Early Intensive Behavioral Intervention: Outcomes for Children With Autism and Their Parents After Two Years

Abstract

An intervention group (n=23) of preschool children with autism was identified on the basis of parent preference for early intensive behavioral intervention and a comparison group (n=21) identified as receiving treatment as usual. Prospective assessment was undertaken before treatment, after 1 year of treatment, and again after 2 years. Groups did not differ on assessments at baseline but after 2 years, robust differences favoring intensive behavioral intervention were observed on measures of intelligence, language, daily living skills, positive social behavior, and a statistical measure of best outcome for individual children. Measures of parental well-being, obtained at the same three time points, produced no evidence that behavioral intervention created increased problems for either mothers or fathers of children receiving it.

Full text

418 !American Association on Intellectual and Developmental Disabilities
VOLUME
112,
NUMBER
6: 418–438 !
NOVEMBER
2007
AMERICAN JOURNAL ON MENTAL RETARDATION
Early Intensive Behavioral Intervention: Outcomes
for Children With Autism and Their Parents After
Two Years
Bob Remington
University of Southampton, UK
Richard P. Hastings
University of Wales, Bangor, UK
Hanna Kovshoff and Francesca degli Espinosa
University of Southampton, UK
Erik Jahr
Akershus University Hospital, Norway
Tony Brown, Paula Alsford, Monika Lemaic, and Nicholas Ward
University of Southampton, UK
Abstract
An intervention group (n!23) of preschool children with autism was identified on the
basis of parent preference for early intensive behavioral intervention and a comparison
group (n!21) identified as receiving treatment as usual. Prospective assessment was un-
dertaken before treatment, after 1 year of treatment, and again after 2 years. Groups did
not differ on assessments at baseline but after 2 years, robust differences favoring intensive
behavioral intervention were observed on measures of intelligence, language, daily living
skills, positive social behavior, and a statistical measure of best outcome for individual
children. Measures of parental well-being, obtained at the same three time points, produced
no evidence that behavioral intervention created increased problems for either mothers or
fathers of children receiving it.
An increasing body of empirical research sug-
gests that early, intensive, structured intervention,
based on the principles of applied behavior anal-
ysis, is effective in remediating the intellectual,
linguistic, and adaptive deficits associated with au-
tism. Lovaas’s (1987) original archival study
showed that a group of children receiving 40
weekly hours of home-based early intensive be-
havioral intervention achieved significant gains in
IQ and social functioning in comparison with
control groups receiving either a less intensive in-
tervention or the standard treatment offered by
educational services. McEachin, Smith, and Lo-
vaas’s (1993) follow-up study showed that the
gains were maintained at age 11.5 years and that
8 of 9 children, previously identified as having
achieved ‘‘best outcome’’ status could not be dis-
tinguished from typically developing peers by as-
sessors blind to their treatment.
Since 1987, many researchers have conducted
evaluation studies attesting to the effectiveness of
early intervention with autism, but most have suf-
fered from methodological limitations that threat-
ened their internal validity. For example, in com-
mon with Lovaas (1987), several subsequent stud-
ies were not truly prospective randomized control

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trials because the researchers were unable to assign
children to groups randomly (e.g., Anderson, Av-
ery, DiPietro, Edwards, & Christian, 1987; Birn-
brauer & Leach, 1993; Eikeseth, Smith, Jahr, &
Eldevik, 2002) or used archival data to form a
comparison group (Sheinkopf & Siegel, 1998).
Others still relied on simple pre–post group com-
parisons (e.g., Stahmer & Ingersoll, 2004; Weiss,
1999) or controlled single-case studies (e.g.,
Green, Brennan, & Fein, 2002).
In summary, there are few randomized con-
trol trials that meet adequate internal validity cri-
teria and demonstrate the efficacy of early inten-
sive behavioral intervention. Two exceptional
studies (Sallows & Graupner, 2005; Smith, Groen,
& Wynn; 2000) compared the effects of early in-
tervention implemented using either a clinic- or a
parent-directed model. Smith et al. (2000) showed
that clinic-based intervention lasting 25 hours per
week for 2 to 3 years had greater impact than a
less intensive parent training-based intervention (5
hours per week). Group measures of children’s in-
telligence, visual–spatial skills, and language did
not differ at age 3 years, but changes in favor of
the clinic-directed group were apparent at age 7
to 8 years. In contrast, Sallows and Graupner
(2005) found no differences between clinic- and
parent-directed programs on similar measures after
4 years of treatment. In this study, however, be-
tween-group differences in the intensity of inter-
vention were much less marked.
The paucity of randomized control trials in
this area reflects the considerable difficulties of
staging them: Unlike drug trials, where patients
are, in principle, blind to the intervention, parents
are made well-aware in advance of the treatment
their children will receive. Moreover, as knowl-
edge accumulates and early intervention is ac-
cepted as a treatment of choice for autism (e.g.,
Surgeon-General, 1999), researchers face ethical
difficulties with random assignment, and families
become less willing to commit their children to
long-lasting treatments of dubious utility. Thus,
although a randomized controlled trial approach
can, under idealized conditions, produce the
strongest evidence establishing the efficacy of an
intervention (see, e.g., Whitehurst, 2003), it may
be difficult to conduct further evaluative trials of
early intensive behavioral intervention unless well-
matched, equally credible alternatives can be
pitted against standard procedures.
In any case, it is likely that the effectiveness
in practice of early intensive behavioral interven-
tion would be overestimated by any putative ran-
domized trial. In general, the external validity of
such trials is compromised by tight control of var-
iables, including co-morbidity, treatment fidelity,
treatment adherence, and self-selection into and
out of trials (Kendall, Chu, Gifford, Hayes, &
Nauta, 1998; Persons & Silberschatz, 1998; Selig-
man, 1995). Absence of control of such factors is
commonplace in typical service settings so the
long-term clinical benefit of any intervention de-
pends on its remaining effective in conditions that
are less than optimal. Considerations of this kind
have given rise to field effectiveness research, in
which random assignment to groups and the most
rigorous experimental control are traded against a
more naturalistic evaluation of service delivery in
context. Two recent evaluations of early behav-
ioral intervention for autism (H. Cohen, Amerine-
Dickens, & Smith, 2006; Howard, Sparkman, Co-
hen, Green, & Stanislaw, 2005) have adopted this
approach.
Using the Diagnostic and Statistical Manual of
Mental Disorders (DSM-IV ) (American Psychiatric
Association, 1994) criteria rather than the ‘‘gold
standard’’ research tool, namely, the Autism Di-
agnostic Interview-Revised (Lord, Rutter, & Le
Couteur, 1994), Howard et al. (2005) identified 61
children who met criterion either for autistic dis-
order or for pervasive developmental disorder–not
otherwise specified (PDD-NOS). They compared
29 children who received intensive clinic-directed
behavior analytic intervention (25 to 40 hours per
week) with two comparison groups, one (n!16)
that received equally intensive eclectic interven-
tion and the other (n!16) whose members were
not enrolled in any intensive public intervention
programs. Assignment to groups was not random-
ized but depended on the advice of practitioners,
with ‘‘parental preferences weighted heavily’’
(Lord et al., 1994, p. 364). Unusually, Howard et
al. eschewed direct group comparison using AN-
OVA models, opting instead for a multiple re-
gression-based analysis, with group membership
treated as a categorical variable. This showed that
prior to treatment there were no differences be-
tween the behavior analytic intervention group
and the two comparison groups combined.
In a second analysis of functioning 14
months later, Howard et al. (2005) found that
children in the intensive behavior analytic inter-
vention group had higher scores than those in the
combined comparison groups on standardized
tests of cognitive, linguistic, and adaptive func-

