University 
George W. Hynd 
Departments of Special Education and Psychology, U~rsiversity of Georgia and 
Neurology, Medical College of Georgia 
Reviewed behavioral and neuropsychological studies addressing attentiop-dejicit 
disorder with (ADD/H) and without (ADD/WO) hyperactivity. Revie$ sf the 
behavioral studies suggests that children with ADD/H have more behavi?r prob- 
lems, are less popular, are more self-destructive, and are more likely t4 have a 
codiagnosis of conduct disorder. Children with ADD/ WO seem more socia fly with- 
drawn, have a slower cognitive tempo, are more self-conscious, ana! have p higher 
incidence of developmental learning disorders. Neuropsychological stwdieq suggest 
that children with ADD/H or ADD/ WO may dztfer electrophysio1o~:ically f nd that 
ADD/WO children may have defcits in autonzaticity similar to childten with 
learning disabilities. The literature provides more support for the diagnosti nonzen- 
cloture found in the Diagnostic and Statistical Manual of Mental Disor1ers (3rd 
ed.; DSM-III; American Psychiatric Association, 1980) than for the pblythetic 
approach characterizing the diagnosis of attention-defcit hyperactivity flisonder 
(ADHD) in the Diagnostic and Statistical Manual of Mental Disolrd~?rs Urd ed., 
rev.; DSM-III-R; American Psychiatric Association, 1987). 
Aniong the most common behavior disorders of 
children and adolescents are problems related to hy- 
peractivity and inattention. The American Psychiat- 
ric Association (1987) in the Diagnostic and Statisti- 
cal Manual of Mental Disorders (3rd ed., rev.; 
DSM--III--R) estimated that the disorders may 
occur in as many as 3% of children. Barkley (1982), 
after an extensive review of the literature, estimated 
prevallence at 3% to 5% of school-age children and 
suggested that these problems comprise 30% to 
40% of the total referrals to chid guidance clinics. 
Based on these estimates, then, it would be expected 
that at least one child in every classroom could be 
so identified. 
Diagnostic Nomenclature 
In the earlier second edition of the manual 
(DSM-II; American Psychiatric Association, 
1968), the disorder was known as hyperkinetic reac- 
tion qf childhood. Diagnostic emphasis was on the 
high activity level with little emphasis on symptoms 
Requests for reprints should be sent to George W. Hynd, 
Center Tor Clinical and Developmental Neuropsychology, EXC- 
Aderhold Hall, University of Georgia, Athens, GA 30602. 
of inattention. The pulblicatihn of the third edition 
(DSA4-III;. Americain ~s+hiarfric Association, 
1980) resulted in a controvers/al change in the classi- 
fication which renamed, red+finecl, and subdivided 
the previous category. 'The tedm attention defcit dis- 
order (ADD) was introduce/d to replace hyperki- 
netic reaction of childhood dnd signified a shift in 
diagnostic emphasis from a dibturbance of activity to 
a disturbance of attention (qarlson, 1986 Douglas 
& Peters, 1979; Lahey, ~cldau~lhenc~, Strauss, & 
Frame, 1984). The suk~divisiqn of the category into 
attention deficits with (ADI)/H:) and without hy- 
peractivity (ADDlWO) fu ther highlighted this 
change of emphasis as it b a a e polssible to diagnose 
level. 
F 
impairment of attentioin withgut heightened activity 
I 
Following the introducti'bn of ADD/WO in 
1980, the subtyping of atten ion deficits was criti- I 
cized as empirically unfoundqd @.:couth, 1986). Such 
criticism led to the removal of ADD/WO from 
DSM-III-R in 1987. This latest diagnostic and 
classification system has subqtitutced two disorders, 
attention-deficit hyperactivity +liiso~~iier (ADHD) and 
undzrerentiated attention-defScit d,iorder OJADD), 
for the previous ADD categoiy. According to New- 
Corn et al. (1989), almost two thirds of the ADHD 
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symptoms enumerated in DSM-III-R describe 
behaviors reflective of hyperactivity, impulsivity, or 
both; inattentive behaviors are referred to specifi- 
cally in only approximately one third of the symp- 
toms. 
The current ADHD category shifts diagnostic 
emphasis away from attention disturbance. At the 
same time, the UADD category maintains that there 
may be "disturbances in which the predominant fea- 
ture is the persistence of developmentally inappro- 
priate and marked inattention that is not a symptom 
of another disorder" (American Psychiatric Associ- 
ation, 1987, p. 95). Thus, DSM-III-R has removed 
the ADD/WO terminology but has retained the 
concept that an attention disorder may occur in the 
absence of hyperactivity. 
Although the concept of an attention disorder in 
the absence of hyperactivity has been retained, its 
diagnosis has been altered. A D D N O and UADD 
are not equivalent categories (Lahey, Schaughency, 
Hynd, Carlson, & Nieves, 1987). A D D N O diagno- 
sis (DSM-III) requires both inattention and impul- 
sivity whereas UADD (DSM-III-R) requires only 
inattention without further delineation of diagnostic 
criteria. 
Further complicating the diagnosis of attention 
disorders is the "polythetic" (Cantwell & Baker, 
1988; Lahey et al., 1987) approqch to diagnosisof 
ADHD (Hynd, Lorys, et al., 1991; Lahey et al., 
1988; Lahey et al., 1987). This polythetic approach 
requires the presence of at least 8 of 14 possible 
symptoms associated with ADHD's "essential fea- 
tures" (i.e., inattention, impulsiveness, hyperac- 
tivity; American Psychiatric Association, 1987). 
With this approach, the diagnosis of ADHD may be 
made without the requirement that. symptoms from 
each of the essential features be prfisent, an apparent 
acknowledgment of the difficulty of separating hy- 
peractivity and impulsivity characteristics (Lahey et 
al., 1988; Newcosn et al., 1984). The effect of this, 
however, is that any combination of symptoms of 
inattention and/or irnpulsivenesg and/or hyperac- 
tivity can result in an APHD diagnosis. As Ostrom 
and Jenson (1988) pointed out, "While the narrative 
description of ADHD in DSM-In-R highlights 
attentional problems, it wopld be theoretically possi- 
ble to make the diagnosis without considering any of 
the attention items" (p. 263), Table 1 summarizes 
the diagnostic, erite?ria found in DSM-111 and 
DSM- III- R. 
As predicted, Meworn et al. (1989) identified a 
group of nonreferred students meeti~g ADHD crite- 
ria who displayed hyperactive and impulsive but not 
necessarily inattentive behaviors. Based on this 
finding, the authors ooncluded that ADHD criteria 
allow identification of a more heterogeneous group 
than A D D m ariteria. August and Garfinkel (1989) 
also found heterogeneity with the ADHD criteria. 
With a nonreferred sample, they identified two inat- 
tentive-hyperactive groups; 80% exhibited behav- 
ioral difficulties and 20% exhibited cognitive diffi- 
culties such as reading disabilities. 
Both the failure to delineate UADD criteria and 
the polythetic nature of the ADHD classification 
affect the diagnosis of attention deficits in the ab- 
sence of hyperactivity. It is now likely that because 
of the combined presence of inattention and impul- 
sivity required in ADD/WO diagnosis (American 
Pychiatric Association, 1980) many A D D N O 
children will be subsumed under the ADHD poly- 
thetic criteria (Lahey et al., 1988; Lahey et al., 
1987). In fact, in a recent study, Barkley, DuPaul, 
and McMurray (1990) found that 31% of their 
ADDJWO group also met ADHD criteria. Having 
diagnostic criteria that yield such heterogeneous 
groups (using the DSM-III-R) creates further 
confusion regarding the possible presence of ADD 
subtypes and may be unwarranted because the 
change in nomenclature occurred at a time when 
empirical evidence was accumulating in support of 
behavioral differences between ADD/H and 
ADDlWO children (Brown, 1986; Cantwell, 1984; 
Cantwell & Baker, 1988; Carlson, Lahey, & 
Neeper, 1986; Dykman, Ackerman, & McCray, 
1980; Edalbro~k~ Costellp, & Kessler, 1984; King 
& Young, 1982; Lqhey, Schaughency, Frame, & 
Strauss, 1985; Lahey et al., 1987; Lahey et al., 
1984). Continued concern over the ADD subty- 
ping issue is raected in the call of the American 
Psychiatric Asslociation (1987) for researcb into the 
validity and appropriate Qa#ifi$ition of the poorly de- 
lineated UADQ aategory. This concern is intensi- 
fied by the fact that the fourth edition of the man- 
ual (DSM-I;C") is sqon ta be published, 
In this cantext then, the purpose of thie article is 
to evaluate critioally thaliterature regarding the be- 
havioral diSferer~$iation of ADD subtypes as delin- 
eated ia DSM-111 in 198B The importance of this 
issue is undoncr~rqd by recent research thslt has sug- 
gested empiriaid links, bqtwem children with ADD/ 
WQ and learning disabilitiaa (Hynd, Larys, et al., 
1991) and between children with ADD& and co- 
morbid disorders assaciacted with externalizing 
behaviors (e,g,, cond~@t disorder, oppositional defi- 
ant disorder; Lahey et d., 1987). 
Respite the, pvblichtion of DSM-III-R in 1987, 
it has taken a deosldle far sufficient research to be 
published whiclh addresi$es adequately the behav- 
ioral and nle~rcupsy~halogi~~l differentiation of 
ADDM and &S)D/WO. This literature should 
provide the basis for some conclusions as to the 
theoretical and clinical relevance of the notion that 
ADD subtypes exist. 
A second purpose af this article is to review the 
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SUBTYPES OF ADD 
Table 1. Criteria for Diagnosing ADDs 
Criteria for ADD/H ADD/WO ADHD UADD 
Diagnosis (DSM-III) (DSM-IIZ) (DSM-111--R) (DSM-111-R) -- 
Inattention 
Impulsivity 
Hyperactivity 
At least 8 of the following 14 symptolns 
X X are present: X 
(3) Is easily distracted by extraaeous 
stimuli. 
(6) Has difficulty following thropgh on 
instructions from others (not clue to 
oppositional behavior or failute of 
comprehension); e.g., fails to finish 
chores. 
(7) Has difficulty sustaining attehtion in 
tasks or play activities. 
(12) Often does not seem to listen to 
what is being said to him or her. 
(13) Often loses things necessary for 
tasks or activities at school od at home 
(e.g., toys, pencils, books, 
assignments). 
(4) Has difficulty awaiting Iturn in games 
X or group situations. 
(5) Often blurts out answers to questions 
before they have been complTed. 
(8) Often shifts from one uncompletrd 
activity to another. 
(9) Has difficulty playlng quietly. 
(1 1) Often interrupts or intrude$ on 
others; e.g., butts into other qhildren's 
games. 
(14) Often engages in physically 
dangerous activities without 
considering possible consequences. 
(1) Often fidgets with hands or feet or 
squirms in seat. 
(2) Has difficulty remaining seated when 
required to. 
(10) Often talks excessively. 
Onset before age 7 X X X 
Duration of art least 6 months X X X 
Not du~e to schizophrenia, affective 
disor~der, or severe or profound 
retardation X X 
Does not meet criteria for a pervasive 
developmental disorder 
Note: Numbers denote discriminating power in data from national field trial of DSM-111-R (American Psjchiatric Association, 1987) 
criteria. 
neuro~psychological studies concerning ADD/H 
and ADDIWO. Because ADDs presumably are the 
result of neurological dysfunction and the behav- 
ioral nature of these two subtypes may be different, 
it makes c~onceptual sense that neuropsychological 
differences may exist. 
Behavioral Studies of ADDS 
Presently, 21 behavioral studies have addressed 
whether children diagnosed with ADD/H or ADD/ 
WO can be differentiated; these are summarized in 
Table 2. This section atfdressets clirical and method- 
ological issues and sunimari~es tlhe results of these 
behavioral studies. 
Subject Characteristics ' 
Sample size. Overall, beihavl~oral studies have 
contrasted 692 ADD/H children with 481 ADD/ 
WO children, 344 normal controls, and 166 clinic 
controls. Average sample siqe for these studies is 
32.9 for ADD/H and 22.9 for A,DD/WO. These 
averages, however, ar~e somewhist misleading be- 
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Table 2. Behavioral Studies of Children Diagnosed as Having ADD/H or ADD/ WO 
Author(s) N Differential Diagnosis Behavioral Measures Results 
Dykman et al. (1980) 43 males Co-Occurring Diagnoses: 1. Standard, double-blind, cross-over-de- 1. ADDAVO improved significantly more 
ADD/H: n = 15 All subjects referred for school-related aca- sign drug study with methyfphenidate. in search rate than ADD/H group. 
ADD/WO: n = 11 demic and behavioral difficulties. 2. Pribram task, measure of sustained atten- 2. ADD/WO subjects received lowest lev- 
Clinical Controls: Operational Criteria: tion scored for search and solution rates. els of methylphenidate but registered 
Reading disabled (RD): n = 1 1 1. Hyperactivity = Raw score 2 15 on greatest improvement in search rate. 
Reading disabled and hyperactive (RD/H): Abbreviated Teachers' Conners 
Raw Score 
ADD/H 22.3 
RD/H 20.3 
RD 6.4 
A D D N O 7.3 
and 
Parent Interview 
corroborating history of 
management problems. 
2. FSIQ2 90. 
3. Not on medication at 
time of initial ratings. 
Maurer & Stewart 297 subjects (225 male, 72 female) Co-Occurring Diagnoses: 
(1980) Meeting criteria for ADD = 166 5/9 LD 
ADD/H: n = 114 (95 male, 19 female) 3/9 encopretic 
Conduct disordered: n = 34 1/9 conduct disordered 
Depression: n = 3 Operational Criteria: 
Adjustment reaction: n = 1 1. ADD/WO = 
Autism: n = 2 a. History of problems with short at- 
Schizophrenia: n = 1 tention span. 
Hyperthyroidism: n = 1 b. Difficulty finishing school work or 
Undiagnosed: n = 2 projects. 
ADD/WO: n = 9 (7 male, 2 female) c. DSM-111 criterion of impulsive- 
None; study conducted on basis of retro- Chart review showed: 
spective chart review. 1. 5/9 rated as having short attention 
span. 
2. 5/9 rated as lacking motivation. 
3. 5/9 rated impatient. 
4. 1/9 rated impulsive. 
5. None rated as fighting. 
King & Young (1982) 58 males 
ADD/H: n = 22 
A D D N O : n = 9 
Normal controls: n = 27 
ness not required. 
2. No IQ criterion. 
3. Status of medication not reported. 
Operational criteria: Teacher Perceptions: Teacher Perceptions (using Conners 
1. SNAP Checklist-Teacher: ADD/H 1. Conners Teacher Rating Scale (39- Teacher Rating Scale): 
= rating of very much or pretty item version). 1. ADD/WO differed from control 
much or at least (a) 2 hyperactivity 2. Likert scale concerning academic group only on inattention. 
symptoms and (b) 3 inattention progress. 2. ADD/H and ADD/WO groups did 
symptoms. ADD/WO = at least Peer and Self-perceptions: not differ on Inattention factor. 
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Edelbrock et al. 87 males 
(1984) ADD/H: n = 18 
ADD/WO: n = 7 
Clinical controls: n = 62 
one rating of pretty much or very 
much for both inattention and im- 
pulsivity combined; no ratings of 
very .-uc!: m d x~ mere thax gne rat 
ing of pretty much on hyperactivity 
symptoms. 
2. Not on medication at time of ratings. 
3. Average scaled score on WISCR 
vocabulary. 
Co-Occurring Diagnoses: 
No exclusions for LD/BD required. All sub- 
jects referred for mental health services. 
Operational Criteria: 
1. Independent diagnostic agreement 
by two child psychiatrists reviewing 
case histories. 
2. No IQ criterion. 
3. Medication status unreported. 
Lahey et al. (1984) 50 subjects (36 male, 14 female) Co-Occurring Diagnoses: 
ADD/H: n = 10 (9 male, 1 female) Overlapping conduct disorders in 8/10 
ADD/WO: n = 20 (13 male, 7 female) ADD/H subjects. 
Normal controls: n = 20 (14 male, 6 fe- Operational Criteria With RBPC: 
male) 1. All ADD subjects scored 2 1 stan- 
dard deviation above mean ( 2 12) 
on Attention Problem-Immaturity 
factor. 
2. ADD/H also scored 2 1 standard 
deviation above mean ( 2 5) on 
Motor Excess factor. 
3. No IQ criterion. 
4. No report on status of medication. 
Rubenstein & Brown 46 subjects (39 male, 7 female) 
(1984) ADD/H: n = 23 
ADD/WO: n = 23 
Operational Criterion: 
Two GZpendent TaTers s se fved and rated 
subjects' behavior during interaction with 
staE member in structured, ciassroomiike, 
task-oriented setting. Kappa interrater reli- 
abilities: ADD/WO = .50 (fair to good); 
ADD/H = .37 (fair to poor) 
1. Sociometric measure completed by 
entire class. 
2. L ie r t scale to measure accuracy of 
. .nm&.roA ..r\...r1.3&+.. -..A o,.nAnm:n yL'-'.LU y"y"'U""j ','all '4""U.c.ll'r 
ability. 
3. Preschcc! and Primary Self-Concept 
Scale. 
Teachers completed the Teacher Report 
Form of the Child Behavior Checklist 
(Achenbach & Edelbrock, 1983). 
1. Teacher ratings on four RBPC factors 
which had not been used to identify the 
two experimental groups: 
a. Conduct Disorder. 
b. Socialized Aggression. 
c. Anxiety-Withdrawal. 
d. Psychotic Behaviors. 
2. Classroom teachers: Likert scale of 
sports performance. 
3. Physical education teachers: Likert scale 
of sports performance. 
4. Sociometric and peer measures. 
5. Self-report measures 
a. cnI. 
b. Piers-Harris test (P-H). 
Attention and Impulsivity Measures: 
Matchinz -Famifiaf Tigutes Test (MFF"ff 
children's Checking ask (CCT) 
Embedded Figures Test 
Attention-Concentration factor of WISC-R 
(arithmetic, digit span, coding) 
Academic Achievement: WRAT 
Detroit Tests 
3. ADD/H > ADD/WO on hyperac- 
tivity. 
4. ADD/H > ADD/WO on conduct 
..rr\l.lnmc 
""'L"'". 
5. Findings suggest ADD/WO may be 
independent of conduct disorders. 
Peer and Self-Perceptions: 
Both hDD/H and ADD/WO children 
perceived more negatively by peers than 
were controls on sociometric measures. 
1. ADD/WO > ADD/H: Social With- 
drawal. 
2. ADD/H > ADD/WO: (a) Unpopular, 
(b) Self-Destructive, (c) Nervous-Over- 
active, and (d) Aggressive. 
3. ADD/H > ADD/WO and control 
groups on behavior problems. 
4. ADD/WO < ADD/H on current 
school performance. 
5. ADD/WO > ADD/H in grade repeti- 
tions. 
1. ADD/H r Control: 
a. Conduct Disorder. 
b. Socialized Aggression. 
c. Psychotic Behaviors. 
2. ADD/N < Control on academics. 
3. ADD/WO > Control on Anxiety-With- 
drawai. 
4. ADD/WO < Control on academic and 
sports performance. 
In discriminant analyses, only TRSI re- 
tain&. the of TRSI to classify children as 
ADD/WO or ADD/H was only slightly 
- --- --- --L- .LA- ..--An- ..I,."":&."*:,.- 
IIIUIC aLLuIaLC luau l a u u u i u C~DUIIIC. ( ILIUII . 
(Continued) 
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Table 2. (Continued) 
Author(s) N Differential Diagnosis 
Berry et al. (1985) 228 subjects (164 male, 64 female) 
ADD/H: n = 94 (72 male, 22 female) 
ADD/WO: n = 40 (30 male, 10 female) 
Normal controls: n = 94 (62 male, 32 fe- 
male) 
Borden et al. (1985) Same sample as Rubenstein & Brown 
(1984). Nine subjects for whom complete 
data were not available were eliminated 
from analysis; therefore 37 subjects re- 
mained. 
Co-Occurring Diagnoses: 
Male Female 
Learning disability 63% 50% 
Reading disorder 53% 41% 
Math disorder 34% 25% 
Expressive language 
disorder 24% 28% 
Receptive language dis- 
order 7% 9% 
Exclusions: 
1. IQ < 70. 
2. Age < 6 years. 
3. No psychosis. 
Operational Criteria: Comprehensive 
neurological, behavioral, and psycho- 
educational evaluation. Children were 
selected who met DSM-IZI criteria for 
ADD. 
Same sample as Rubenstein & Brown 
(1984). 
Lahey et al. (1985) 50 subjects (36 male, 14 female) Co-Occurring Diagnoses: Based on teacher 
ADD/H: n = 10 (9 male, 1 female) ratings on RBPC. Students had mild to se- 
ADD/WO: n = 20 (13 male, 7 female) vere behavior or social problems. Overlap- 
Normal controls: n = 20 (14 male, 6 fe- ping conduct disorders in 8/10 ADD/H 
male) subjects. 
Operational Criteria With RBPC: 
Behavioral Measures Results 
Durrell Reading Test 
Behavior Rating Scales: Abbreviated Con- 
ners (Teacher and Parent forms) 
Teacher Rating Scale of Attention (TRSA) 
Teacher Rating Scale of Impulsivity (TRSI) 
Yale Children's Inventory (Parent rating 
scale): 7 behavioral scales for ADD 
Attention 
Impulsivity 
Tractability 
Habituation 
Conduct Disorder 
Aggressive 
Negative Affect 
3 cognitive scales 
Academic 
Language 
Fine Motor 
Matching Familiar Figures Test (MFFT; 
error score) 
WISC-R: Arithmetic Coding 
WRAT-Arithmetic 
Children's Checking Task (CCT) 
Conners Teacher Abbreviated Rating Scale 
Conners Parent Abbreviated Rating Scale 
Teacher Rating Scale of Attention 
Family Life Questionnaire 
Item analysis of 16 items of Attention Prob- 
lems-Immaturity scale of RBPC. 
Reason for Referral: 
1. Poor schoolwork (females, 87%; 
males, 75%). 
2. Behavior problems at school or 
home (M -- F). 
Conclusions: 
1. ADD males and females have simi- 
lar profiles; however, ADD in 
females associated with more severe 
cognitive, language, and social defi- 
cits. 
2. Factor analysis of Yale inventory 
yields: 
a. Attentional/Cognitive factor. 
b. Attention/Behavioral factor. 
Stepwise discriminant analysis yielded a sig- 
nificant discriminant function including 5 
variables:WRAT-Arithmetic 
WISC-R: Arithmetic Coding 
Several Teacher Ratings of Attention 
Use of the resulting discriminant function 
resulted in correct classification of 70% of 
subjects. 
1. ADD/H > ADD/WO: 
a. Irresponsibility. 
b. Distractibility. 
c. Impulsivity. 
d. Answering Without Thinking. 
e. Sloppiness. 
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Ackerman, Anhalt, 93 males 
Dykman, & Holcomb ADD/H: n = 24 
(1986) ADD/WO: n = 21 
Reading Disabled (RD): n = 24 
Normal controls: n = 24 
Ackerman, Anhalt, 93 males 
Holcomb, & Dykman ADD/H: n = 24 
(1986) ADD/WO: n = 21 
Reading disabled (RD): n = 24 
Normal controls: n = 24 
1. All ADD/H scored 2 1 standard 
deviation above mean (2 5) on 
Motor Excess factor. 
2. No IQ criterion. 
3. No report on status of medication. 
Co-Occurring Diagnoses: 
Experimental subjects referred for behavior 
problems or learning disabilities. 
Operational Criteria: 
1. ADD groups defined on basis of 
Conners teacher ratings. 
2. Exclusion of subjects whose VIQ and 
PIQ were both < 90. 
3. Not on stimulant medication at time 
of ratings. 
Co-Occurring Diagnoses: 
Experimental subjects referred for behavlor 
problems or learning disabilities. 
Operational Criteria: 
1. DSM-111 criteria employed in defi- 
nitions of ADD/H and A D D N O . 
2. ADD groups defined on basis of 
Conners teacher ratings. 
3. Exclusion of subjects whose VIQ and 
PIgwere bath < 90. 
4. Not on stimulant medication at time 
of ratings. 
Semantic and acoustic encoding: 
1. Free, acoustic. 
2. Free, semantic. 
3. Cued, acoustic. 
4. Cued, semantic. 
List learning of high- and low-imag- 
ery words: 
1. Learning, Hi. 
2. Learning, Lo. 
3. Delayed, Hi. 
4. Delayed, Lo. 
Memory for 12 printed words: 
1. Look. 
2. Study. 
3. Cluster. 
Computation: 
1. Paper, correct. 
2. Computer, correct. 
3. Paper, latency. 
4. Computer, latency. 
1. Frequency-of-occurrence sensitivity. 
2. Temporal sensitivity. 
3. Speed of naming drawings of objects. 
4. Speed of writing 0's and name. 
5. Accuracy with number facts: 
a. Paper. 
b. Computer, nonreward. 
6. Speed with number facts: 
a. Paper. 
b. Camputer. 
c. Computer with reward. 
2. ADD/WO > ADD/H: 
a. Sluggishness. 
b. Slowness. 
ANCOVA results varying for IQ (for task 
with the corresponding number in previous 
column). 
Semantic and acoustic encoding: 
1. No differences. 
2. No differences. 
3. RD < Control, ADD/H. 
4. RD < ADD/WO. 
Hi-Lo imagery: 
1. Control > ADD/WO. 
2. Control > all. 
3. No differences. 
4. Control > all. 
Memory for words: 
1. No differences. 
2. Control > all. 
3. No differences. 
Computation: 
1. Control > all. 
2. Control > all. 
3. Control, RD < ADD/WO. 
4. No differences. 
1. Frequency sensitivity: No differences. 
2. Naming (time): Young subjects-no dif- 
ferences; old subjects-ADD/H > Con- 
trol and RD. 
3. Writing (time): Young subjects-no dif- 
ferences; old subjects-ADD/ WO sig- 
nifcantly less productive than ADD/H, 
RD, and Control groups. 
4. Stepwise regression analysis exploring re- 
latian of data set to ADD Index con- 
cluded that ADD/WO and RD children 
do not have basic math hcts sutoms- 
tized; mean latencies in solving basic 
math facts yielded the strongest single 
predictor of the ADD/WO Index. 
(Continued) 
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Table 2. (Continued) 
Author(s) N 
Brown (1986) 146 subjects 
ADD/H: n = 88 (75 male, 13 female) 
ADD/WO: n = 58 (51 male, 7 female) 
Carlson et al. (1986) 51 subjects 
ADD/H: n = 20 
ADD/WO: n = 15 
Normal controls: n = 16 
Conte et al. (1986) 24 subjects (18 male, 6 female) 
ADD/H: n = 8 (6 male, 2 female) 
ADD/WO: n = 8 (7 male, 1 female) 
Normal controls: n = 8 (5 male, 3 female) 
Differential Diagnosis 
Co-Occurring Diagnoses: 
All subjects referred to a university clinic for 
behavior problems including restlessness, 
distractibility, short attention span, and 
poor impulse control. 
Operational Criteria: 
1. Onset of disorder prior to 7 years. 
2. Differential diagnosis into ADD/H 
and ADD/WO groups based on in- 
dependent judgments of two raters. 
3. No IQ criterion given but psycho- 
metric data provided. 
4. Not on medication at time of ratings. 
Co-Occurring Diagnoses: 
All experimental subjects recruited from re- 
source programs for LD and BD students. 
Operational criteria: 
Groups defined on basis of SNAP by 
teacher: 
1. ADD/H had ratings of pretty much 
or very much on: 
a. 2 2 hyperactivity symptoms. 
b. 2 3 inattention symptoms. 
c. 2 3 impulsivity symptoms. 
2. ADD/WO had ratings of pretty 
much or very much on: 
a. < 2 hyperactivity symptoms. 
b. 2 3 inattention symptoms. 
c. 2 3 impulsivity symptoms. 
3. WISC-R FSIQ > 80. 
Co-Occurring Diagnoses: 
Both experimental groups at least 2 years 
below grade level in reading, spelling, and 
math. All enrolled in learning-disabilities re- 
medial classes. 
Operational Criteria: 
1. DSM-111 symptom checklists. 
2. Revised Conners Teacher Rating 
Scale 
3. WISC-R IQs > 85. 
4. Not on medication at time of ratings. 
Behavioral Measures Results 
10-item Abbreviated Conners Rating Scale 1. Teachers rated ADD/H children as 
completed by teachers. more problematic. 
2. Three factors emerged: 
a. Emotional Lability/Conduct. 
b. Temperament. 
c. Attention-Concentration. 
WISC-R 
CELF 
VMI 
BASIS 
Rapid Naming Task 
Visual Match-to-Sample Task 
Detroit: Visual Attention Span 
Stroop Color Distraction 
WISC-R: 
1. FSIQ: ADD/WO (98.87) > 
ADD/H (90.70). 
2. VIQ: ADD/WO (99.64) > ADD/H 
(85.40). 
Timed tasks (Rapid Naming, Stroop): 
Controls faster than ADDs. 
Achievement: 
Controls > ADD/WO on math 
achievement. 
Visual Match to Sample: 
Controls > ADD/WO. ADD/H: No 
differences with controls or A D D N O . 