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tioning. Although the effects implied by these
analyses were confirmed in a similar test of the
absolute change scores on all measures, no anal-
ysis taking into account conditional change (i.e.,
relative to baseline scores) was presented.
In a 3-year prospective outcome study carried
out in a community setting, Cohen et al. (2006)
compared 21 children receiving early intensive be-
havioral treatment with an equal number of chil-
dren participating in public school special educa-
tion classes. Random assignment to groups was
not attempted; instead, assignment was based on
parental preference and a file review process used
to identify an IQ- and CA-matched child for each
child receiving intensive intervention. In this way,
it was possible to form a group of children ‘‘who
met participation criteria . . . and whose parents
chose other services’’ (p. S147). Both groups in-
cluded some children with a diagnosis of autism
and others with a PDD-NOS diagnosis, but the
proportion of the latter was lower in the interven-
tion group. Analysis of covariance (ANCOVA),
using baseline scores as the covariates, and com-
paring performance after 1, 2, and 3 years revealed
that the intensive group was superior on measures
of IQ and adaptive behavior, but not on measures
of language or nonverbal skills. Moreover, the ab-
sence of a Group "Time interaction indicated
that between-group performance differences
achieved after 12 months did not increase
throughout the treatment. The number of chil-
dren scoring in the normal range on the primary
outcome measure (IQ) was higher in the intensive
intervention group after 3 years, but this differ-
ence was not statistically significant.
Results of the Howard et al. (2005) and H.
Cohen et al. (2006) studies suggest that early in-
tensive behavioral intervention can be effective
when delivered in more typical community set-
tings and when compared with treatment as usual
the typical mix of interventions available to chil-
dren with autism. However, in common with al-
most all research in this area, these researchers did
not consider two crucial questions that we sought
to address in the present research. First, does early
intensive behavioral intervention have an impact
beyond the cognitive, language, and adaptive be-
havior deficits associated with autism, additionally
affecting the characteristic diagnostic symptoms
of the disorder? In the present study, we included
rating scale measures of autistic presentation, be-
havior problems, and prosocial behavior, as well
as an observational measure of joint attention
(Mundy & Crowson, 1997). The second issue we
addressed concerns the impact of intensive inter-
vention on family members. This has been ex-
plored only minimally, and although existing data
suggest that the mothers and siblings of partici-
pating children are not adversely affected (Birn-
brauer & Leach, 1993; Hastings, 2003a; Hastings
& Johnson, 2001; Smith, Buch, & Gamby, 2000;
Smith, Groen, & Wynn, 2000), there is as yet no
published controlled study of a range of measures
of both maternal and paternal well-being.
We also explored a key methodological issue
relating to intervention effectiveness by adopting
a more precise approach to identifying ‘‘best out-
come’’ children based on Jacobson and Truax’s
(1991) objective criteria for establishing whether a
particular child has benefited meaningfully from
an intervention. These criteria are (a) reliable change
(the extent to which statistical factors can be ruled
out as an explanation for apparent change) and
(b) clinically significant change (the extent to which
change is also clinically meaningful). Although in
earlier research investigators have used a criterion
of IQs moving to within the normal range (Birn-
brauer & Leach, 1993; Eikeseth et al., 2002; Lo-
vaas, 1987; McEachin et al., 1993; Sallows &
Graupner, 2005; Smith et al., 2000), to the best
of our knowledge this is the first study simulta-
neously to apply statistical criteria for both reli-
able and clinical change to the outcomes for early
intensive behavioral intervention programs.
We explored these three key issues within the
United Kingdom educational system, where in
previously published research, based on an un-
controlled survey of the impact of home pro-
grams, Bibby, Eikeseth, Martin, Mudford, and
Reeves (2001) reported only minimal outcomes
and wide variations in the quality and intensity of
service delivery. In contrast, we sought to con-
struct the most rigorously controlled field effec-
tiveness study achievable within the constraints of
the prevailing culture. This involved a prospective
2-year longitudinal design, comparing children
with autism whose families had chosen intensive
behavioral intervention from a range of different
service providers in England with children whose
parents were not seeking this type of intervention
and were receiving typical statutory services (treat-
ment as usual).
In summary, we designed this study as a rig-
orous test of whether early intensive behavioral
intervention for children with autism can be ben-
eficial in routine use, incorporating a wide range

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of outcome measures for both children with au-
tism and their parents. We used objective criteria
to identify children achieving ‘‘best outcome.’’
Following previous effectiveness studies, we ex-
pected intervention to lead to improvements in
children’s cognitive, language, and social func-
tioning when compared with treatment as usual.
Existing family research suggests that parents’ psy-
chological well-being would not be adversely af-
fected by engagement with intensive intervention,
although it was unclear whether positive out-
comes could be expected. Given the lack of pub-
lished data, we had no expectations as to whether
there would be positive changes in ratings of au-
tistic symptoms, behavior problems, or measures
of joint attention behaviors following early inten-
sive behavioral intervention.
Method
Design Overview
Two groups of preschool children with a for-
mal diagnosis of autism were identified. Parents of
children in the intervention group had opted for
early intensive behavioral intervention, either pro-
vided from public funds or purchased privately;
parents of children in the comparison group were
not actively seeking behavioral intervention, and
instead were receiving publicly funded standard
provision offered by their Local Education Au-
thority (i.e., treatment as usual). Assessments of
the children’s cognitive functioning, adaptive be-
havior, autistic behaviors, and social and com-
municative skills were undertaken at three data-
collection points: prior to intervention (baseline);
after 1 year, and again after 2 years of intervention
(12- and 24-month assessments). Measures of pa-
rental mental health, stress, and positive percep-
tions of their child were obtained at the same time
points.
Participants
Children with autism. Children were recruited
through referrals from local education authorities,
through advertisements placed with the United
Kingdom National Autistic Society, its regional
branches, and through parent groups or charities.
Demographic data relating to families appear in
Table 1 and to children, in Table 2 (for baseline
information, see Results). To meet the inclusion
requirements for this study, all children in both
the intervention and comparison groups had to
meet the following criteria. First, we required a
diagnosis of autism based on the Autism Diag-
nostic Interview-Revised carried out by an assessor
(the last author), who was fully trained to admin-
ister and score this instrument for research pur-
poses. All children had also either previously been
diagnosed with autism by a clinician independent
of the research program or had a suspected diag-
nosis of autism. Second, children were required to
be between 30 and 42 months of age at time of
their induction. Third, they were required to be
free of any other chronic or serious medical con-
dition that might interfere with the ability to de-
liver consistent intervention or might otherwise
adversely affect development. Finally, all the chil-
dren lived in the family home.
We identified 44 children who met these cri-
teria. The families of 23 of them, constituting the
intervention group, had opted for early intensive
behavioral intervention, either receiving provision
from the University of Southampton and funded
through their local education service (n!13) or
through a private service provider (n!10). In the
latter cases, services were either paid for by the
parents themselves or by their local education ser-
vice. The remaining 21 families, the comparison
group, were receiving various forms of publicly
funded educational provision for their children.
The groups differed slightly on chronological age
(CA), with the comparison group children (M!
38.4 months, SD !4.4) being on average approx-
imately 3 months older than the children in the
intervention group (M!35.7 months, SD !4.0),
t(42) !2.14, p#.05. None of the other demo-
graphic variables assessed for the children differed
between the two groups at baseline assessment.
Chronological age was explored as a control var-
iable in the main statistical analyses.
Parents. Forty-four mothers and 31 fathers of
children in the intervention and comparison
groups provided data on some aspects of the
child’s functioning and on their own well-being.
Their demographic details are shown in Table 1.
In the sample as a whole, there were 40 couples
at the baseline assessment. Nine families had a
father at home who declined to participate
throughout the research. For 4 families, the father
was not living in the same home as the mother
and the child with autism at baseline; these fathers
did not participate throughout the research. The
two groups were very similar on the majority of
parent/family demographic characteristics. Al-
though some demographic differences appear to