Matching Familiar Figures Test (MFFT) MFFT: 
Paired-Associate Learning Task (PA) 1. ADD/H latencies > ADD/WO la- 
tencies. 
2. ADD/WO subjects more impulsive 
than ADD,% subjects. 
PA: - 
ADDs did not benefit from extra study 
time on fixed-rate lists. 
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Carlson et al. (1987) 72 subjects 
(predominantly male and Caucasian) 
ADD/H: n = 16 
ADD/WO: n = 11 
Normai controls: n = 45 
Lahey et al. (1987) 63 subjects 
(predominantly male and Caucasian) 
ADD/H: n = 41 
ADD/WO: n = 22 
Lahey et al. (1988) 1. N = 667 nonreferred children. 
2. N = 86 consecutive referrals to GCC. 
ADD/H: n = 41 
ADD/WO: n = 22 
Clinic Controls: n = 23 
rommer, Hoeppner, 78 subjects 1 osenberg, Arm- ADD/H: n = 36 
Etrong, & K~ths te~n 4DD/U!O: n = 12 
(1988) Controls: n = 30 
Exclusions: 
Co-occurring diagnoses except mild, non- 
disabling simple phobias excluded. 
Operational Criteria: 
1. Children's version of Schedule for 
Affective Disorders and Schizophre- 
nia (K-SADS) conducted in inter- 
view format with teacher, parent, 
and child. 
2. Rating scales were completed by 
parents and teachers. 
Co-Occurring Diagnoses: 
1. ADD/H: 56% conduct disorder; 
10% Internalizing disorder. 
2. ADD/WO: 36% conduct disorder; 
43% internalizing disorder (anxiety 
or depressive). 
Exclusions: 
1. FSIQ < 70. 
2. Neurological disorder. 
3. Psychotic disorder. 
Operational Criteria: 
1. Children's version of Schedule for 
Affective Disorder and Schizophre- 
nia (K-SADS) conducted in inter- 
view format with teacher, parent, 
and child. 
2. Rating scales were completed by 
parents and teachers. 
Operational Criteria: 
1. Children's version of Schedule for 
Affective Disorder and Schizophre- 
nia (K-SADS) conducted in inter- 
view format with teacher, parent, & 
child 
2. Rating scales were completed by 
parents and teachers. 
Suhects were me&cally dentrfied No child 
was taklng stimulant or other medication 
mfluencing deep. 
Sociometric measures administered by class- 
room teachers. Children were asked to write 
down privately the names of 3 children liked 
most (LM), 3 childrenliked least (LL), and 
3 who fought most. 
Behavioral Ratings: 
Conners Teacher Rating Scale (TRS) 
Child Behavior Rating Scale 
Children's Depression Inventory 
Trait Anxiety Scale 
SNAP 
RBPC 
Structured Interview: 
K-SADS 
1. Teachers asked to rate children on 
SNAP. 
2. Clinicians rated children on 20 descrip- 
tors of ADHD: 13 drawn from DSM-IIL 
2 from DSM-111-R, and 5 items as- 
sociated with ADD/WO (sluggish, 
drowsy, absent-minded, daydreams, dis- 
turbs others). 
ParentalQyestjamire to determine the 
prevalence of sleep disorders at present (last 
3 to 12 nonths> and in retrospect (last ! to 
4 years). 
1. Normals > ADD/H and A D D N O on 
Liked Most and Social Preference (i.e., 
LM - LL). 
2. Normals < ADD/H and ADD/WO's 
on Least Liked. 
3. No differences between ADD/H ADD/ 
WO. (However, when ADD/H ADD/ 
WO children with co-diagnoses were in- 
cluded in the analysis, ADD/H > 
ADD/WO and normals on Fights Most.) 
Teacher Ratings: 
1. Conduct problems: ADD/H > 
ADD/WO. 
2. Impulsivity: ADD/H > ADD/ 
WO. 
3. Sluggish, cognitive tempo: ADD/ 
WO > ADD/H. 
4. Fighting: ADD/H > ADD/WO. 
5. ADD/WO more likely to display in- 
ternalizing disorders. 
1. SNAP yielded two factors: 
a. Inattention/Disorganization. 
b. Motor Hyperactivity/Impulsivity. 
2. Clinician-completed descriptors of ADD 
yielded three factors: 
a. Motor hyperactivity/Impulsivity. 
b. Inattention/Disorganization. 
c. Sluggish Tempo. 
ADDS Versus Controls: 
Significantly more parents of ADDS re- 
ported children having ti~db!e fa!!iiig asleep 
and feeling tired upon awakening. 
ADD/H Versus A D D N O : 
1. ADD/H had greater nocturnal 
arousal than ADD/WO. 
2. ADD/WO had greater morning re- 
call of nightmares than ADD/H. 
(Continued) 
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Table 2. (Continued) 
Author(s) N Differential Diagnosis Behavioral Measures Results 
- 
Barkley et al. (1990) 142 subjects Co-Occurring Diagnoses (%): Parental Source: Parental Interview: 
ADD/H: n = 42 (39 male, 3 female) Structured Interview 1. LD more likely to have experienced 
ADD/WO: n = 48 (43 male, 5 female) ADD/H ADD/WO LD Vineland Adaptive Behavior Scale language delay. 
LD: n = 16 (12 male, 4 female) ADHD 92.9 31.3 0.0 Child Behavior Checklist (CBCL) 2. ADD/H (40%) and A D D N O 
Normal controls: n = 36 (35 male, 1 fe- ODDa 40.5 18.8 0.0 Home Situations Questionnaire (HSQ) (54%) children have fair to poor 
male) CD a 21.4 6.3 0.0 Revised Conners Parent Rating Scale motor coordination significantly 
SAD a 9.5 6.3 0.0 Beck Depression Inventory more often than LD. 
OAD a 0.0 0.0 6.3 Symptom Checklist-Revised (SCL-9CR) 3. Significantly more ADD/H children 
MDD a 0.0 2.1 0.0 Locke-Wallace Marital Adjustment reported to have been treated with 
L D ~ R ~ ~ . 19.0 18.8 18.8 Life Stress scale from Parent Stress Index individual or family therapy and 
L D ~ s ~ ~ . 23.8 22.9 3 1.3 Teacher Source: placed in special education for be- 
~ ~ ~ ~ a t h 26.2 20.8 3 1.3 Child Behavior Checklist-Teacher Report havior disorders. 
Form (CBCL-TRF) 4. Significantly more A D D N O than 
(aNote: ODD = oppositional defiant dis- School Situations Questionnaire ADD/H children in LD placements. 
order, CD = conduct disorder, SAD = sep- ADHD Rating Scale 5. ADD/H significantly more paternal 
aration anxiety disorder, OAD = overanx- Taxonomy of Problem Situations (TOPS) relatives with attention deficits and 
ious disorder, MDD = major depressive Psychological Tests: hyperactivity and maternal relatives 
disorder.) WISC-R with substance-abuse problems than 
(b~ote : LD defined as score below 7th %tile WRAT-R other groups. 
on achievement and significant discrepancy Continuous Performance Test (CPT) 6. Both ADD/WO and LD groups 
between IQ and achievement on that test.) Kagan Matching Familiar Figures Test more likely to have siblings with LD 
(MFFT) than ADD/H or normal groups. 
Parental Behavior Ratings: 
1. ADD/H significantly worse than 
ADD/WO and other groups on 
number of problem settings (HSQ) 
and Aggressive and Delinquent 
scales (CBCL). 
Behavioral Observations: 2. ADD/WO significantly worse than nor- 
1. ADHD behaviors during math prob- mals on Depressed, Uncommunicative, 
lems task (off-task, fidgets, out-of- Obsessive-Compulsive, Somatic Com- 
seat). plaints, Social Withdrawal, Aggressive, 
2. ADHD behaviors during CPT test- and Delinquent scales of the CBCL. 
ing. Teacher Behavior Ratings: 
3. Wrist and ankle actometers. 1. ADD/H worse than ADD/WO on 
pervasiveness, aggression, and self- 
destructive behaviors. 
2. A D D N O worse than LDs or con- 
trols in 14 of 16 behavioral areas 
rated by teachers with exceptions in 
aggressiveness and problem situa- 
Operational Criteria: 
1. For ADD/H: 
a. Maternal complaints of short at- 
tention span, impulsivity, and ove- 
ractivity at school. 
b. 6-month duration of problems. 
c. Age of onset: < 7 years. 
d. Child Attention Profile (CAP) 
scores > 93rd %tile on both Inat- 
tention and Overactivity scales. 
e. No history of stimulant treatment 
or removal of medication for 48 hr 
before evaluation. 
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Hynd, Lorys, et al. 20 subjects 
(1991) ADD/H: n = 10 (9 male, 1 female) 
ADD/WO: n = 10 (8 male, 2 female) 
Barkley et al. (1991) 40 subjects 
ADD/H: n = 23 (21 male, 2 female) 
ADD/WO: n = 17 (15 male, 2 female) 
2. For ADD/WO: 
a. Same as criteria a, b, c, and e for 
ADD/H. 
b. CAP scores > 93rd Yotile on Inat- 
tention scale and < 84th %tile on 
Overactivity scale. 
3. For LD: 
a. Referral for academic learning 
problems or current school LD 
placement. 
- - - - - - - -- - - - - - - - - - 
b. Teacher complaints of math, 
handwriting, or language. 
c. No teacher complaints of matten- 
tion, overactivity, or impulsivity. 
d. CAP scores < 84th %tile on both 
Inattention and Overactivity 
scales. 
Co-Occurring Diagnoses: 
1. ADD/H: 40% conduct disordered. 
2. ADD/WO: 60% developmental 
learning disorders. 
Excluslons: 
1. FSIQ < 70. 
2. Epilepsy. 
3. Closed head injury. 
4. Other neurological disorder. 
Operational Criteria: 
1. WISGR: FSIQ > 70. 
2. K-SADS: Parent and teacher. 
3. Parent and teacher behavior rating 
scales (CBCL; SNAP). 
Co-Occurring Diagnoses: 
Not reported. 
Operational Criteria: 
Same as Barkley et al. (1990). 
Excluslons: 
SameeasBar&p etal.-(l99Dkplus the fol- 
low~ng further exclusions: 
1. Childieii with history of tics oi T~i i - 
rette's. 
2. Chlldren with history of cardiac sur- 
gery, high blood pressure, or cere- 
bral vascular accident. 
Academic Achievement: 
BASIS: Math, Reading, Spelling 
Behavioral Adjustment: 
SNAP: Hyperactivity, Inattention, and Im- 
pulsivity 
PIC: Social Skills 
Psychological Tests: 
1. Verbal learning and memory: Wis- 
consin Selective Reminding Test 
(WSRT). 
2. Vigilance: CPT. 
Zlmpulse e~ntml: KaganMEFT. 
4. Behavior observations during math 
pioblems. 
Parent Behavior Ratings: 
1. Home Situations Questionnaire 
(HSQj. 
2. ADHD Rating Scale. 
tions with peers. ADD/WO children 
had no more peer relational diffi- 
culties than controls but were worse 
than LDs in this area. 
3. ADD/H > ADD/WO on Inatten- 
tiveness scale of CBCL-TRF. 
4. ADD/WO > ADD/H on Inatten- 
tiveness scale of CBCLTRF. 
Academic Achievement: 
BASIS Math: ADD/H > ADD/WO. 
Behavioral Adjustment: 
1. SNAP: 
a. Hyperactivity: ADD/H > ADD/ 
WO. 
b. Inattention: No difference. 
c. Impulsivity: ADD/H > ADD/ 
wo. 
2. PIC: ADD/H significantly more dis- 
turbed than ADD/WO based on 
parent ratings. 
Parent Behavior Ratings: 
1. ADD/H worse than ADD/WO on 
number of problem settings on HSQ. 
2. Main effect for drug condition in- 
dicating significant declines on: 
a. HSQ-Xumber of problem set- 
tings and mean severity scores 
with high doses (relztive to pla- 
cebo). 
b. ADHD Rating ScaleTota l score 
and number of significant symp- 
toms with all three doses (relative(Continued) 
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Table 2. (Continued) 
Author(s) N Differential Diagnosis Behavioral Measures Results 
3. Children with history of adverse re- 3. Home Side Effects Rating Scale. 
actions to stimulants. Teacher Behavior Ratings: 
Operational Criteria: 1. School Situations Questionnaire 
Same as Barkley et al. (1990). (SSQ). 
2. CAP. 
3. Teacher Self-Control Rating Scale 
(TSCRS). 
4. School Side Effects Rating Scale. 
to placebo, high doses, however, 
produced a significantly greater 
reduction than did low doses). 
Teacher Behavior Ratings: 
1. ADD/H worse than ADD/WO on 
CAP, SSQ, and TSCRS. 
2. Main effect for drug condition in- 
dicating significant declines on: 
a. CAP-Inattention with moderate 
and high doses. 
b. CAP-Overactivity with all three 
doses. 
c. SSQ-Number of problem set- 
tings and mean severity score at 
school reduced with all three 
doses. 
3. Main effect for drug condition shows 
significant improvement in self-con- 
trol of both groups with all three 
doses. 
Note: ANCOVA = analysis of covariance; BASIS = Basic Academlc Skills Individual Screener; CCT = Children's Checking Task; CDI = Ch~ldren's Depression Inventory; FSIQ = Full Scale Intelligence 
Quotient; GCC = Georgia Children's Clinic; LD/BD = Learning Disabled/Behavior Disordered; PA = Picture Arrangement; PIC = Personality Inventory for Children; PIQ = Performance Intelligence 
Quotient; PPVT = Peabody Picture Vocabulary Test; RBPC = Revised Behavior Problem Checklist; VIQ = Verbal Intelligence Quotient; VMI = Test of Visual-Motor Integration; WISC-R = Wechsler 
Intelligence Scale for Children-Revised; WRAT = Wide Range Achievement Test. References for certain tests mentioned in table may be found in the relevant study. 
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SUBTYPES ( )F ADD 
cause IMaurer and Stewart's (1980) epidemiological 
study accounted for 16% of the total ADD/H sam- 
ple. A more realistic picture of the average sample 
size, then, is gained by excluding the Maurer and 
Stewart's (1980) retrospective case review. This re- 
sults irk an average sample size of 28.9 children with 
ADD/IH and 23.6 children with A D D N O per 
study. 
One: conclusion that can be drawn from these 
data, c~nsis~tent with that of Carlson (1986), is that 
relatively few children with ADDSWO have been 
studiecl. This problem is further compounded by 
recognition that the same subjects were used in sev- 
eral pairs of stuldies: Lahey et al. (1984) and Lahey 
et al. (1985); Lahey et al. (1987) and Lahey et al. 