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Table 1. Demographic Characteristics of Families by Group
Demographic
Intervention (n!23)
n/
Mean %/SD Range
Comparison (n!21)
n/
Mean %/SD Range
Families
Marital status
Married 16 69.6 16 76.2
Living with partner 4 17.4 4 19
Divorced/Separated/Single and
not living with partner 3 13 1 4.8
Siblings
0 5 21.7 3 14.3
1 11 47.8 13 61.9
2 7 30.4 4 19
3 0 0 1 4.8
Siblings with developmental disabilities
0 20 87 13 61.9
1 2 13 7 33.3
2 0 0 1 4.8
All mothers (n!44) 23 21
Mean age 35.7 4.0 26–42 33.6 3.8 26–41
Level of education
No university education 13 57 17 81
University education 10 43 4 19
Paid work 7 30.4 7 33.3
Full-time 0 0 0 0
Part-time 7 100 7 100
All fathers living in the family home (n!40) 20 20
Mean age 38.8 5.5 31–50 37.1 4.8 30–53
Level of education
No university education 10 50 11 55
University education 10 50 9 45
Paid work 19 95 18 90
Full-time 19 100 17 94.4
Part-time 0 0 1 5.6
Fathers who responded to questionnaires (n!31) 16 15
Mean age 38.7 4.8 31–50 37.5 5.4 30–53
Level of education
No university education 7 44 8 53
University education 9 56 7 47
Paid work 15 93.8 13 86.7
Full-time 15 100 12 92.3
Part-time 0 0 1 7.7
Note. All mothers responded to the questionnaires but only 31 fathers responded similarly. Data for both subsamples
appear in the table.

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Table 2. Unadjusted Means (SDs) of Child Measures by Group and Assessment Point
Measure
Baseline
Intervention Comparison
12-month assessment
Intervention Comparison
24-month assessment
Intervention Comparison
IQ** 61.43 (16.43) 62.33 (16.64) 68.78 (20.49) 58.90 (20.45) 73.48 (27.28) 60.14 (27.76)
MA
a
** 22.04 (6.89) 23.71 (6.00) 33.70 (10.16) 29.81 (9.89) 44.39 (16.39) 38.00 (17.44)
VABS
b
Composite 114.78 (26.89) 113.57 (29.78) 169.70 (49.07) 145.76 (45.56) 202.83 (61.98) 182.86 (58.89)
Communica-
tion 23.52 (11.35) 21.62 (10.81) 42.83 (18.25) 34.62 (17.17) 54.74 (24.43) 46.00 (24.51)
Daily Living* 24.13 (7.49) 25.43 (10.56) 39.52 (14.71) 35.52 (14.34) 50.22 (16.46) 44.67 (16.99)
Socialization 29.57 (6.65) 28.29 (7.48) 38.52 (12.57) 33.14 (11.77) 43.52 (15.94) 41.48 (14.52)
Motor Skills* 37.57 (6.37) 38.24 (7.06) 48.83 (6.84) 44.48 (7.70) 54.35 (9.12) 50.71 (8.21)
Joint attention
c
Initiating 3.33 (4.40) 3.63 (4.92) 7.71 (7.52) 6.19 (8.79) 11.76 (9.41) 11.19 (13.86)
Responding* 5.29 (3.62) 5.94 (3.91) 8.95 (4.18) 7.13 (5.21) 11.29 (3.47) 10.06 (4.99)
a
Mental age.
b
Vineland Adaptive Behavior Scales Raw Scores.
c
Measured using the Early Social Communication Scales.
*p#.05. **p#.01 on main effects for combined 12- and 24-month data. Intervention group n!23 and comparison
group n!21, except for joint attention, intervention group n!21; comparison group n!16.
be present, no differences between the groups
were large enough to reach statistical significance
at the .05 level. Thus, none of these characteristics
were considered as candidate control variables in
the following analyses.
Child Measures
We used norm-referenced instruments to
gather the cognitive, language, and behavioral
outcome data for the children. The assessments
were chosen for their good psychometric proper-
ties and use in published outcome studies with
similar populations. An important consideration
was their potential utility for testing children with
autism. Many tests require language skills and sus-
tained attention, two abilities that may also be
affected in such children, whose symptomatic def-
icits in language, intellectual, neurological, adap-
tive behavior, and interpersonal skills could influ-
ence performance on standardized measures and
thus impact on the reliability and validity of any
test. All tests were administered according to the
standard procedures to ensure our data were com-
parable with those from other studies. Although
in some cases this could potentially have led to
an underestimate of children’s ability (e.g., chil-
dren reaching a ceiling on the Bayley Scales may
have continued to score on the nonverbal, non-
social items had these been administered), scoring
methods did not differentially favor either group.
The tests selected were administered by a mas-
ter’s level trained psychometrician (the third au-
thor), who had over 4 years of experience with
children who have autism and who exercised ev-
ery caution to obtain reliable and valid data. Al-
though resources did not allow for formal inde-
pendent reliability checks when assessments by in-
dependent psychometricians were available, these
scores were always within a standard error of mea-
surement of those reported below. Moreover, the
third author was not informed of group status,
worked independently of intervention teams, had
no access to intervention reports, and her contact
with the family was limited to the annual assess-
ments.
Intellectual functioning. The Bayley Scales and
the Stanford Binet Intelligence Scale: Fourth Edi-
tion (Thorndike, Hagen, & Sattler, 1986) were
both chosen, in part, for their low floor. The Bay-
ley, designed for children up to 42 months of age,
is appropriate for children with intellectual dis-
abilities or those whose language skills are not suf-
ficiently advanced to take a full-scale intelligence
test. If children received the Bayley scales at a CA
that exceeded the norms of the test, a mental age
(MA) was calculated based on their raw score us-
ing Table B.2 in the Bayley manual. A ratio IQ
was then computed based on the MA/CA "100
formula. The Stanford-Binet provides normative
data from the age of 2 years and, with only one