(1988); Barkley et al. (1990) and Barkley, DuPaul, 
and NIcMurray (1991); and Ackerman, Anholt, 
Dykmjm, and FI01c0mb (1986) and Ackerman, An- 
holt, IIolcomb, and Dykman (1986). Further, re- 
view of the subject descriptions in Rubinstein and 
Brown (1984) and Brown (1986) suggests the possi- 
bility of sample overlap in these studies as well. If 
this is the case, the total number of ADDJWO chii- 
dren sl.udied may be as low as 395. 
Sex distribution. Subject populations in these 
studies havie been predominantly male, making up 
91.5% of the t01,al sample. Five studies (Ackerman, 
Anhall., Dykman, & Holcomb, 1986; Ackerman, 
Anhalt, Holcomb, & Dykrnan, 1986; Dykman et al., 
1980; Edelbrock et al., 1984; King & Young, 1982) 
have investigate~d exclusively male samples. On the 
other hand, five studies have included a much 
larger-thamaverage female sample (Berry, S. E. 
Shaywitz, 8c B. A. Shaywitz, 1985; Conte, Kins- 
bourne, Swansan, Zirk, & Sarnuels, 1986; Lahey et 
al., 19185; 1,ahey et al., 1984; Maurer & Stewart, 
1980). Interestingly, the Maurer and Stewart (1980) 
and Conte et al. (1986) studies did not distinguish 
between ADD/H and ADD/WO groups whereas 
Lahey et a1 (1985), Lahey et al. (1984), and Berry 
et al. (1985) did, It is unknown how selection of an 
unusually large proportion of girls in these studies 
may hove aEectd outcomes. 
It is noteworthy that the Lahey et al. (1984,1985) 
subjects were experimentally classified using the Re- 
vised ELehavior Problem Checklist (Quay & Peter- 
son, 1983) rather than drawn from a clinic papula- 
tion. This may suggest that althou6h there are girls 
with ADD in the school setting, they are less likely 
to be referred than are boys with ADD. Such a 
conc1ua;ion agrees with Berry et al. ('985) who ex- 
press concern that there is a risk in underidentifying 
ADD girls without impulsivity. 
Chronological age. Ages of subjects participat- 
ing in tlhese behavioral studies range from 6.3 to 13.2 
years. The average age is 9.4 years for ADD/H and 
9.8 years for ADD/WO samples. 'The first conclu- 
sion that can be drawn from the ,age data is that a 
very narrow age range has beep studied. The second 
conchaion is that on tlhe average A D D N O chil- 
dren studied are appro:~imately M year older than 
ADD/H children. This tendency for ADD/WO 
subjects to be older thain ADD/H subjects suggests 
that A D D N O may be identified and/or referred 
later than ADDJH, as many of these subjects were 
from clinic-referred populatiops. This conclusion is 
consistent with Lahey et al. (1985')t who claim that 
children with ADD/H may b~ identified at younger 
ages because they are more ?otic:sable and create 
more distress for parents and teaclhers. 
Clinical versus nonl-eferre! samples. Samples 
for the behavioral studies emaQated from both clini- 
cal and nonreferred sources. ~ $ e vast majority of the 
studies were based on clinical +amples. On the other 
hand, several studies that ibitially diffferentiated 
ADDJH and ADDIWO groubs and proved heuris- 
tically valuable to this area of research were based 
largely on nonreferred subjectis. Lahey et al. (1984) 
and Lahey et al. (198S) exp#rime:ntally idientified 
ADD/H and A D D N O chil$ren from schwlwide 
teacher ratings of behavior. Tqis approach may well 
have included clinical subjects but was not limited 
to them. I 
Psychometric data. Psydborrietric data were 
collected on subjects in the majority of the behav- 
ioral studies (see Table 2). M p n IWechsler Intelli- 
gence Scale for Children-IRevised (WISC-R; 
Wechsler, 1974) scores were as follows: Verbal IQ 
(VIQ), 97.0 for ADDJH an 97.3 for ADD/WO 
childre& Performance 19 ( P h ) , 98.7 for ADD/H 
and 99.5 for ADD/WO clxildrkn; and Full Scale IQ 
(FSIQ), 102.01 for ADID/H 102.23 for ADD/ 
WO children. Only two et all., 1986; 
Dykman et al., 1980) 
ences between the 
In both cases, ADD/WO chpdren were found to 
have higher FSIQs than ADDqH children. The gen- 
eral conclusion that IQ clifFererjces between ADD/H 
and ADDIWO have not bedn significant (Hynd, 
Lorys, et al., 1991) is s ~ u ~ ~ o r t i d . 
Methodological Issues I 
Next, our discussion will focus on methodolo- 
gical issues related to behavioial studies of ADDS. 
Among the issues to be addressed are experimental 
design, diagnostic criteria for ADD/H and ADD/ 
WO, and the dependent measui-es employed in these 
studies. I 
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SUBTYPES OF ADD 
was solme variation, however, in how ADD/WO 
was defined (see Table 2). Dykman et al., for in- 
stance, required a parental interview to corroborate 
teacher ratings and developed additional ADD/WO 
requirements of dawdling or failure to complete 
classwork or homework not due to poor achieve- 
ment. 'Two important problems with this identifica- 
tion procedure are evident. First, impulsivity mea- 
sures may be neglected or confounded with 
attentional ratings. Second, use of both the Conners 
Teacher Rating Scales (Conners, 1969) and the Con- 
ners Abbreviated Teacher Rating Scales (Sprague et 
al., 19'74) to identify ADD children has been criti- 
cized as inappropriate by Ullman, Sleater, and 
Spraguie (1985)and Quay, Routh, and Shapiro 
(1987), 
This is an important issue considering use of the 
Conners scales in a fifth of the current ADD stud- 
ies ancl use as sole criterion in most of those. U11- 
mann et al. (1985) criticized use of both instru- 
ments. Regarding use of the 39-item rating scale, 
they point out substantive changes in 5 of the items 
in 1973 with no subsequent factor analysis from 
Conners. They also mention that analyses by other 
researchers have resulted in different factors from 
those first identified by Conners (e.g., Cohen & 
Hynd, 1986). Of particular concern for the mea- 
surement of ADD is the Werry, Sprague, and 
Coben (1975) factor analysis which yielded a com- 
bined I-Iyperactivity-Inattentiveness factor, suggest- 
ing that ADD/H and ADD/WO cannot be differ- 
entiated with this instrument. As B. A. Shaywitz 
(1987) claimed, the Conners scales yield diagnosis 
of heteroge~ieous samples of inattentive, overactive, 
and ag,gressive children. 
Regarding the Abbreviated Conners Scale, U11- 
mann let al. (1985) indicated that only 2 of the 10 
items concern attention. Furthermore, they reported 
that wlhen using the widely accepted cutoff score of 
15 for ithis s~cale, children with ADDJWO cannot be 
identified. To complicate this problem further, they 
have recommended increasing the cutoff score based 
on recent data, a change which most likely would 
increase the inappropriateness of this scale for diag- 
nosis of AI)D/WO. 
Brown (11986) also addressed concerns regarding 
measmement with the Abbreviated Conners. He 
cautioned against reliance on total scores, conclud- 
ing that the same total score on this instrument can 
have different implications for different ADD chil- 
dren. It is possible that qualitative differences in 
attention may exist but be obscured by total score 
interpretations as Barkley et al. (1990) have found 
witb the Child Behavior Checklist (Achenbach & 
Edelbrock, 1983). Clearly, there seem to be signifi- 
cant psychometric concerns regarding the use of the 
Conners scales in the diagnosis of ADD. 
A second approach to ADD subgrouping is evi- 
dent in the King and Young (19812) and Carlson et 
al. (1986) studies. Both utilize the SNAP (Pelham, 
Atkins, & Murphy, 1981) checklist, a listing of 
DSM-111 symptoms, to define AC)ID/H and ADD/ 
WO groups. These researchers use~d identical crite- 
ria for ADD/H identilicatioa. Again, as with the 
Conners scales, researchers vary in the criteria they 
employ even when using the sarne instrument to 
identify ADDMO. The two proups of researchers 
were consistent in their definitions lolf inattention and 
impulsivity; however, Icing apd Young (1982) de- 
fined the absence of hyperactivity more strictly than 
did Carlson et al. (1986; see Table 2). 
Although some variation im the ADD/WO defi- 
nition remains with the SNAP, one problem en- 
countered by the first two ADD subgrouping ap- 
proaches is considered. Quay let al (1987), in their 
review of measurement of phildhood psychopa- 
thology, point out that none af the existing teacher 
or parent rating scales except the SNAP have a sepa- 
rate impulsivity subscale. The implication is that 
none of the rating scales excep$ the SNAP will iden- 
tify specifically subjects meeting all1 three compo- 
nents of DSM-111 criteria (i.e., cleficient attention 
and impulsivity for ADD/WO and ADD/H with 
the additional requirement of Ihyperactivity for 
ADDJH). This idea has been challlenged, however, 
by the Lahey et al. (1988) resylts. Factor analysis of 
the SNAP yielded support foronl!? two factors, one 
of which was an overlapping voter Hypteractivity/ 
Impulsivity factor. 
A third approach to ADD yubgrouping is seen in 
the research of Lahey et al. (1984, 1985). These 
investigators defined their ABD s~xbgroups experi- 
mentally using the Revised Behavior Problems 
Checklist (RBPG; Quay & Peterson, 1983). As men- 
tioned with several other appqoaches to ADD sub- 
grouping, the RBPC mary not i$clude an impulsivity 
measure. If it does, it overlaps with other measures 
such as attention or motor excess which could result 
in heterogeneous ADD ,groupi gs. Therefore, its use 
as a sole criterion for AD11 di 1 etren~tiation yields an 
incomplete or obscured meashrern~snt of the ADD 
criteria as delineated in DSML-111: 
The fourth approach ito q D I ) subgrouping is 
found in Lahey et al. (1987); Carlson et al. (1987); 
Hynd, Lorys, et al. (1991); and Lithey et al. (1988) 
for their referred samples. Parqnts itad teachers were 
interviewed using structured interviews and both 
completed the SNAP and additionla1 behavior rat- 
ings. A11 diagnostic decisions were: made indepen- 
dently by two psy~h01o~:ists afiter reviewing all psy- 
chometric and behavioral data.. All diagnostic 
criteria reflected criteria outlived in DSM-111 for 
ADD/H and ADDJWO. Any disagreements were 
resolved through mutual discussior~. Cohen's kappas 
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were computed to determine reliability of this proce- 
dure (Spitzer, Cohen, Fleiss, & Endicott, 1967). This 
approach represents an improvement over previous 
approaches in that it employs multimodal behav- 
ioral assessment. Additionally, this approach gives 
attention to the issue of reliability of clinical judg- 
ments. On the other hand, some of the behavior 
rating scales utilized may yield heterogeneous ADD 
groupings. 
The fifth approach to ADD subtyping is that of 
Barkley et al. (1990, 1991). They were the first to 
employ an empirically derived approach to identify 
their subjects. They utilized the Child Attention 
Profile (CAP; see Barkley et al., 1991) and required 
similarly high scores on Inattention but discrepant 
scores on Overactivity to distinguish ADD/H and 
ADD/WO subjects. This approach appears to be 
the most objective presently available. However, it 
relies primarily on information from teachers, which 
may violate the accepted norm of multimodal be- 
havioral assessment. 
The final approach to ADD subgrouping used in 
the behavioral studies relies on clinical judgment. 
There were three studies (Brown, 1986; Edelbrock et 
al., 1984; Rubinstein & Brown, 1984) in which the 
clinical judgment of two independent raters using 
DSM-III criteria was the criterion for inclusion in 
the study; a fourth study (Berry et al., 1985) also 
used DSM-I11 criteria whereas a fifth (Maurer & 
Stewart, 1980) did so only partially. In the Edel- 
brock et al. (1484) study, two child psychiatrists 
reviewed case histories independently and assigned 
subjects to #DD/H and A D D N O subgroups. 
Rubinstein and Brown (1984) and Brown (1986) 
based their ADD subgroupings on the independent 
judgments of two clinic staff members who observed 
and rated each subject's behavior during interaction 
with a staff member in a "structured, classroom-like, 
task-oriented settling'"Brown, 1986, p. 97). In Berry 
et al. (1985), all subjects received comprehensive 
neurological, behaviord, and psychoeducational 
evaluation that inoluded patent and teacher rating 
scales, Howevor, db diagnostic reliabilities were re- 
ported for DSM-iII diagnoses. Two immediate 
concerns with these identibation procedures are ap- 
parent. First, reliability of diagnoses is a major issue. 
Second, the effeats of a one-to-one observational set- 
ting on attentiori are of concern. 
Regarding rdiab$lity, Edelbrock et al. (1984) re- 
ported consensus diagnosis of their subjects. Lahey 
et al. (1987); Lahq et al, (1988); and Hynd, Lorys, 
et al, (1991) veported adequate reliabilities for their 
ADD diagna~e5 bssed on the recommended kappa 
criterion of .7P ('spitzer et al., 1967). Rubinstein and 
Brown (1984) failhd to meet this reliability criterion 
for both AJYDdH (.37) and ADD/WO (.50) sub- 
jects. Brown (1986) demonstrated adequate reliabil- 
ity for ADD/H (.73) using this criterion but not for 
ADD/WO diagnoses (.62). 
Regarding the use of a one-to-one observationin 
the clinic setting (i.e., subjects with a staff member) 
for the purpose of diagnosis, Ross and Ross (1982) 
and Denckla and Heilman (1979) have pointed out 
the variability in the behavior of ADD subjects. 
They have suggested that when in a one-to-one set- 
ting such as a clinic office, the ADD children's be- 
havior might be quite appropriate in marked con- 
trast to typical classroom behavior. Such findings 
argue against the appropriateness of the diagnostic 
rating procedures utilized in the Rubenstein and 
Brown (1984) and Brown (1986) studies. 
Several conclusions can be drawn regarding the 
operationalization of ADD subtypes. First, there is 
a lack of agreement regarding how to identify ADD 
subtypes. This observation is consistent with that of 
B. A. Shaywitz (1987). Second, many of the studies 
have utilized unidimensional ide~tification proce- 
dures, many of which have increased risk of yielding 
heterogeneous ADD groups. Third, as noted by 
Meents (1989), diagnosis is presently rating-scale 
driven. Use of such diagnostic procedures does not 
allow, however, for documentation of each ADD 
symptom through rating-scale usage. Fourth, many 
of the rating scales used wme standardized prior to 
the 1980 subtyping of ADD in DSM-III. This sug- 
gests the posisibility that these measures may have 
attention scales that also contain characteristics of 
hyperactivity, thus yielding hatterogeneaus ADD 
groups, Fifth, almost 20% of the reported studies 
used clinical jpdgment withoat acceptable levels of 
diagnostic reliability reported or without any reli- 
ability check (Barkley et al., 1990). Finally, it should 
be noted that there is one DSM-III critedon for 
ADD that has been ignored by all but 4 of the 21 
studies. DSM-III criteria require that ADD prob- 
lems have an age of onset by 7 ye@rs. Only Dykman 
et al. (1980), B r m (1986), and Bat'kley et al. (1990, 
1991) reported having included this additi~naj orite- 
rion in their research. 