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timed subtest, provides a good deal of flexibility
when assessing children with autism.
Language. The Reynell Developmental Lan-
guage Scales–Third Edition (Edwards et al., 1997)
was chosen primarily because it is one of the few
language assessments previously used in early in-
tensive behavioral intervention outcome studies
and provides separate measures of expressive lan-
guage and comprehension. However, the updated
United Kingdom normed version used provides
normative data only from 21 months of age, sig-
nificantly older than the norms in the 1985 ver-
sion, which begin at 12 months.
Adaptive skills. The Vineland Adaptive Behav-
ior Scale–Survey Form (Sparrow, Balla, & Cic-
chetti, 1984) was chosen based on its prolific use
and the fact that it could be administered in a
short version (the survey form). The Vineland as-
sesses adaptive behavior across four domains: So-
cialization, Communication, Daily Living Skills,
and Motor Skills. Unfortunately, improvements
in the adaptive behavior of children with autism
are not always reflected in Vineland standardized
scores. This is in part because higher functioning
children show uneven developmental profiles
with interdomain scatter (Burack & Volkmar,
1992) and in part because low-functioning chil-
dren may show little scatter, owing to basal effects
(Carter et al., 1998). To avoid such problems in
research (as opposed to diagnostic) applications
with children who have autism, Carter et al.
(1998) recommended that raw scores be used in
preference to standardized scores.
Rating scales for child behavior. The Positive So-
cial subscale of the Nisonger Child Behavior Rat-
ing Form (Tasse´, Aman, Hammer, & Rojahn,
1996) and the parent report version of the Devel-
opmental Behavior Checklist (Einfeld & Tonge,
1995) were chosen to assess child behavior. The
Nisonger is an informant behavior rating scale de-
signed to assess children with intellectual disabil-
ities. The Developmental Behavior Checklist is a
behavior rating questionnaire yielding a Total Be-
havior Score, indexing the severity of behavior
problems and offering a subset of items that func-
tion as a reliable and valid autism screening tool
(the Developmental Behavior Checklist-Autism
Screening Algorithm, Einfeld & Tonge, 2002).
The Autism Screening Questionnaire (Berument,
Rutter, Lord, Pickles, & Bailey, 1999) was also
used. Derived from the Autism Diagnostic Inter-
view algorithm (Lord et al., 1994) and completed
by parents, this instrument provides a dimension-
al score for the symptoms of autism that was used
in the analyses.
Observational measures of nonverbal social com-
munication. The Early Social Communication
Scales (Mundy, Hogan, & Dohering, 1996) is a
videotaped semi-structured observational instru-
ment in which the tester presents a standard set
of toys in ways designed to elicit social and com-
municative behaviors in an ecologically valid con-
text. The key variables obtained through admin-
istration of the scales were measures of initiating
and responding to joint attention. Initiating joint
attention refers to the frequency with which chil-
dren use eye contact, pointing, and showing to
share the experience of a toy or object during test-
ing. Responding to joint attention refers to the num-
ber of times, over eight trials, in which a child
correctly turned his or her eye gaze and aligned
attention in the direction of the tester’s distal
point to a poster. Children with autism are less
likely than typically developing children, or chil-
dren with intellectual disabilities, to initiate or re-
spond to joint attention (McEvoy, Rogers, & Pen-
nington, 1993; Mundy & Crowson, 1997; Mun-
dy, Sigman, Ungerer, & Sherman, 1986). There-
fore, in the present study we assessed whether
these social interaction behaviors would improve
differentially for the intervention group as a result
of participating in a program requiring many
hours of one-to-one interaction with adults.
Interrater reliability was assessed using video-
taped data from 25% of children (9) at each time
point, scored by an independent rater blind to
group status and trained to reliability level on Ear-
ly Social Communication Scale training video-
tapes. Intraclass correlations between the paired
ratings, used to assess consistency between raters’
codes at all three assessment points, ranged from
.95 to .99 for initiating joint attention and .96 to
.97 for responding to joint attention.
Self-Report Measures of Parental Well-Being
The Hospital Anxiety and Depression Scale
(Zigmond & Snaith, 1983), chosen as a measure
of parents’ mental health, includes two subscales,
one assessing depression and the other, anxiety.
Previous research with parents of children with au-
tism has shown that the measure maintains good
reliability (internal consistency) for both mothers
and fathers of children with autism (Hastings,
2003b; Hastings & Brown, 2002). The Parent and
Family Problems subscale of the Questionnaire on
Resources and Stress–Friedrich short form (Fried-

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rich, Greenberg, & Crnic, 1983) was chosen as a
general measure of parental stress. This scale
yields a total stress score after five items previously
shown to constitute a robust measure of depres-
sion in parents of children with disabilities (Glid-
den & Floyd, 1997) have been removed from the
scale. This modification ensured that there was no
overlap between the measures of stress and of
mental health. The resulting 15-item scale had
strong internal consistency in the present sample
(Kuder-Richardson coefficients were .87 for moth-
ers and .83 for fathers at baseline). The Kansas
Inventory of Parental Perceptions Positive Contri-
butions subscale (Behr, Murphy, & Summers,
1992) was chosen as a measure of the degree to
which parents hold positive perceptions of their
child and the child’s impact on the family (e.g.,
bringing the family closer together, helping other
family members to become more understanding
of other people, and being a source of happiness
and fulfillment). In the present research, we used
the total positive perceptions score. This score had
a high level of internal consistency for both moth-
ers, Cronbach’s $!.95, and fathers, $!.95.
Procedure
Intervention group. All children in the interven-
tion group received home-based early intensive
behavioral intervention for 2 years. Trained tutors
and parents delivered one-to-one teaching based
on applied behavior analysis for 25.6 hrs per week
on average (SD !4.8, range !18.4 to 34.0). Thir-
teen of the 21 programs were provided by the
University of Southampton and were free at the
point of use for the parents nominated by the
local education authority that funded the Univer-
sity intervention team (which included the fourth,
fifth, seventh, and eighth authors). The remaining
programs were delivered by other United King-
dom service providers, either funded directly by
the parents or purchased for the parents by their
Local Education Authority. These included
PEACH, a parent charity (n!4), London Early
Autism Program (n!1), United Kingdom–Young
Autism Progamme (n!1), and East Sussex Local
Education Authority (n!1). The remaining child
spent 9 months with PEACH, 9 months with a
private consultant, and the final 6 months at a
school where applied behavior analysis was regu-
larly employed (he was the only child to attend
such a school).
Although interventions were delivered by a
range of service providers, they had in common
the 10 features characterizing research-based in-
terventions identified by Green et al. (2002, p. 70).
Treatment began in the home during the chil-
dren’s 3rd or 4th year and continued for 2 years.
It involved 20 to 30 hrs a week of structured
teaching, based on the principles of applied be-
havior analysis. Thus, programs used discrete trial
training methods (Lovaas, 1993) and incorporated
generalization procedures to extend and maintain
emerging behavioral repertoires. Elements of nat-
ural environment training (Sundberg & Parting-
ton, 1999) and verbal behavior (Partington &
Sundberg, 1998) were also integrated into the ma-
jority of the interventions.
In some cases, recognized alternative and aug-
mentative communication systems based on be-
havioral principles were incorporated into inter-
ventions to address absence of speech and provide
children with an initial means of communication.
At 12 months, 44% (10) of the children in the
intervention group were using the Picture Ex-
change Communication System and 17% (4) con-
tinued to do so at 24 months. For sign language
or Makaton Communication Systems, the figures
were 44% (10) at 12 months and 35% (8) at 24
months, respectively.
Intervention programs covering all aspects of
functioning (e.g., language, other cognitive, social,
motoric) were individualized for each child, based
on ongoing analysis of current strengths and
needs, taking into consideration typical develop-
mental trajectory and practicability. Programs
were thus progressive: When simpler skills were
acquired, more complex skills were established as
behavioral objectives, and this process continued
throughout the 2 years of intervention. Similarly,
as children’s skills increased, the process of facil-
itating access to appropriate school settings was
initiated.
The program was delivered to each child by
a team of 3 to 5 therapists trained in the use of
behavior analytic procedures (e.g., shaping, chain-
ing, prompting, fading, modeling, discrimination
learning, task analysis, functional analysis) and su-
pervised by more experienced staff members, in-
cluding a supervisor who had substantial experi-
ence with early intensive behavioral intervention
and, in the majority of cases, a consultant with
still greater experience to PhD level and/or a track
record of research publication in behavior analy-
sis. Parents also delivered therapy, which was su-
pervised in the same way.
Supervision of each tutor team was accom-