Differentiation of ADD Subtypes 
The final methodological issue to consider is 
which behavioral measures have been employed to 
distinguish ADD/H and ADDlWO. The behav- 
ioral studies have utilized 37 different instruments in 
conjunction with DSM-III criteria to assess possi- 
ble differences between ADD/H and ADD/WO. 
These measures fall into the following categories: 
behavior rating scales, structured interviews, soci- 
ometric rathgs, self-report measures of self-concept 
and depression, intelligence measures, achievement 
tests, lanpage tests, perceptual-motor tests, mem- 
ory tests, tests of presumed innate and acquired au- 
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SUBTYPES OF ADD 
tomatic pracesses, measures of sustained attention, 
and tests of impulsivity. 
Among these, it can be concluded that the mea- 
sures that have differentiated the ADD subgroups 
successfully include behavior rating scales, sociom- 
etric ratings, self-report measures, math ability/ 
achievement measures, long-term memory mea- 
sures, and presumed measures of acquired 
automatic processes (Ackerman, Anhalt, Holcomb, 
& Dykman, 1986). In contrast to the conclusion of 
Carlson et al. (1986) "that the difference between the 
two groups may be more behavioral and emotional 
than c~ognitive" (p. 84), differences in both behav- 
ioral and cognitive areas are documented. 
Barkley et al. (1990) pointed out that some of the 
behaviloral diffe~rentiations are clouded by possible 
confounding of independent and dependent varia- 
bles in several studies that relied on teacher behav- 
ior-rating scales (Lahey et al., 1985, 1987). They 
acknowledge that this is also a partial problem (lim- 
ited to certain behavior ratings as dependent varia- 
bles) for their results. Partial confounding limited to 
behavilor ratings is also noted in Hynd, Lorys, et al. 
(1 99 1) 
Behavi~oral Distinctiveness of ADD/W and 
ADD/WO 
Con~sideration needs to be given to the distinctive 
clinical presentation of ADD/H and A D D N O 
children that has resulted from the behavioral stud- 
ies. Although caution has been urged in interpreting 
behavi~oral findings, a review reveals that though 
most behavioral distinctions were established origi- 
nally with experimentally classified subjects (Lahey 
et al., 1984, 1985) and averlapping samples, these 
behaviloral differences now have been confirmed 
using clinical subjects and independent samples 
(Barkley et al., 1990; Berry et al., 1985; Hynd, 
Lorys, et al., 1991; Lahey et al., 1987). Results of the 
behavioral studies then demonstrate possible differ- 
ences between the ADD/H and ADD/WO children 
in beha~vior, emotions, social interaction, academics, 
family background, and response to intervention. 
The resulting clinical profiles of the two groups 
are quite different. Considering the three primary 
features of ADD outlined in DSM-III, consistent 
with D'SM--III criteria for ADD/H, this group is 
empirically more active than the ADD/WO group 
but haa levells of inattentiveness similar to those for 
ADD/WO. Importantly, however, qualitative dif- 
ferences in inattention have been reported between 
the twcrl groups by Barkley et al. (1990). On the other 
hand, lincon~sistent with DSM-111 criteria, ADD/ 
WO children have been documented empirically to 
be less impulsive than ADD/H children (Berry et 
al., 1985; H[ynd, Lorys, et al., 1991; Lahey et al., 
1985, 1987, 1988; Maurer & Stewart, 1980) and not 
more impulsive than normal co~ntrols (King & 
Young, 1982). Findings, of Conte t:t al. (1985) and 
Barkley et al. (1990) dispute this c~onclusion by sug- 
gesting similar levels of impulsi~rity in the two 
groups. However, probliems with these two studies 
related to this particuliar point sl?ould be noted. 
First, Conte et al. (1985) is an butliex on three of the 
f ~ u r subject variables reviewed, having a smaller 
sample (8 subjects per group), higher percentage of 
girls, and among the oldest sudjects studied. Second, 
Barkley et al. (1990) reported l y i n g a high percent- 
age of overlapping diagnoses f oppositional defiant 
disordler among their AlDD d 0 group, which most 
likely influenced findings regarding impulsivity. It 
could be inferred, then, from dhese: findings that the 
UADD criteria of DSA4-IIIJ-R lmay be: more ap- 
propriate for identification of ADlD/WO because 
impulsivity is omitted from the di:tgnostic criteria. 
This conclusion is consistent wi1,h Lahey et al. 
(1988). 
Following some preliminary work with experi- 
mentally classified ADD saupbs, Lahey et al. 
(1985) suggested that A D D / ~ O rnay classify along 
the Internalizing dimension ofl behavior rather than 
the Externalizing dirnensiod as does ADD/H 
(Achenbach & Edelbrock, 198'3). It now appears on 
the basis of additional clinical(~ark1e~ et al., 1990) 
and factor-analytic data (Berrx et al., 1985; Lahey et 
d., 1988) that more credence slhoulti be given to this 
hypothesis. In this regardc B$rry let al. found evi- 
dence of separate ~ttentionalRCo~riitive ancl Atten- 
tionalJBehaviora1 factors on the Yale Children's In- 
ventory (S. E. Shaywitz, Schn$ll, B. A. Shaywitz, & 
Towle, 1986). Further, Lahe$ et id. (1988) found 
support for a Motor Hyperact vity/'lmpulsivity fac- i 
tor, an Inattention/Dinorgan$zatica factor, and a 
Sluggish Tempo factor on the SNAP. Tbe possibility 
that ADD/WO is a rpore ;ilctentional/cognitive/ 
anxiety type of disordta in yontnsst to the more 
attentional/behavioral/impul#vs aspects of 
ADD./H must be consitlered. In fa& Hynd, Lorys, 
et al. (1991) and Barkley et dl. (1990) have postu- 
lated that the two groups ma$ represent diqsimilar 
psychiatric disorders. 
In recent work, Barlkley eb al. (1990) described 
both ADD groups as nnderqchieving, having im- 
paired learning, and having qroblems with incom- 
plete work. It is possible, if nc/t likely, based on the 
present clinical profiles that qu litative differences in 
the two groups underpin simi 1 ar levelsof impaired 
school performance just as qualit,ative differences 
are documented in inattentiom As Hynd, Lorys, et 
al. (1991) suggested, poor school performance 
among ADD/H chi1dr1:n may be linked to atten- 
tionalhehavioral problems whereas it appears that 
poor school performance amon,g children with 
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A D D N O may be linked to more attentional/cog- 
nitive disabilities. This idea is supported by recent 
documentation of links between ADD/WO and 
learning disabilities (Hynd, Lorys, et al., 1991). 
To conclude, the review of behavioral research 
seems to suggest some significant behavioral differ- 
ences between ADD/H and ADD/WO. However, 
the serious clinical and methodological issues raised 
by this review, such as small total number of ADD/ 
WO children studied, widely varying operational 
definitions of ADD/WO, incomplete appraisal of 
DSM-111 criteria, presence of overlapping dis- 
orders, confounding of independent and dependent 
measures, and lack of controlled studies in some 
cases, necessitate considering these behavioral dif- 
ferences as tentative evidence of the empirical valid- 
ity of the ADD/WO classification. 
Although some evidence for cognitive differences 
between ADD/H and ADD/WO exists, few of 
these differences have emerged through the use of 
traditional psychometric data in these behavioral 
studies (Hynd & Willis, 1988). To investigate fur- 
ther the merit of distinct categories of attention def- 
icit disorders (American Psychiatric Association, 
1980, 1987), attempts have been made to distinguish 
ADD/H and ADD/WO on neurocognitive mea- 
sures. Neuropsychological studies may shed light on 
relatively unique neurocognitive patterns of abilities 
or deficits associated with subtypes of ADD. Fur- 
ther, results from these studies may suggest which 
neurological systems or structures may be impaired 
in ADD. 
Weuropsychological Studies of ADD 
Presently, there are 10 studies that have at- 
tempted to differentiate ADD/H from ADD/WO 
on the basis of neuropsychological measures; these 
are summarized in Table 3. At a conceptual level, 
these studies attempt to link disordered behavior to 
neurological/neuropsychological systems that may 
be dysfunctional. Because the focus of these studies 
is etiological, they are discussed separately from the 
more behavioral studies which should be considered 
more descriptive. This section addresses clinical 'and 
methodological issues associated with these neuro- 
psychological studies. 
Subject Characteristics 
Sample size. Neuropsychological studies have 
contrasted 256 ADD/H subjects with 177 ADD/ 
WO subjects, 125 clinic controls, and 97 normal 
controls. These total figures, however, are mislead- 
ing because 91 of the 93 subjects in Holcomb, Acker- 
man, and Dykman (1985) also participated as sub- 
jects in Holcomb, Ackerman, and Dykman (1986) 
as did 20 of the Hynd, Lory's et al. (1991) subjects 
in the Goodyear (1990) study. Further, of the re- 
maining subjects, all but 139 were evaluated through 
the same university clinic, so the possibility exists 
that subject populations overlapped, further reduc- 
ing the total number of subjects (Hynd et al., 1989; 
Schaughency, Lahey, Hynd, Stone, & Piacentini, 
1990; Stone, 1986). If there were maximal overlap of 
the samples in that clinic, then the total number of 
different subjects included in the neuropsychological 
studies would be reduced to 121 ADD/H subjects, 
88 ADD/WO subjects, 40 clinic controls, and 74 
normal controls, which are small numbers for draw- 
ing any firm conclusions about neuropsychological 
differences of ADD/H and ADD/WO children. 
Average sample size for these studies was 25.6 for 
ADD/H and 18.7 for ADD/WO, somewhat smaller 
than in the behavioral studies. 
Sex distribution. As with the behavioral stud- 
ies, the subject samples in the neuropsychological 
studies have been predominantly male (87% of the 
total reported sample). Both Holcomb et al. (1985, 
1986) studies as well as Sergeant and Scholten 
(1985) investigated only boys. On the other hand, 
the Hynd et al. (1989) study had a larger proportion 
of girls than the other neuropsychological studies. It 
is unknown how a higher proportion of girls might 
affect neuropsychological outcomes, but Berry et al. 
(1985) found behavioral differences among ADD 
subtypes related to sex. Trommer, Hoeppner, 
Lorber, and Armstrong (1 988) did not report the sex 
of their subjects. 
Chronological age. Ages of subjects participat- 
ing in the neuropsychological studies ranged from 
8.6 to 12.9 years. The average age was 9.5 years for 
children with ADD/H and 10.8 years for children 
with ADD/WO. ADD/WO subjects in the neuro- 
psychological studies were a year older on average 
than A D D m O subjects in behavioral studies (i.e., 
10.8 and 9.8 years, respectively). 
Psychometric data. Psychometric data were 
collected on all subjects in the neuropsychological 
studies with the exception of those investigated by 
Sergeant and Scholten (1985) and Trommer, Ho- 
eppner, Lorber, and Armstrong (1988). Mean 
WISC-R scores were as follows: VIQ, 103.7 for 
ADD/H and 101.5 for ADD/WO children; PIQ, 
102.0 for ADD/H and 99.5 for ADD/WO children; 
and FSIQ, 102.4 for ADD/H and 102,l for ADD/ 
WO children, Mean IQ scores from behavioral and 
neuropsychological resaarch are very consistent, ex- 
cept for VIQ for both ADD groups, which was 
higher in the neuropsychological studies. In none of 
these studies did the FSIQs of ADD/WO subjects 
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SUBTYPES OF ADD 
signific:antllr exceed those of ADD/H subjects. Con- 
sidering psjrchometric data available from both be- 
havior,al and neuropsychological studies, 10 of 12 
studies, show no differences in FSIQs for ADD/WO 
and ADD/H groups. Therefore, the Dykman et al. 
(1980) and Carlson et al. (1986) findings where 
FSIQ differences were documented (ADD/WO > 
ADD/'H) must be considered unusual. 
Metho~dological Issues 
Discussion now turns to methodological issues 
related to r~europsychological studies of ADDS. Is- 
sues related to experimental design, diagnostic crite- 
ria, and dependent measures are examined. Com- 
parisoins between neuropsychological and 
behavioral studies are presented. 
Experimental Design 
In contrast to the behavioral studies, all but two 
of the neuropsychological studies employed experi- 
mental designs comparing ADD/H, ADD/WO, 
and co~ntrol groups (Good year, 1990; Hynd, Lorys, 
et al., 1991). Most of the controlled studies used 
clinical subjects as controls (see Table 3 for a de- 
scription of these clinical controls). Three of the 
eight (Holcomb et al., 1985, 1986; Stone, 1986) stud- 
ies included both clinical and normal controls. 
Based on tliese findings, experimental design of the 
neuropsych~ological research appears adequate. 
Differential Diagnosis of ADD 
As seen in the review of behavioral studies, there 
are t w ~ ~ differential diagnostic issues to consider. For 
the nt:uropsychological studies both co-occurring 
diagnoses and operational criteria for defining 
ADDlH and ADD/WO groups are addressed. 
Co-occurring diagnoses. Similar to the findings 
with tlhe behavioral studies, the possibility that sub- 
jects have overlapping academic and/or behavioral 
problems exists in all but one of the neuropsycholog- 
ical studies, as most samples were drawn from re- 
ferred popidations. Reflecting their concern about 
this issue, Stone (1986); Hynd et al. (1989); and 
Hynd, Lorys, et al. (1991) provided more specific 
data albout co-occurring diagnoses of their subjects. 
Across these three studies, the higher percentage of 
phobias among their ADD/WO as compared to 
ADDl'H subjects might have been predicted be- 
cause lLahey et al. (1985) concluded on the basis of 
behavioral data that ADD/WO may be an internal- 
izing disorder.However, the co-occurrence of con- 
duct disorders in more than one third of the ADD/ 
WO subjects seems much higher than what would 
have been expected with an internalizing disorder. 
Such a finding casts doubt on the appropriateness of 
the operationalization of ADD/W(C) in these studies. 
This is a serious issue because the same operational 
criteria used by Hynd et al. (1989) were also em- 
ployed by Schaughency et al. (1990) and Stone 
(1986) and because no significant differences be- 
tween ADD/H and ADD/WO giroups were found 
in any of these studies. 