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plished using a workshop model in which super-
visors arranged extended team meetings at regular
intervals. The frequency of team meetings de-
pended on the service provider; for the 13 chil-
dren receiving University of Southampton super-
vised intervention, meetings were twice a month,
with additional regular training overlaps; for the
remaining children, meetings were less frequent
(range !4 to 12 weeks). During meetings, the
child’s progress since the previous meeting was as-
sessed, programs were added or modified, and
members of the team (including the parents) prac-
ticed the programs to be implemented next. Con-
sultants attended meetings on a less frequent basis
(on average, once every 2 months), but they were
available by telephone or email to provide addi-
tional clinical supervision. Between meetings, su-
pervisors were similarly available to the team and
parents.
No child in the intervention group was at-
tending school at the baseline assessment, but by
the 12-month assessment, 13 (57%) attended a
mainstream school for an average of 5.8 hrs per
week. At the 24-month assessment, 17 children
(74%) attended mainstream school for an average
of 13.28 hrs per week; and 22% (5), a special
needs school for an average of 9.15 hrs per week.
The remaining child continued with only the
home-based program. Because most children in
the intervention group were simultaneously at-
tending school and receiving home programs,
school hours were somewhat lower than those for
the comparison group children at the first and sec-
ond year of the study. Treatment and Education
of Autistic and Related Communication Handi-
capped Children TEACCH principles (Schopler,
Mesibov, & Baker, 1982) were sometimes incor-
porated into school provision of 2 children (9%)
receiving this intervention at the 12-month as-
sessment and 13% (3) at the 24-month assess-
ment).
Apart from behavioral treatment and school-
ing, some children in the intervention group also
received other interventions: 65% (15) were re-
ceiving speech therapy at the baseline assessment;
22% (5), at the 12-month assessment; and 26%
(6), after 24 months. Dietary interventions (typi-
cally gluten and casein restriction) were also com-
monly reported, with 11 children (48%) on re-
stricted diets at baseline, and 14 (61%) and 12
(52%) at the 12 and 24 months, respectively. Fi-
nally, parents also reported the use of routine pre-
scription medication: 4% (1) at baseline, 17% (4)
at the 12-month assessment, and 4% (1) at 24
months. Vitamin injections or high doses of vi-
tamins were given to 6 children (26%); 10, 44%;
and 7, 30%, respectively, at baseline, 12-, and 24-
month assessment; and homeopathic interven-
tions, 5 children (22%) at baseline; 2 (9%) at 12
months; and 1, 4% at 24 months.
Comparison group. The children in the com-
parison group received their local education au-
thorities’ standard provision for young children
with autism. Thus, over the course of 2 years, they
experienced a variety of interventions designed to
ameliorate the impact of autism and enhance
functioning, none of which were intensive or de-
livered on a one-to-one basis for the majority of
time. The most frequently reported intervention
was speech therapy: 12 of the children (57%) re-
ceived it at the time of the baseline assessment,
67% (14) at the 12-month assessment, and 48%
(10) at the 24-month assessment. As part of the
children’s experience of school, parents reported
frequent use of TEACCH principles (38%, 8 chil-
dren, and 52%, 11 children at 12 months and 24
months, respectively). Similarly, the Picture Ex-
change Communication System was frequently
employed:(67%, 14 children and 76%, 16 chil-
dren, respectively, at 12 and 24 months) and sign
language or Makaton communication systems
(24%, n!5 and 48%, n!10, at 12 and 24
months) were used as alternative communication
systems. Dietary interventions were also relatively
common, with 14% (n!3) on special diets at
baseline, 19% (n!4) at their 12-month assess-
ment, and 29% (n!6 children) at the 24-month
assessment. Prescription medication, vitamin, and
homeopathic use were also reported: 5% (1 child)
received prescription medication at baseline, 24%
(5) at 12 months, and 19% (4) at 24 months. Vi-
tamin injections or high doses of vitamins were
not used with any of the children at baseline, and
only 1 child (5%) at the 12- and 24-month assess-
ments. Finally, homeopathic interventions were
reported for 24% (5) of the sample at baseline,
and for only 1 child (5%) at the 12- and 24-month
assessments.
No child in the comparison group was at-
tending school at baseline assessment. By the time
of their 12- and 24-month assessments, however,
in line with their education authorities’ standard
provision, all had a school placement. At the 12-
month assessment, 48% (6) were in a mainstream
environment; 43% (9), in a special educational
needs school, and 10% (2), a mixed placement in

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which half their time was spent in each kind of
school. The average number of hours per week
spent at school was similar for each child no mat-
ter where they were placed (an average of 15.3 hrs
spent in mainstream, 17 hrs spent in special
needs, and 15 hrs spent in mixed placements). By
their 24-month assessment, 48% (10 children)
were in mainstream schools for a weekly average
of 22.3 hrs and 52% were in special needs schools
for 13.6 hrs per week.
Although intervention and comparison group
children received similar levels of speech and lan-
guage interventions at baseline, it is clear that this
pattern was not sustained throughout the 24-
month period. Typically, as reported below, this
was because the intervention produced effects that
reduced the need for other interventions such as
sign language or Makaton.
Psychometric assessments. Outcome measures
for children and parents were obtained at baseline,
after 1 year of behavioral intervention or standard
provision (12-month assessment), and after 2 years
(24-month assessment). Performance-based tests
were administered in a distraction-free environ-
ment at the family home. All questionnaires were
mailed out to parents at the time of each of the
three assessments and returned to research staff
shortly afterwards. Telephone interviews using the
Vineland were conducted with primary caregivers
approximately 1 week prior to the children’s as-
sessment visits, which took place at the family
home. These lasted approximately 60 min. Except
for the Autism Diagnostic Interview, which the
final author administered to parents in the home
at the time of the baseline assessment, the third
author administered all the standardized outcome
measures using a uniform order of administration:
(a) the Early Social Communication Scales, (b)
the Bayley Scales of Infant Development or the
Stanford Binet, and (c) The Reynell Developmen-
tal Language Scales (which was administered only
if a child’s language level was such that they could
access the items on the test).
Results
Overview of Analysis of Group Data
To evaluate the effectiveness of behavioral in-
tervention, we used ANCOVA models. Because
the groups were not actively matched at baseline,
baseline scores on outcome measures were entered
as a covariate into analyses that, therefore, con-
sisted of one between-groups factor: Group (in-
tervention, comparison) and one repeated mea-
sures factor, Time (outcomes at 12 months vs. 24
months). In these models, a significant main ef-
fect of group would suggest larger changes in one
group seen at both 12 and 24 months. A signifi-
cant Group "Time interaction would likely in-
dicate that there were no significant between-
group differences at one time point, but signifi-
cant between-group differences at the other time
point. Finding no main effects or interaction ef-
fects would suggest that the two groups did not
differ after either 12 and 24 months.
For ease of comparison with other research
and to facilitate later meta-analytic comparisons,
unadjusted mean scores for outcome variables at
baseline and at 12- and 24-month assessments are
displayed in Tables 2 and 4 (children) and Table
5 (parents).
Child outcome. Table 2 displays the results for
IQ, MA, raw scores on the Vineland subdomains,
and the Early Social Communication Scale mea-
sures of Initiating and Responding to Joint Atten-
tion. The 2 "2 ANCOVA model, used to ana-
lyze outcomes at 12 and 24 months, revealed that
four of these measures showed an advantage at 12
months for the intervention group over the com-
parison group that was maintained through to the
24-month assessment point. For IQ, there was a
significant main effect of group, F(1, 41) !7.72,
p!.008, but no interaction effect. Similarly, MA
showed a significant main effect of group,
F(1, 41) !8.37, p!.006, but no interaction ef-
fect. Significant group effects (but no interactions)
were also found for Vineland Daily Living Skills,
F(1, 41) !6.32, p!.016, and Vineland Motor
Skills, F(1, 41) !4.49, p!.040, but not for the
Vineland Composite score nor the Socialization
and Communication domains. In all cases, chil-
dren receiving early intensive behavioral interven-
tion were out-performing children in the compar-
ison group.
Seven children (2 in the intervention and 5
in the comparison group) were unable to partici-
pate in the baseline Early Social Communication
Scale assessment because of behavioral problems,
inattention, or absence of parental agreement to
videorecording. However, employing Mann-
Whitney tests, we were not able to identify dif-
ferences at baseline, in terms of CA or outcome
measures, between those children who accessed
the assessment and those who did not. For those
children who did, the 2 "2 ANCOVAs for 24-
month outcomes showed a significant main effect

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Table 3. Frequencies of Children by Group
Achieving a Score on the Reynell Verbal
Comprehension Scale and Expressive Language
Scale at Three Assessment Points
Assessment
time/Group
Reynell Verbal
Comprehension Scale
Verbal
comprehension
Expressive
language
Baseline
Intervention 4 2
Comparison 3 1
12-month
Intervention 19 17
Comparison 11 8
24-month
Intervention 21 21
Comparison 11 10
Note. Intervention group n!23 and comparison group,
n!21.
of group for responding to joint attention in favor
of the intervention group, F(1, 34) !4.15, p!
.049, but no significant effect for initiating joint
attention. Neither measure yielded significant in-
teraction effects again, indicating that the effects
were established by 12 months and maintained to
24 months.
Given that the baseline CAs of the interven-
tion and comparison groups (35.7 and 38.3
months, respectively) differed significantly and
that CA was correlated with IQ, MA, and some
Vineland scores, we ran further ANCOVAs for
these variables, with CA as an additional covari-
ate. Three of four of the group effects described
above similarly remained significant at conven-
tional levels, but the Vineland Motor Skills main
effect achieved only marginal significance, p!
.057.
Unfortunately, when tested, some children
were unable to obtain a score on the Reynell De-
velopmental Language Scales, particularly at base-
line, owing to the higher norms produced for the
third edition of the test (Edwards et al., 1997).
Thus, the raw data for this measure were incom-
plete. Therefore, we evaluated group effects on the
Reynell using a frequency analysis in which the
numbers of children obtaining versus those not
obtaining a score on the Reynell were compared
at the three data-collection points using 2 "2 chi-
square tests. The group frequencies are shown in
Table 3. These tests revealed no differences be-
tween groups at baseline for comprehension, but
significant differences in favor of the intervention
group both at 12 months, %
2
(1, N!44) !4.13,
p!.042, and 24 months, %
2
(1, N!44) !8.39,
p!.004. Similarly, the groups did not differ at
baseline for expressive language, but significant
differences in favor of the intervention group were
observed both at 12 months, %
2
(1, N!44) !
5.02, p!.025, and 24 months, %
2
(1, N!44) !
10.06, p!.002.
Table 4 shows mothers’ and fathers’ ratings of
their child’s behavior problems, prosocial behav-
iors, and autistic behavior. Analyses of covariance
at 24 months revealed a significant group effect
for mother-reported positive social behavior,
F(1, 41) !9.07, p!.004, and a marginally sig-
nificant group effect for fathers on this scale,
F(1, 28) !4.09, p!.053. In both cases, more
positive social behavior was reported for the in-
tervention group. No further significant main ef-
fects of group and no interaction effects were
found for the other parentally reported child var-
iables.
Parental outcome. Table 5 shows scores on ma-
ternal and paternal well-being measures across the
2 years of the study. The only significant finding
was a group main effect for paternal depression.
Fathers in the intervention group reported more
symptoms of depression at both 12 and 24
months, as revealed by a significant main effect
in the 2 (group) "2 (time) ANCOVA, F(1, 28)
!5.19, p !.031.
Analysis of Outcomes for Individual Children
Because IQ has been the primary outcome
variable in previous early intensive behavioral in-
tervention research, and here showed the stron-
gest positive change as a result of intervention, we
used IQ as the focus for analysis of change for
individual children. We first calculated a group
effect size for IQ at 24 months to reinforce the
clinical significance of the overall intervention ef-
fect. The estimate of effect size was based on Co-
hen’s dstatistic. Specifically, the mean difference
between the two groups’ IQ change scores after
24 months was used as the numerator and the
pooled SD of the two groups’ IQ change scores
as the denominator using Cohen’s formula (J. Co-
hen, 1988). The 24-month effect size for IQ cal-
culated using this method was .77, indicating a

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Table 4. Unadjusted Means (SDs) of Parental Rating Scales for Child Behavior by Group and Assessment Point
Measure parent
a
Baseline
Intervention Comparison
12-month assessment
Intervention Comparison
24-month assessment
Intervention Comparison
Developmental Behavior Checklist M 50.26 (22.75) 67.81 (18.77) 45.57 (18.79) 57.71 (22.61) 44.70 (24.20) 60.62 (24.72)
Total score F 46.67 (22.15) 57.57 (15.67) 43.67 (16.28) 58.02 (21.05) 45.19 (20.94) 55.20 (19.44)
Developmental Behavior Checklist M 22.22 (9.54) 31.14 (9.22) 20.39 (8.54) 25.38 (10.94) 18.91 (10.29) 26.76 (11.21)
Autism Algorithm F 22.33 (9.92) 26.29 (8.90) 19.53 (8.23) 25.12 (10.43) 19.50 (8.80) 24.00 (11.60)
Nisonger Child Behavior Rating Form: M 10.57 (4.24) 9.29 (3.47) 15.22 (4.09) 11.00 (4.10) 15.30 (4.69) 11.86 (4.84)
Positive Social Behavior F 8.94 (3.47) 8.73 (3.67) 13.06 (3.04) 10.40 (4.75) 12.69 (4.06) 11.20 (5.19)
Autism Screening Questionnaire M 19.26 (4.93) 21.14 (5.47) 16.43 (5.56) 20.14 (6.55) 15.96 (5.63) 19.29 (7.22)
F 20.88 (4.54) 21.07 (6.41) 18.44 (5.54) 20.73 (7.45) 19.88 (6.16) 19.47 (7.46)
Note. Intervention group mothers (M) n!23 and comparison group mothers, n!21. Intervention group fathers (F) n!16 and comparison group fathers n!15.
relatively large difference between the groups ( J.
Cohen, 1988, considers a dof .80 to be the thresh-
old for a large effect).
To explore whether this difference at the
group level was reflected in outcomes for individ-
ual children, we applied the criteria outlined by
Jacobson and Truax (1991) to establish thresholds
for both reliable and clinically significant change
for the intervention and comparison groups. The
computation of a reliable change index score can
be used to establish the IQ change beyond which
there is a 95% chance that the observed change
does not result from measurement unreliability
and/or underlying variability in scores. Calculat-
ing the reliable change index score requires two
pieces of data: the SD of IQs and the stability of
the IQ measure. We adopted a conservative ap-
proach to the process of identifying these values.
Because there were no suitable sources of nor-
mative information regarding variance in, and sta-
bility of, IQ in very young children with autism,
we used the data from the present sample of chil-
dren rather than drawing on normative informa-
tion provided by the Stanford-Binet or Bayley
tests (i.e., the SD for IQ is normally 15). First, we
identified the SD for IQ for our combined sample
of 44 children at baseline. Second, we assessed the
2-year stability of IQ for young children with au-
tism using the correlation between baseline and 2-
year IQs for the comparison (untreated) group
only. This provided the best available estimate of
typical stability in IQ for young children with au-
tism. Substituting these values in Jacobson and
Truax’s formula (1991, p. 14) indicated a reliable
change index at the standard level of 1.96 equated
to a change of 23.94 IQ points; a child’s IQ after
2 years had to deviate from that obtained at base-
line by at least that amount before the change was
considered reliable; IQ change scores for each
child are shown in Figure 1. This reflects the over-
all group effect, in that more children in the in-
tervention group than the comparison group
showed IQ increases over time. Moreover, it
shows that 6 children in the intervention group
(26%) achieved a reliable improvement over the 2
years of the study. Three of the children (14%) in
the comparison group did the same but 3 (almost
4) children in this group (14% to 19%) also re-
gressed reliably.
Although the use of the reliable change index
improves on the methods for establishing best
outcome used in previous studies by providing a
quantifiable assessment for individual children, it