On the other hand, employing a different clinic 
sample Hynd, Lorys, et al. $1991) reported more 
predictable co-occurrinlg diaqnoses (Lahey et al., 
1985). Interestingly, 601% of lhe .PtDD/WO group 
had co-occurring deve11opmeqtalle:arning disorders 
whereas none of the AI)D/H Subj~ects did. It is rele- 
vant to note that significant repultr; were obtained in 
this study where co-occurring diagnoses were in the 
predicted direction. 
Operational criteria~. The second methodolo- 
gical issue to be addressed re ardirlg differential di- 
agnosis of ADD/H and KD /W(3 concerns what 4 operational criteria were used t o define the two sub- 
groups. Intellectual, medical, dnd behavioral criteria 
are considered. 
Exclusionary IQ criteria w$re included in the op- 
erational criteria of 8 of the 10 neuropsychological 
studies. Exclusion of subjects from these studies was 
based on criteria ranging fro9 IC! < 90 (Holcomb 
et al., 1985, 1986) to IQ < to 69 (Hynd et al., 
1989; Schaughency et <al., Stone, 1986). Ser- 
geant and Scholten (19851) did not utilize IQ - 
exclusionary criteria, reasone that they had a group 
with normal IQ because all s bjects were in regular 
education classes. This does ot, however, rule out 
icaps in their sample. 
I the possibility of mild cognitipe or behavioral hand- 
, 
Operational criteria regariing medication were 
provided in 3 of the 10 neuro sycliological studies. P 
Both Holcomb et al. (1985, 4986) studies required 
that subjects be free of mledicbtion at least 2 weeks 
prior to dependent measur . Holwever, status of 
medication during the dliagno 7 tic phase was omitted. 
In the remaining studie:~, no qepont on the status of 
medication was provided. 
Review of operational crit&ria For the behavioral 
definitions of ADD/H and A D/IiVO in the neuro- 
psychological studies reveal four different ap- t 
proaches to ADD subgroupiqg. First, as alluded to 
earlier, the Stone (1986); Schdughency et al. (1990); 
Hynd et al. (1989); and Lor s, Hlynd, and Lahey i. (1990) studies employed the same operational crite- 
ria. They utilized multidimenqional assessment pro- 
cedures which included inforbation from multiple 
sourcles across multiple situatibns. Group formation 
was based on interviews, obdervai.ions, and rating 
scales. To arrive at inldepenflent DSM-III diag- 
noses, the diagnosticiar~s reviawedl results of the in- 
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Table 3. Neuropsychological Studies of Children Diagnosed as Having ADD/H or ADD/ WO 
Neuropsychological 
Author($ N Differential Diagnosis Measures Results 
Holcomb et al. (1985) 93 males Operational Criteria: Visual ERPs were measured while subjects 1. WISC-R Controls > ADDS. 
ADD/H: n = 24 1. All subjects required to have FSIQ were engaged in RT task to a low-probabil- 2. No significant differences among the four 
ADD/WO: n = 21 > 90. ity nonsense trigram and either low-proba- groups in N2, Nc, or SW amplitude. 
RD: n = 24 2. All subjects free of stimulants for at bility symbols or 3-letter words. 3. P3 amplitude: Controls significantly > 
Normal controls: N = 24 least 2 weeks prior to ERP testing. 1. Amplitudes of ERP components N2, clinical groups. Trend: ADD/H > RD 
3. ADD/H criteria: P3, SW, Nc, and PC were measured. > ADD/WO. 
a. Raw score > 15 on teacher-rated 2. Latency of P3 component was mea- 4. Difference between target and nontarget 
Abbreviated Conners including sured. P3 amplitude: Controls > ADDS. 
adverse rating (2 or 3) on the three 5. Target P3 amplitude: Controls > ADD/ 
core motoric items. Mean rating WO. 
= 20.2. 6. Latency P' component to target and non- 
b. WRAT Reading and Spelling > target stimuli: Controls < ADDs. 
90. 7. Latency target P's in Block 2 compared 
c. Clinical rating of ADD/H by psy- to Block 1: ADD/H and ADD/WO > 
chiatric evaluation team. Controls. 
4. A D D 1 7 0 criteria: 8. P3 latency to unexpected stimuli: Con- 
a. Low ratings (1 or 0) on three core trols < ADDS. 
motoric items of Conners. Mean 
rating = 10.9. 
b. WRAT Reading and Spelling > 
90. 
c. Clinical rating of ADD/WO by 
psychiatric evaluation team using 
DSM-ZZZ criteria. 
5. RD and Control criteria: Rating < 
15 on Teacher Abbreviated Conners. 
Mean RD rating = 10.3; mean nor- 
Sergeant & Scholten 24 males 
(1985) ADD/H: n = 8 
ADD/WO: n = 8 
Normal controls: n = 8 
Holcomb et al. (1986) 91 males 
ADD/H: n = 23 
ADD/WO: n = 21 
mal-control rating = 2.4. 
Co-Occurring Diagnoses: 
All children attended "normal" school. 
Operational Criteria: 
All subjects received both observer and 
High-speed visual search task. 
teacher behavior ratings. Parent interviews. 
Developmental neurological examination. 
1. All ADD/H children significantly slower 
and less accurate than controls not due to 
slower performance in stages of encod- 
ing, search, and/or decision. Therefore, 
no deficit of selective attention, only 
slower cognitive processing. 
2. ADD/WO children significantly slower 
search rate than controls. This suggests 
possible selective-attention deficit. 
Operational Criteria: Auditory ERPs were measured while sub- 1. WISC-R: Controls > ADDS. 
1. All subjects required to have FSIQ jects were engaged in RT task to a low-prob- 2. RT of controls significantly faster than 
> 90. ability auditory stimulus. clinical groups. Clinical groups did not 
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RD: n = 24 
Normal controls: 
n = 23 
Stone (1986) 76 subjects 
ADD/H: n = 29 (86% male) 
A D D N O : n = 18 (89% male) 
Clinic controls: n = 19 (63% male) 
Normal controls: n = 10 (80% male) 
Trommer, Hoeppner, 76 subjects 
Lorber, & Armstrong ADD/H: n = 28 
(1988) A D D N O : n = 16 
Normal Controls: n = 32 
2. All subjects free of stimulant for at 
least 2 weeks prior to ERP testing. 
3. ADD/H criteria: 
a. Raw score > 15 on teacher-rated 
Abbreviated Conners including 
adverse rating (2 or 3) on the three 
core motoric items. Mean rating 
= 20.2. 
b. WRAT Reading and Spelling > 
90. 
c. Clinical rating of ADD/H by psy- 
chiatric evaluation team. 
4. ADD/WO criteria: 
a. Low ratings (1 or 0) on three core 
motoric items of Conners. Mean 
rating = 10.9. 
b. WRAT Reading and Spelling > 
90. 
c. Clinical rating of ADD/WO by 
psychiatric evaluation team using 
DSM-I11 criteria. 
5. RD and Control criteria: 
Rating < 15 on Teacher Ab- 
breviated Conners. Mean RD rating 
= 10.3; mean normal-control rating 
= 2.4. 
Co-Occurring Diagnoses: 
Referrals from mental health clinic, juvenile 
services, schools, and physicians. Exclusion 
of children with FSIQ < 65 or psychotic 
behavior. ADD/H: 66% co-occurring diag- 
noses. ADD/WO: 44% co-occurring diag- 
noses. 
Operational Criteria: 
Same as Schaughencv et ai. (1990). 
Cohen's kappas: kDb/Ei: .77 ADD/WO: 
.80 
~ o ~ ~ c c u r r i n ~ ~ i a ~ ~ o s e s : 
Both ADD groups heterogeneous for learn- 
ing disabilities judged based on special edu- 
cation or tutoring. Parent Interview on 
DSM-III criteria, Conners Parent Que3- 
tionnaire, No medication at time of testing. 
1. Amplitudes of ERP components N1, 
P2, N2, and P~~ were measured. 
2. Latency of P3b component was ex- 
amined. 
Children's Checking Task, a measure of sus- 
tained attention in which subjects listened to 
audiotape of numbers and had a five-page 
booklet with rows of numbers. Subjects 
crossed out numbersthat matched tape and 
circled errors. Errors of omission and com- 
mission were tabulated. 
- - - - 
~ u d i o t a ~ e d of go-no-go para- 
digm, 5 go signals (single tap); 5 nn-go sig- 
nals (two taps) in fixed random sequence at 
3-sec intervals. Child should raise and lower 
index finger to "go" srgnal, but ignore "no- 
go." 
dlffer significantly from one another. 
Trend: RD > ADD/H > A D D N O . 
3. P2 amplitude to unexpected stimuli: RD 
and ADD/H > ADD/WO and Con- 
trols. 
4. No significant dlfferences among the 4 
groups on N1, N2, and P3a amplitudes. 
5. Controls had greater ~3 bS on target trials 
than clinical groups. 
6. SW: Controls significantly > ADDS. 
7. PC: Control > R D and ADD/WO. 
No significant group differences for either 
omission or commission errors. 
1. c o n t r o l < ADD/H or ADD/WO in 
total errors 
2. A D D N O > Control or ADD/H in 
total errors and commission errors on 
first trial. 
3. ADD/WO greater improvement than 
ADD/H on second trial. 
(Continued) 
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Table 3. (Continued) 
Neuropsychological 
Author($ N Differential Diagnosis Measures Results 
Hynd et al. (1989) 81 subjects 
ADD/H: n = 43 (81% male) 
ADD/WO: n = 22 (77% male) 
Clinic controls: n = 16 (78% male) 
Goodyear (1990) 39 subjects 
ADD/H: n = 18 
A D D N O : n = 21 
Lorys et al. (1990) 100 subjects (79 male, 21 female; 87 Cauca- 
sian, 12 African-American, 1 Hispanic) 
ADD/H: n = 48 
A D D N O : n = 26 
Clinic control: n = 26 
Co-Occurring Diagnoses: 
Referred population. 
ADD/H: 56% conduct disordered, 9.3% 
phobias. 
ADD/WO: 36% conduct disordered, 27% 
phobias. 
Exclusion of Children With: 
1. FSIQ < 69. 
2. Neurological disorder. 
3. Psychotic disorder. 
Operational Criteria: 
1. Children's version of Schedule for 
Affective Disorders and Schizophre- 
nia (K-SADS) conducted in inter- 
view format with teacher, parent, 
and child. 
2. Rating scales were completed by 
parents and teachers. 
Same as Hynd et al. (1989). 
RT Measures: 
1. Simple RT to visual stimulus (i.e., 
light). 
2. Physical Match-Letter Pairs: RT to 
decide if two letters were physical 
match. 
3. Name Match-Letter Pairs: RT to 
decide if two letters were semanti- 
cally the same. 
4. Letter-String Match: RT to decide if 
two nonsense trigrams were the 
same. 
Boston Naming Test 
Woodcock Reading Mastery Test-Revised 
Co-Occurring Diagnoses: WISC-R: 
Both ADD groups contained children with 1. Verbal Comprehension. 
sole diagnoses of ADD/H and ADD/WO 2. Perceptual Organization. 
as well as children with conduct disorder as 3. Freedom From Distractibility. 
a secondary diagnosis. 4. Digit Span. 
- 
4. ADD/H > Control in errors on second 
t rU. 
5. ADD/H equally impulsive (number of 
commission errors) both trials. 
6. Greatest frequency of errors in youngest 
subjects. 
1. No significant differences between 
ADD/H and ADD/WO groups. 
2. ADD/H did not perform as well as Con- 
trol on letter-string match. 
1. ADD/WO nearly equal to ADD/H on 
Boston total scores; however, ADD/WO 
> ADD/H in number of cues needed. 
2. Word attack > word recognition for 
ADD/WO but not ADD/H. 
WISC-R: 
No significant results. 
LNNB-CR: 
1. Item 128: No significant differences. 
2. Item 65: No significant differences. 
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Exclusion of Children With: 
1. FSIQ < 70. 
2. Psychotic disorders. 
3. Neurological disorders. 
4. Conduct disorders excluded from 
clinic controls. 
Operational Criteria: 
Same as Schaughency et al. (1990). 
Schaughency et al. 55 subjects (predominantly male) Co-Occurring Diagnoses: 
(1990) ADD/H: n = 25 Referral sources were parents, physicians, 
ADD/WO: n = 14 schools, and state center for severe emo- 
Clinic controls: n = 16 tional and behavior disorder. 
Exclusion of Children With: 
1. FSIQ < 70. 
2. Psychotic behavior. 
3. Neurological disorder. 
4. Conduct disorders from clinic con- 
LNNB-CR: 
1. Memory scale: Item 128 (serial 
learning). 
2. Visual scale: Item 65 (visual-spatiai 
orientation). 
3. Rhythm scale: Items 41, 42. 
4. Motor scale: Items 16, 17. 
RT: 
Task required 3-letter string match. 
Sensory Localization: 
1. Left finger agnosia. 
2. Right finger agnosia. 
LNNB-CR 
3. Items 41, 42: ANCOVA with 
chronological age (CA) as only 
covariate. ADD/H and climc con- 
trol group differed @ < .U5). 
4. Items 16, 17: Post hoc comparisons 
between ADD/H and clinic control 
were significant (p < .036). 
Sensory Localization: 
Post hoc tests yielded significant results 
between ADD/H and ADD/WO. 
No significant differences on any of the clini- 
cal or special scales (i.e., Motor, Rhythm, 
Tactile, Visual, Receptive and Expressive 
Speech, Writing, Reading, Arithmetic, 
Memory, and Intelligence). 
trols. 
Operational Criteria: 
1. Children's version of Schedule for 
Affective Disorders and Schizophre- 
nia (K-SADS) conducted in inter- 
view format with teacher, parent, 
and child. 
2. Rating scales were completed by 
parents and teachers. 
Hynd, Lorys, et al. 20 subjects (predominantly Caucasian; Co-Occurring Diagnoses: Rapid Naming: Rapid Naming: 
(1991) lower-middle to middle-class SES; no psy- 1. ADD/H: 40% conduct disordered. 1. Color Naming (RAN). ADD/WO slower than ADD/H on RAN/ 
chiatric hospitalizations) 2. ADD/WO: 60% developmental 2. Color, Number, and Letter Naming RAS Combined Naming. 
ADD/H: n = 10 (9 male, 1 female) learning disorder. (RAS). 
ADD/WO: n = 10 (8 male, 2 female) Exclusions: 3. RAN/RAS Combined Naming. 
1. FSiQ < 70. 
4. Other neuro!ogica! disorder. 
Operational Criteria: 
1. WISGR: FSIQ > 70. 
2. K-SADS: parent and teacher. 
3. Parent and teacher behavior rating 
scales (Achenbach; SNAP). 
Note: ANCOVA = analysis of covariance; ERP = event-related potential; LNNB-CR = Luria-Nebraska Neuropsychological Battery-Children's Revision; RD = reading disabled; RT = reaction time; WRAT 
= Wide Range Achievement Test. 