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Table 5. Unadjusted Means (SDs) of Self-Report Measures of Parental Well-Being by Group and
Assessment Point
Measure
Baseline
Intervention Comparison
12-month assessment
Intervention Comparison
24-month assessment
Intervention Comparison
Stress (QRS-F)
a
Mother 6.43 (4.29) 7.24 (4.19) 7.48 (4.70) 6.48 (4.08) 8.52 (2.97) 8.29 (2.17)
Father 6.81 (4.26) 5.87 (3.19) 7.88 (4.27) 5.53 (3.00) 8.94 (3.62) 7.60 (2.72)
HADS
b
Anxiety
Mother 9.35 (4.21) 9.76 (4.87) 10.48 (5.12) 8.52 (4.72) 9.13 (4.53) 8.62 (4.43)
Father 8.89 (4.76) 7.93 (3.67) 7.87 (4.60) 7.00 (3.16) 8.38 (4.08) 8.13 (4.10)
Depression
Mother 8.13 (4.12) 8.71 (3.68) 8.04 (5.80) 7.19 (4.26) 7.09 (4.97) 6.90 (3.94)
Father 5.69 (4.42) 7.07 (3.61) 6.56 (5.25) 5.27 (2.99) 7.00 (5.34) 5.93 (3.83)
Positive
Perceptions
(KIPP-PC)
c
Mother 127.30 (27.00) 133.10 (19.37) 127.39 (23.79) 133.43 (18.23) 128.00 (19.62) 132.43 (17.94)
Father 120.94 (20.23) 124.73 (19.66) 122.56 (19.70) 131.40 (15.68) 122.81 (22.47) 128.53 (9.70)
a
Questionnaire on Resources and Stress Friedrich short form.
b
Hospital Anxiety and Depression Scale.
c
Kansas Inventory
of Parental Perceptions Positive Contributions scale.
Figure 1. IQ change for children in the intervention and comparison groups. Horizontal bars indicate
change in IQ between baseline and 24-month assessment for each child in the intervention group (left
panel) and comparison group (right panel). Black vertical lines with arrow-points on both panels indicate
the upper and lower bounds for reliable change in IQ calculated according to Jacobson and Truax’s
(1991) criteria. EIOI !early intensive behavioral intervention.

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is not sufficient to establish the clinical meaning
of outcomes. A child’s IQ might change reliably
without moving his or her score beyond the se-
verely impaired range. Thus, it is useful to identify
an IQ above which one would consider a child to
be more like children from the typical population
than the population of children from which the
sample was drawn. Jacobson and Truax (1991) dis-
cussed several criteria for establishing the clinical
significance of outcomes. Their Criterion C is rec-
ommended for use when, as in the present case,
it is possible (a) to identify the nonclinical distri-
bution of an outcome variable (e.g., IQ) and (b)
to obtain reasonable information about the distri-
bution of the variable in a clinical population.
Under Criterion C, the IQ indicating clinical
change is halfway between the mean baseline IQ
of the children in the present sample and the typ-
ical population mean (100). This IQ is 81.93. Af-
ter 2 years, 5 of the 6 children in the intervention
group who achieved reliable change also achieved
clinically significant change (i.e., their IQs exceed-
ed 81.93); all 3 children in the comparison group
achieving reliable improvement also achieved
clinically significant change. No other children in
either group achieved a change that was both re-
liable and clinically significant.
Exploratory Analysis of Variables Associated
With IQ Change
Figure 1 is a striking representation of the im-
pact of early intensive behavioral intervention;
many more children in the intervention than the
comparison group achieved positive outcomes.
This, however, begs the question of what factors
might be related to intervention success. To con-
sider this, we explored descriptive data on reliable
change index-defined responders (the 6 children re-
ceiving early intensive behavioral intervention
whose IQ changed positively to a reliable extent)
and nonresponders (the 6 children in the interven-
tion group whose IQs decreased (cf. Sherer &
Schreibman, 2005). Although we are using the
term nonresponders, the data presented in Figure 1
suggest that these 6 children’s IQs dropped less
than might be expected by comparison with the
poorest outcome children in the comparison
group. The relativity of the term should, there-
fore, be borne in mind. Table 6 shows mean
scores on all continuous variables at baseline for
these two small subgroups of children. Means
were compared by calculating Cohen’s dfor each
measure. Using rules of thumb suggested by Co-
hen (1985), we considered differences between re-
liable change index responders and nonrespond-
ers to be worthy of comment if they exceed .50
(medium effect) and .80 (large effect).
These exploratory analyses suggested that
children who responded most positively to behav-
ioral intervention differed from nonresponders at
baseline in the following ways: They had higher
IQ, higher MA, higher Vineland Composite,
Communication and Social Skills scores, lower
Vineland Motor skills scores, more behavior prob-
lems reported on the Developmental Behavior
Checklist by both mothers and fathers, more au-
tistic symptoms reported on the Developmental
Behavior Checklist Autism Algorithm by both
mothers and fathers, and fewer hours of interven-
tion in Year 2.
We also considered the baseline data from the
3 children in the comparison group whose IQ in-
creased to a reliable and clinically significant ex-
tent over the 2 years of the study. Because they
were very few in number, we were not able to
complete formal statistical comparisons, but a vi-
sual inspection of their scores on all measures at
baseline showed no discernable pattern as a po-
tential explanation as to why they showed reliable
improvement.
Discussion
The data from this 2-year controlled compar-
ison of early intensive behavioral intervention
against treatment as usual within the United King-
dom education system show a positive advantage
for the intervention group. Consistent with other
field effectiveness research in this area, robust
group main effects were found for IQ, MA, Rey-
nell Expressive Language and Language Compre-
hension, and Vineland Daily Living Skills after 24
months of intervention. Although less robust,
there were also significant changes in Vineland
Motor Skills and Responding to Joint Attention
as measured by the Early Social Communication
Scales. Like H. Cohen et al. (2006), we used AN-
COVA methods to explore Group "Time inter-
actions that would indicate increasing differenti-
ation of performance with continued interven-
tion; and like Cohen et al., we found none.
Although we included a broader range of out-
come measures than did previous researchers (H.
Cohen et al., 2006; Howard et al., 2005), the im-
pact of behavioral intervention was almost exclu-

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Table 6. Baseline Means (SDs) and Effect Sizes of Child Measures for Most and Least Positive
Responders in the Intervention Group
Baseline scores
Most-positive responders
Mean SD
Least-positive responders
Mean SD Effect size
IQ 65.00 19.81 47.67 11.55 1.07
MA 22.50 6.98 18.00 4.82 0.75
VABS
a
Composite 107.17 12.75 99.50 12.28 0.61
Communication 24.17 8.66 16.17 5.04 1.13
Daily living 21.17 6.34 21.17 3.82 0.00
Social 28.67 3.20 25.67 2.50 1.04
Motor 33.17 3.54 36.50 6.38 &0.65
ASQ
b
Mothers 21.67 5.28 21.17 4.49 0.04
Fathers 22.00 7.21 22.67 3.50 &0.14
DBC
c
Total
Mothers 69.67 18.24 51.83 24.05 0.84
Fathers 73.67 9.29 49.80 24.57 1.12
DBC ASA
d
Mothers 28.67 8.96 23.83 10.80 &0.49
Fathers 34.00 8.00 24.40 9.89 &1.02
Intervention hours
Year 1 970.08 342.11 1009.88 113.92 &0.16
Year 2 760.58 533.53 1053.42 356.97 &0.65
a
Vineland Adaptive Behavior. Scales Raw Scores.
b
Autism Screening. Questionnaire.
c
Developmental Behavior Checklist.
d
Autism Screening Algorithm.
sively on children’s cognitive and language abili-
ties and adaptive functioning. Exceptionally, chil-
dren in the intervention group differentially
showed robust improvements in parental ratings
of positive social behaviors, but there was no ev-
idence of a similar change in parents’ reports of
children’s behavior problems or ratings of their
autistic behaviors. In addition, there were less
marked improvements in joint attention. Sallows
and Graupner (2005), using domain scores from
the ADI-R, also showed reductions in autism
symptoms relating to social and communication
deficits but no change in ritualistic behaviors.
However, it is not clear whether these scores
would have changed without intensive interven-
tion as there was no nonintensive intervention
comparison group.
The absence of a relative reduction in report-
ed problem behaviors following early intensive be-
havioral intervention is somewhat surprising. It
should be remembered, however, that because in-
tervention focuses primarily on educational goals,
detailed functional analysis and function-in-
formed interventions for problem behaviors are
not the most prominent components. Neverthe-
less, given the known association between behav-
ior problems and severity of cognitive and adap-
tive functioning, especially language/communi-
cation skills (e.g., McClintock, Hall, & Oliver,
2003), positive benefits of early behavioral inter-
vention on child behavior problems might have
been expected. It is possible that the increased
ability of the children in the intervention group
to respond to bids for attention might have led
to the enhancement of their parents’ positive per-
ceptions of their prosocial behavior. Given the de-
velopmental role of these pivotal skills in facili-
tating language and cognitive development (Mun-