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terviews and rating scales. Cohen's kappas were cal- 
culated to determine the reliability of these diagnos- 
tic procedures. These reliability measures ranged 
from .77 to .80 for both ADD/H and ADD/WO 
subjects. The studies of Sergeant and Scholten 
(1985) and Hynd, Lorys, et al. (1991) also employed 
similar multimodal identification procedures. 
This approach to ADD/H and ADD/WO identi- 
fication represents a vast improvement over the 
unidimensional assessment evident in most of the 
behavioral studies. The approach also has demon- 
strated adequate reliability (Spitzer et al., 1967). On 
the other hand, two difficulties with the approach 
are apparent. First, as mentioned previously, in the 
Hynd et al. (1989) study, these operational criteria 
resulted in one third of the A D D N O subjects hav- 
ing overlapping conduct disorders, which is con- 
trary to the typical behavioral profile for A D D N O . 
Second, no specific criteria for rating-scale usage 
were given in any of the studies. If, for example, the 
SNAP criteria from the Carlson et al. (1986) behav- 
ioral study were applied here, then hyperactivity 
indicators were permitted among ADD/WO sub- 
jects, which may account for some of the ADD/WO 
overlap with conduct disorders in Hynd et al. 
(1989). 
Another approach to ADD subtyping appears in 
the neuropsychological studies of Holcomb et al. 
(1985, 1986) and Trommer, Hoeppner, Lorber, and 
Armstrong (1988). Teacher ratings on the Ab- 
breviated Conners (Sprague et al., 1974) or Parent 
Conners rating scales and clinical rating by a psychi- 
atric evaluation team were used to classify ADD 
subgroups. Several problems are apparent with this 
approach. First, measurement is unidimensional. 
Second, there are several concerns about the Ab- 
breviated Conners Rating Scale (mentioned earlier). 
Holcomb et al. (1985, 1986),however, do attempt to 
address some of those concerns by specifying criteria 
with the Conners other than a total score. Third, 
measures of the reliability of the psychiatric evalua- 
tion team are not reported. 
Dependent Variables 
The final methodological issue related to the neu- 
ropsychological studies is what measures have been 
employed to differentiate ADD/H from ADD/WO 
children. Ten different measures have been used: 
visual and auditory event-related potentials (Hol- 
comb et al., 1985, 1986), the Luria-Nebraska Neu- 
ropsychological Battery-Children's Revision 
(LNNB-CR, Lorys et al., 1990; Schaughency et al., 
1990), sustained attention measures (Stone, 1986), 
reaction-time measures (Hynd et al., 1989), high- 
speed visual search tasks (Sergeant & Scholten, 
1985), rapid naming tasks (Hynd, Lorys, et al., 
296 
1991), an auditory go-no-go paradigm (Trommer, 
Hoeppner, Lorber, & Armstrong 1988), word re- 
trieval tasks (Goodyear, 1990), and a reading skill 
analysis (Goodyear, 1990). Some electrophysiologi- 
cal and neurocognitive differences have emerged. 
To summarize regarding methodological issues of 
neuropsychological studies, better experimental de- 
sign and use of multimodal assessment represent 
major improvements over the methodological prob- 
lems of behavioral studies. However, many of the 
other criticisms of methods in the behavioral studies 
apply to the neuropsychological studies as well. 
Inattention to status of medication must be consid- 
ered a serious issue when recording neurocognitive 
measures. Further concerns about co-occurring 
diagnoses have been raised. In addition, incomplete 
or impure measurement of DSM-III criteria con- 
tinue to be problems. Finally, the inconsistency of 
operational ddnitions, especially of ADD/WO, is 
problematic. 
Neuropsychological Differentiation of 
ADD/H and ADD/WO 
Next, consideration is given to the results of the 
neuropsychological attempts to distinguish 
ADD/H and ADD/WO. Additionally, differences 
between ADD/WO subjects and controls from this 
research are noted. 
Sixty percent of the neuropsychological studies 
have yielded significant differences between 
ADD/H and ADD/WO. Holcomb et al. (1986) 
found that ADD/H and ADD/WO subjects could 
be distinguished on the p 2 component of an auditory 
event-related potential. The amplitude of P 2 for 
ADD/H children was greater than for A D D N O 
children. The p 2 component is thought to measure 
the auditory nerve volley (Allison, 1984). For an 
auditory stimulus as in the Holcomb et al. (1986) 
study, the P component has a single fronto-central 
focus (Ritter, Kelso, Kutas, & Shiffrin, 1984) which 
was larger for ADD/H than for ADD/WO subjects 
in this study. 
Comparison to controls in the neuropsychologi- 
cal studies demonstrates that children with ADD/ 
WO, as well as children with ADD/H, have smaller 
than normal P 3 components in both auditory and 
visual modalities, and longer P3 latencies to both 
target and novel stimuli. P is thought to be closely 
related to attention, especially to the "relevance" of 
the eliciting stimulus (Picton, Donchin, Ford, 
Kahneman, & Norman, 1984). It is typically largest 
over the central (C,) and parietal (P,) areas. 
Neuropsychological distinctions among ADD 
subtypes were also found by Hynd, Lorys, et al. 
(1991). They found that ADD/WO children were 
slower than ADD/H children in responding to tasks 
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SUBTYPES OF ADD 
requiring them to name familiar alternating stimuli 
(e.g., colors, numbers, letters) as fast as possible. 
They interpreted these findings as consistent with a 
high rate of co-occurring learning disabilities, as 
learning-disabled children are thought to have defi- 
cits in automaticity (Hynd & Willis, 1988). This is 
also consistent with Ackerman, Anhalt, Holcomb, 
and Dlykrnan (1986) who hypothesized a lack of 
autoxnaticity of math facts for ADD/WO children 
based on latencies in solving math facts. Thase re- 
sults may also support previous behavioral findings 
by Lahey et al. (1985) of sluggish tempo among 
children with ADDJWO. Lorys et al. (1990) also 
found neurocognitive distinctions between ADD/ 
WO and ADD/H groups. They showed that ADD/ 
WO subjects demonstrate sensory-localization defi- 
cits, which are thought to be associated with parietal 
lobe functioning. Specifically, they found that per- 
formance on a finger agnosia task for the-left hand 
discriminated the ADD groups. 
Trommer, Hoeppner, Lorber, and Armstrong 
(1988) provided further support for cognitive dif- 
ferentiation of ADD/H and ADDJWO. They found 
significant differences between the ADD groups in 
error 11attems on a paradigm designed to evaluate 
the ability to emit a simple motor response to one 
stimulus and inhibit the response to a similar stimu- 
lus. ADD/WO subjects were initially more impul- 
sive than A.DD/H subjects and normals in the first 
trial bnt, unlike the ADD/H group, showed signifi- 
cant improvement in the second trial. ADDJH sub- 
jects were consistently impulsive in both trials. Sev- 
eral interpretations of these results are possible. 
First, ithis pattern of performance is consistent with 
the idea of a sustained attention disorder in ADD/H 
and a sielective attention disorder in ADDJWO. Sec- 
ond, PkDDJWO has beep linked consistently with 
anxiet:y in the behavioral studies through self-report 
and family history. It is possible that the initially 
impulsiive performance in the first trial is related to 
an initial nonfaciliatory level of performance anxiety 
which dissipates with continued performance. 
Oo~~dyear (1990) found further neurocognitive 
distinctions on word retrieval measures and on spe- 
cific rtmding skills. Interestingly, both groups had 
similar total scores on a word retrieval task but 
demonstvated qualitatively different performances. 
The A.DDtl,rWCJ group required significantly more 
word retrieval cues to achieve a performance similar 
to thalt of the A D D m group. Such a finding sug- 
gests s'ignifi~cant limitations for traditional psycho- 
metrics in distinguishing these groups. Additionally, 
children vvith ADDJWO, unlike those with 
ADD/%, slhowed an inconsistent pattern in the de- 
velopnient {of reading skills with word-attack skills 
exceeding word identification skills. 
Altlhough no ADD/H-ADD/WO differences 
emerged from Sergeant and Scholten's (1985) study, 
a distinction between ALDD/WO subjects and nor- 
mal controls was noted. Although this finding 
should receive cautious interprietation due to the fact 
that the ADD/WO group in this study was experi- 
mentally rather than clinically defined, ADD/WO 
subjects were slower than controls in the search 
stage of information processing. Sergeant and 
Scholten thought this findin4 was consistent with 
the presence of a selectivie attention deficit in this 
group, a hypothesis that has r&eive:d recent support 
from Barkley et al. (1990) Thle slo~wer rate of infor- 
mation processing may also be colnsistent with the 
Lahey et al. (1985) ancl Hynd Lorys, et al. (1991) 
results demonstrating sluggish cognitive tempo in 
ADD/WO children. 
Thus far, neuropsycbologi+al attempts to differ- 
entiate ADD/H from A.DD/YVO have yielded some 
early disappointing rewxlts but some recent encour- 
aging findings. Some possible reasons for this early 
lack of differentiation in th/e neiuropsychological 
studies may include the: follo$ing. First, it must be 
recognized that there are n$menous clinical and 
msthodological criticisms of the neiuropsychological 
studies. These problems- hich include small 
ADD/WO samples, ADD /IT 0 overlap with con- 
duct disorders, possibl~e incljsion of hyperactivity 
indicators in ADDJWlO ~defi ition~s, some inatten- 
tion to medication status, an utilization of cogni- I 
the dependent measures of limited complexity- 
may have contributed lo the tack of success in this 
research. Of particular1no1.e is limited task ciomplex- 
ity, which ranged from 11 tasks at the sim- 
plest lievel, to tasks of m 
mediate level, to rapid 1 
level, The low levels oft 
by recognition and mr 
sufficient to elicit ADID/H a/nd A,DD/WO differ- 
ences in neurocog~tive: procftsses. 
Second, Schaughency et al. (1990) suggested that 
the construct validity of the YNNB-CR may be an 
important issue in their lac4 of IIDDJH-ADD/ 
WO differential~ion. Factor a alysis of the LNNB- 
CR with learning-disabled s udelnts by Snow and 
Hynd (1985) indicated Ihe we 1 kest factor was a Sen- 
sory-Motor factor. Early behavioral results with 
ADD subtypes as well aa; fin 'ngs; by Lorys et al. P (1990) suggest that it wchuld be tlhis factor rather 
than Verbal-Intelligence or deneral Academic fac- 
tors (the two other factors of tve LINNB-CR) which 
might distinguish ADD/H fkom ADD,fWO chil- 
dren. Additionally, ScIiaugh$ncy et al. (1990) re- 
ported that although deficits on which ADD sub- 
types might be differentiated are consistent with 
dysfunctional frontal-lobe develc~pment, frontal- 
lobe tasks were eliminated &om the LNNB-CR 
battery based on the assumption lhat behaviors as- 
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SUBTYPES OF ADD 
If there are two distinct disorders sharing compo- 
nent(~) of attention in their clinical features, then 
how might the two be characterized? Douglas and 
Peters ((1979) described their view of ADD children 
diagnosed early as central nervous system ADDs 
who have impaired input processes. This is contra- 
dicted by Sagvolden and Archer (1989) and by Le- 
vine, C'ary, Crocker, and Gross (1983) who suggest 
ADD difficulties may be output problems. Levine et 
al. described children with developmental output 
failure who acquire input (especially reading skills) 
adequaiely but experience academic deterioration 
when demands for written output occur later in ele- 
mentary and middle school. It makes some concep- 
tual sense that ADD/H children who are identified 
somewhat earlier may have input difficulties possi- 
bly rel,ated to behavioral problems associated with 
activity level and/or impulsivity whereas ADD/ 
WO children who are identified somewhat later may 
manifest output difficulties related to neurocognitive 
procesrses associated with dysfunction of automa- 
tized isformation processing and slow cognitive 
speed. Such a conceptualization of A D D N O is as 
appeali~ng as it is parsimonious, allowing for the inte- 
gration of key neurocognitive deficits (i.e., long-term 
ret~iev,al of verbal information, lack of automaticity 
with number facts, slow writing speed, etc.) emerg- 
ing from this review. 
On the other hand, Douglas and Peters (1979) 
argued that disrupted input processes can have spi- 
raling effects due to the impact an metacognitive 
praces!ses. There is evidence to support such an oc- 
currence vvith ADD from Nussbaum, Grant, 
Roman, Paole, and Bigler (1990); however, the sig- 
nificance of their research findings is undermined by 
their f'ailure to subgroup ADDs. Such evidence 
would suggest, however, that output difficulties of 
ADD/WO children as described by Levine et al. 
(1983) may result from antecedent disturbances of 
selective attention. Research, especially linking 
these irnues with research in cognitive psychology, is 
needed1 to resolve some of these questions. 
Recently, research has revealed that diagnoses of 
leaxning disabilities frequently co-occur among 
ALID/'WO but not necessarily among ADDJH chil- 
dren (ldynd, Loqs, et al., 1991). This possible link 
between ADD/WO and lewning disabilities has 
previoilsly been suggested by Maurer and Stewart 
(1980),, over half of whose ADD/WO case reviews 
had co-o~curring learning disabilities, and by B. A. 
Shaywbt~ ( 1987), who reported that an estimated 
10% olf children with ADD are also learning dis- 
abled. The consistency of these recent findings with 
the coxwergence of the empirical results of behav- 
ioral and neuropsychological studies suggests that 
fertile research areas for the differential diagnosis of 
ADD/WO or WADD be in attentionalJcognitive 
and learning disabilities areas. It allso suggests, con- 
trary to the conclusion of Carlson let al. (1986), that 
ADD,IH and ADD/WC) differences are both behav- 
ioral and cognitive despite earlier difficulties in es- 
tablishing differences on traditiord psychometric 
measures (Hynd & Willis, 1988). 
The notion that learning disabilities frequently 
co-occur with ADD hats been incorporated1 in the 
most recent federal definition of learning disabilities 
(Wyngaarden, 1987). It may be that ADD/WO is 
the most frequent concurrent tp learning disabilities, 
not ADD/H. Future reseaxchneeds to address this 
issue as the preliminary stuqies dliscussed in this 
review suggest that children @th A.DDA3 rnay not 
do poorly in academic attainment, leven though their 
school performance may be variable. 
The relation between AD@/A.IDHD (or ADD 
subtypes) and learning di~~abilities is extremely im- 
portant (S. E. Shaywitz Pr. Bl A. Shaywitz, 1988; 
Silver, 1990; Wyngaarden, 19/87). IBoth the DSM- 
111 and DSM-111-R note tHe fre:quent co-occur- 
rence of ADD and ADHD, re~pecltilvely, with learn- 
ing problems but so far t he exapt incidence or nature 
of comorbidity has not been eptabhished. This issue 
is highlighted by the publica ion of recent studies 
(e.g., r4ugust & Garfinkel, 199 ) in which there is an 
unquestioning acceptance of 1 he JWM-III-R no- 
menclature. The failure to exaqhine: the nature of the 
symptoms that allow for a di~gnotsis of ADHD in 
relation to the co-occurrence o/f academic difficulties 
significantly diminishes tlhe dontmibution of these 
studies. 
Although the studies by ~ ~ n d , Lorys, et al. 
(199 1); Barkley et al. (1 990); dnd FdIaurer and Stew- 
art (1980) suggest a link bet+eer~ ADD/VV'O and 
learning disabilities, the qu~esti n remains as to what 
is the relation between ADD ! I3 and academic un- 
deracliievement? A recent study by Nieves, Connor, 
Hynd, Lahey, and Town (id press) directly ad- 
dresses this issue. Based on th literature suggesting 
that conduct disorder and A. 4 D/'l3 frequently co- 
occur and that children with cbnduct disorder suffer 
academic problems (Riltter, izar~d, & Whitmore, 
1970; Wilson & Herrnstein, 1 f 851, Nieves et al. (in 
press) examined undera~chieve@enit in children care- 
fully diagnosed as having oqly c:c)nduct disorder, 
children diagnosed as having eonduct disorder with 
co-occurring ADD/H, and ~hkldreim in a cluiic con- 
trol population. The findings 01 this study confirmed 
the fact that conduct disordkr is more often as- 
sociated with lower verbal IQ n d Ibat children with 
conduct disorder and ADD/$ tend to have lower 
academic achievement, particplarli~r in reading and 
spelling. 
The deficit in achievement, although statistically 
significantly below IQ, vvas just beyond the standard 
error of measurement (SE,) for IQ. This "deficit" 
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in academic attainment in conduct-disordered chil- 
dren with ADD/H would not be considered as ap- 
proximating the significant discrepancy between 
measured IQ and academic achievement normally 
required for a diagnosis of learning disabilities 
(Wyngaarden, 1987). Also, in the Nieves et al. (in 
press) study, socioeconomic status (SES) was sig- 
nificantly lower in the children diagnosed as having 
conduct disorder with co-occurring ADD/H. This 
finding is relevant because learning disabilities 
should not be diagnosed if the deficit in achievement 
is linked to SES factors (Wyngaarden, 1987). 
Thus, it could be concluded that underachieve- 
ment in ADD/H is related to the co-occurrence of 
lower verbal IQ in conduct disorder possibly linked 
to SES and is not characteristicof the considerably 
more significant delays in academic achievement 
evidenced by children diagnosed as having ADD/ 
WO. This tentative conclusion is supported by the 
finding of Hynd, Lorys, et al. (1991) that children 
with A D D R O , not ADD/H children, had au- 
tomatized linguistic deficits thought to characterize 
children with learning disabilities (Hynd 4 Semrud- 
Clikeman, 1989; Stanovich, 1986; Wolt Bally, & 
Morris, 1986). 
Other issues further cloud a more meaningful 
articulation of the relations among deficient aca- 
demic achievement, diagnosed learning disabilities, 
and ADD subtypes. For example, in both DSM-IiI 
and DW-IIJ-R, the diagnostic criteria for devel- 
opmental learning disorders have been criticized for 
their lack of clarity and failure to signify what con- 
stitutes a delay (Hoaper, Hynd, & Mattison, 1992). 
The DSM nomenclature is not in keeping with tradi- 
tional educational diagnostic practice as to the se- 
vere deficit in achievement (e.g., > 15 to 20 stan- 
dard score points) &at is typically required for a 
diagnosis of learning disabilities. 
Other important issues exist. For example, fac- 
tor-analytic studies suggest that attention deficit dis- 
order may be nanif~sted in two ways: (a) attention- 
cognitive (Berry et al., 1985) or 
inattention-disorganized (Lahey et al., 1988), and 
(b) attention-behavioral (Berry et al., 1985) or 
motar-impulsivity (Lahey et al., 1988). 
Although it is tempting to think that symptoms 
associated with ADD cluster into two broad factors, 
studies investigating the relation between conduct 
disorder and ADDkH suggest that three subgroups 
may exist: aggressive, h~peractive, and aggressive- 
hyperactive (Hinshaw, 1987; Szatmari, Boyle, & 
Offord, 1989'). Thus, behavioral symptoms as- 
soclatted with aggrtission and hyperactivity may be 
separable as might the symptoms associated with 
ADD and learning disability. Based on these find- 
ings w d the preceding discussion, it seems reason- 
able to ask if ADCI/H and ADD/WO are indeed 
subtypes of ADD or are they two separate syn- 
dromes sharing deficits in some components of at- 
tention? Barkley et al. (1990, 1991) suggest the latter 
because <f qualitatively different attentional styles 
found in the two groups. 
To date, only Barkley et al. (1990) have addressed 
this issue in the context of examining the kinds of 
behaviorally defined symptoms of inattention in 
children with ADD/H and those with ADD/WO 
who have been placed in learning disabilities class- 
rooms. As an example, it may well be that children 
with ADD/H have symptoms of inattention en- 
dorsed by parents or teachers that more closely re- 
flect impulsivity (e.g., frequent shifts from one un- 
completed activity to another) rather than those 
reflecting the kind of inattention symptoms one 
might expect from a ADD/WO child with co-occur- 
ring learning disabilities (e.g., often loses things nec- 
essary for tasks or activities at school or at home). 
The factor-analytic studies by Berry et al. (1985) and 
Lahey et al. (1988) suggest this issue is meaningful; 
findings in this regard may assist in addressing 
whether there are related subtypes or separate forms 
of childhoad psychopathology with different mani- 
festations of inattention. As Ingram (1990) sug- 
gested, there are many components to attention and 
deficits in various aspects of attentian may manifest 
differently in certain forms of childhood psychopa- 
thology. 
The neuropsychological studies, although few in 
number and characterized by methodological prob- 
lems, are important because they attempt to articu- 
late etiological, neurocognitive relations that the be- 
havioral-descriptive studies cannot address. It is 
clear, however, that studies conducted to date have, 
by and large, employed neuropsycho10~ical mea- 
sures of questionable validity or relevance (e.g., 
Hynd et al., 1989; Lorys et al., 1990; Schaughency 
et al., 1990; Sergeant & Scholten, 1985; Stone, 1986). 
Theoretically, many of these studies have been 
based on the literatwe suggmting thal; children with 
ADD/H have deficits in attention and motor regula- 
tion similar to patients with frontal-lobe lesions 
(Chelune, a erg us on, Koon, & Dickey, 1986; Drewe, 
1975; Mattes, 1980). Indeed, most neurobiological 
models of ADD/H implicate dysgnction in dience- 
phalic-fordbrain inhibitory systems (Ximetkin & 
Rapoport, 1986). Recent rolrjjrvndl aerebrd 1 Blood 
flow/co~~puted tomography (rCBP/GT) studies 
suppart this concoptpalirzation as the caudata-stria- 
tal region seems hypoactiva in ADDJH children 
when compwed to controls (Lou, Henrik'sen, & 
Bruhn, 1984; Lou, Manriks~b, Bruhn, Bomer, & 
Nielsen, 19891. Magqetic rewamce imaging; (MR.1) 
also has been employed to irsv~stigate dedaticrils in 
brain mlorphpllagy in ADD/H children; preliminary 
findings indiaata that the frontal lobes are character- 
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SUBTYPES OF ADD 
ized by symmetry as opposed to the normal pattern 
of right frontal width greater than left frontal width 
(Hynd,, Semrud-Clikeman, Lorys, Novey, & Eli- 
opulos, 1990). Variation in other subcortical struc- 
tures may also exist. Exploratory research has sug- 
gested that the genu and splenium of the corpus 
callosum may be smaller in ADD/H (and ADHD) 
children when compared to matched controls 
(Hynd,, Setnrud-Clikeman, et al., 1991). This varia- 
tion also may relate to the allocation of hemispheric 
attentional resources (Hynd, Sernrud-Clikeman, et 
al., 1991). 141~0, Hynd et al. (in press) using MRI 
have reported that chiidren with ADHD (all sub- 
jects miet criteria for ADD/H) have reversed asym- 
metry ~Qeft less than right) of the caudate nucleus, a 
subcortica1 structure with rich connections to the 
froptal lobes. This finding may be correlated with 
those c~f LOU et al. (1984, 1989). Consequently, evi- 
dence from a neurological perspective does suggest 
that anitmior dysfunction in structures involving at- 
tention~ and motor inhibition may be associated with 
ADD/H. Further, allocation of hemispheric atten- 
tional resources may be affected in ADDRI. 
Schiaughency and Hynd (1989) extended neuro- 
logical conceptualization in this regard to account 
for the behavioral symptomatology of ADD/WO. 
They proposed that the behaviors associated with 
ADD/WO seem more reflective of posterior, possi- 
bly right-hemispheric dysfunction. The sluggish 
cognitive tempo, frequently noted problems in 
achievement, particularly arithmetic, and possible 
visuospatial problems may reflect posterior dysfunc- 
tion. The studies by Schaughency et al. (1990); 
Lorys let al. (1990); and Hynd, Lorys, et al. (1991) 
examined these possible relations. Unfortunately, 
two of these studies employed tests or ~ s k s from the 
LNNB-CR which failed to find predicted deficits 
other than rthe fact that the ADD/WO children in 
Lorys et al. (1990) did show sensory-localization 
deficits compared to the ADD/H group. Concur- 
rent tal thme studies (Lorys et al., 1990; Schaug- 
hency et al., 19912), research accumulated indicating 
that the LNNB-CR was not particularly useful in 
clinical differentiation of children with significant 
psychopathology or developmental disorders 
(Hynd, 1988). Future studies should incoxporate 
develo~~mentally apprspriata task more sensitive to 
the neurobehavioral manifestations of ADD/H 
rather than employ clinical-psychometric measures 
of cognitive-perceptual processes thought to be cor- 
related to anterior or posterior dysfunction. 
For example, based on neurological evidence sug- 
gesting that the right hemisphere is important in 
mediatmg attention (Heilman & Van Den Abell, 
1980; Iteivicch, Alavi, & Gur, 1984), Voeller and 
Hleilman (1988a) examined children with ADHD on 
a letter and line cancellation tasks. Similar to pa- 
tients with known riglht-hemisph~eric lesions, the 
ADHD children evidenced more cancellation fail- 
ures onthe left side of tlhe page. It also appears that 
ADHD children evidence deficits in the ability to 
sustailn a simple motor act (motlor irnpersistence; 
Voeller & Heilman, 1980b), a deficit more frequently 
associated with right front$l lelsions in adults 
(Kertesz, Nicholson, & (Canceoiere:, 1985). Perform- 
ance on tasks more sensitive to disrupted neurologi- 
cal systems, such as those used by Yoeller and Heil- 
man (1988a, 1988b), may prcjve Inore meaningful, 
for example, than tests from the LINNB-GR in in- 
vestigating the notion that @vergent hemispheric 
systems may be differentially affected in A,DD/H 
and ALDD/WO (Schaughenc$ & Hynd, 1989). 
Conclusion 
Can it be concludecl that there: are two ADD 
subtypes? At present, our refiew does not permit 
such a categorical answer. The behavioral studies do 
provide good evidence in supgjort of the notion that 
at least two subtypes or two disorders may exist. 
However, as noted previously/ the total number of 
ADD,/WO subjects included ilp thes;e studies may be 
quite small thus calling into qkestion the reliability 
of the findings of these studieq. Also, the neuropsy- 
chological studies provide onlp limited support for 
clierentiating ADD/H and AT)D/WO. Signifi- 
cantly though, the instrament$ employed to investi- 
gate possible differences seem 10 cloud the interpre- 
tation of the studies that r e k t negative results 
(Hyncl et al., 1989; Lorys et a I., 1990; Schaughency 
et al., 1990; Stone, 1986). Fina \ ly, there may well be 
significant age-related elFects ob neuropsychological 
variables as suggested by ~ec)ter et al. (1987) and 
Passler et al. (1986) with regarfl to frontal-lobe mea- 
sures that obscure differential @erfo~rmance by ADD 
subtypes on other neuropsyc ological measures. 
Generally, however, this 1 r view provides more 
suppart for the diagnostic appdoaclh found in DSM- 
III (American Psychiatxic Mociation, 1 980) than 
that outlined in DSM-IJY- R (hmerican Psychiatric 
Association, 1987). In fact, the ondifferentiated list- 
ing of 14 possible symptorns 4 r PLDHD in DSM- 
111-R seems clearly at 7sarianGe with the decades of 
research emphasizing the pre omdnance of symp- 
toms associated with motor'ov ractivity. Four to 5 of ! 
the 14 symptoms listed emphaqize inattention (New- 
corn et al., 1989) whereas onlp 3 dlenote behaviors 
specifically considered reflective of hyperactivity (see 
Table 1). Consequently, 6 sy~dptmis in the DSM- 
III-R denote behaviors associpted with impulsivity 
which factor-analytic sttldies hbve clearly shown are 
split between two larger factoi-s co~mprising behav- 
isrs associated with eitller idttention or hyperac- 
tivity (Berry et al., 1985; Lahey et al., 1988). 
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Thus, although the research conducted to date 
does not permit us to state conclusively that there 
are two ADD subtypes or that there are two sepa- 
rate syndromes each sharing behaviorally defined 
deficits in attention, the research does provide more 
support for the diagnostic approach found in DSM- 
IIL In other words, there is more support for the 
differentiation of behavioral symptoms into those 
classified as inattentive or hyperactive than there is 
for a polythetic listing of behaviors cutting across all 
three domains (inattention, impulsivity, hyperac- 
tivity), any combination of which might result in a 
diagnosis. The polythetic approach results in a very 
heterogeneous group of subjects (August & Garfin- 
kel, 1990; Newcorn et al., 1989). 
Further behavioral studies are needed to address 
the many methodological problems characterizing 
the literature to date if a more theoretically and 
clinically meaningful differentiation of the ADD 
phenotype(s) is to be derived. As there appear to be 
significant family-genetic risk factors in ADD (Bied- 
erman, Faraone, Keenan, Knee, & Tsuang, 1990), 
the careful empirical validation of the DSM ap- 
proach should be a priority in research if the neuro- 
logical-genetic nature of this behaviorally diagnosed 
disorder is to be achieved. Likewise, more conceptu- 
ally sound neurological/neuropsychological studies 
are needed that tiit? dysfunctional process in children 
with ADD to deviatibns in brain metabolic pro- 
cessles or brain rnorphol~gy. Only in this fashion will 
data from the behavioral sciences significantly in- 
fluence the ability of researchers in the neuro- 
sciences ta articulate more fully the neurobiological 
basis and treatment d this common behavioral dis- 
order. 
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