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dy, 1995; Mundy & Crowson, 1997; Mundy &
Neal, 1997), this is an important direction for fu-
ture research.
The present study also extended earlier re-
search by including a detailed analysis of parental
outcomes and the first data on fathers. As expect-
ed on the basis of previous cross-sectional research
(Hastings & Johnson, 2001), the benefits to chil-
dren of early intensive behavioral intervention did
not appear to be at a cost to parents. There was
no evidence of differentially increased stress or ad-
ditional mental health problems in the interven-
tion group mothers or fathers, although the latter
reported more symptoms of depression over the
course of the study. These fathers, however, had
fewer symptoms at baseline compared with those
in the comparison group, so the result may, in
part at least, be an artifact of a strong regression
to the mean effect after 12 and 24 months. These
findings are important because difficulties in pa-
rental adjustment would reasonably be considered
as a contraindication for a home-based behavioral
intervention that requires the daily involvement
of the family.
Overall, the effect size for the impact of the
intervention on the children participating was
substantial and clinically meaningful at the group
level (Cohen’s dapproaching .80 for IQ after 2
years). Although not reported by H. Cohen et al.
(2006), the effect size for IQ in that study closest
in design to our own was slightly higher than that
obtained in the present research (calculated from
data presented in Cohen et al. as roughly .90).
Thus, our findings are comparable, despite the in-
terventions being delivered over a shorter period
of time and with fewer intervention hours. In ear-
lier studies, the impact of intervention at the level
of individual participants was rarely quantified; in-
stead, researchers tended to report the number of
children scoring within the normal range on stan-
dardized measures. In the present study, we ex-
tend knowledge by using Jacobson and Truax’s
(1991) reliable change index statistic as a precise
criterion for ‘‘best outcome.’’ This revealed that
26% of children receiving early intensive behav-
ioral intervention achieved IQ change that was
statistically reliable, and none showed a corre-
spondingly reliable regression in IQ. In the com-
parison group, 14% improved reliably but, unfor-
tunately, a further 14% regressed reliably.
The reliable change statistic also provides a
principled criterion for identifying variables that
are common to the children who benefit most
from early intensive behavioral intervention. Ex-
ploratory analysis of reliable change index-defined
most- and least-positive responders identified cor-
relates of change also identified in previous stud-
ies (e.g., H. Cohen et al., 2006; Sallows & Graup-
ner, 2005). These included differences on higher
baseline intellectual functioning and adaptive be-
havior skills (including the total score, commu-
nication, and social skills) among the positive re-
sponding group. Differences not previously iden-
tified were also observed. In addition to poorer
motor skills, the most positive responders had
more behavior problems and more severe symp-
toms of autism at baseline. This seemingly para-
doxical relation could perhaps have arisen if the
measures we used were more sensitive to behavior
in those children exhibiting less severe develop-
mental delay. There are no obvious explanations
for the positive reliable change in IQs observed
for 3 children in the comparison group whose IQs
improved to a reliable extent over 2 years.
The present results indicate that behavioral
intervention can be effective for young children
with autism in the United Kingdom preschool ed-
ucation context, a system unlike the United Sta-
tes whose administrators and educators are not
familiar with early intensive behavioral interven-
tion and, in some ways, are institutionally unsup-
portive of it. For example, parents in the United
States benefit from Public Laws 94-142 (1975) and
99-457 (1986), which established a right to early
intervention services for children from birth to
age 3 (the Handicapped Infants and Toddlers Pro-
gram: Part H). The United Kingdom has no such
legislation, and many of its education authorities,
during the time of the research, routinely opposed
parental attempts to access early intensive behav-
ioral intervention through public provision ( John-
son & Hastings, 2002). For these reasons, it was
not possible to exert a high degree of control of
many practical aspects of the delivery of the in-
tervention. For example, tutors delivering home-
based services were not employed by the research-
ers but by education authorities or the children’s
families. Staff turnover was common and replace-
ment tutors often difficult to obtain and slow to
train. Thus, although an intervention group target
intensity of 40 hours per week of input for 2 years
was set, positive results were achieved with an av-
erage of only 25.6 hours per week. Nevertheless,
as required for a convincing demonstration of the
field effectiveness, the expected positive outcomes
were achieved despite these difficulties.

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Outcome of early intervention for autism B. Remington et al.
Like most applied research in early intensive
behavioral Intervention, the present study had a
number of limitations. First, because it was not a
randomized control trial, the few potentially rel-
evant differences detected between groups at base-
line (such as CA at treatment onset) had to be
controlled statistically, not experimentally. It is,
therefore, possible that, although we took the
most rigorous steps possible in a study of this kind
to manage pre-existing group differences, some re-
mained unobserved. Parenthetically, unobserved
differences between groups prior to intervention
may also occur under conditions of randomiza-
tion with samples of the size typically used in ear-
ly intervention research (Drew et al., 2002). In any
case, it would have been very difficult to execute
a randomized control trial in the present case, be-
cause the independent variable is an extended ed-
ucational intervention that cannot be delivered
‘‘blind’’ and that has already amassed a consider-
able body of research attesting to its utility. Given
the difficulties in finding an equally credible pla-
cebo treatment, it might reasonably be expected
that many parents whose children are randomly
assigned to a control group would remove them
from the study and of these, a percentage would
seek the intervention elsewhere (Lord, Wagner et
al., 2005). Under these circumstances, intention to
treat analyses could be misleading. Perhaps for
these reasons, recently published studies in this
area (e.g., H. Cohen et al., 2006; Howard et al.,
2005) have eschewed randomization.
Procedurally, randomized control trials typi-
cally include a precise intervention, often de-
scribed in a manual; narrow participant selection
criteria and blind assessment. Manualized treat-
ment was not a feature of the present study in
part because we chose to adopt broad inclusion
criteria. It would have been impractical to produce
a detailed manual dealing with all possible exigen-
cies but, additionally, the researchers were not in
a position to determine the course of therapy for
all children in the intervention group who, as not-
ed, received services from a range of providers.
Nevertheless, all interventions were supervised by
experienced clinicians with detailed knowledge of
behavioral programming, and we are confident of
the quality of program management. In fact, prac-
tical problems of treatment fidelity, primarily the
result of tutor shortages, were far more significant
than those of treatment coherence. Regarding po-
tential examiner bias, the assessor was indepen-
dent of the intervention teams and formally
‘‘blind,’’ but, again for practical reasons, assess-
ment took place in the children’s homes, and in
some cases physical or behavioral cues may have
signaled the treatment they were receiving. We
suspect that it is difficult to control for cues of
this kind in any study where there is widespread
professional knowledge of the nature of the inter-
vention.
The issue of sample size restriction in the
present study also requires consideration. Al-
though we were able to recruit a sample of a size
similar to that reported in other early intensive
behavioral intervention evaluation research, there
is a general problem of statistical power in studies
of this kind. Here, two issues are particularly wor-
thy of further comment. First, we found main ef-
fect differences on key child outcomes but no sig-
nificant interaction terms in the 2 "2 ANCOVA
models. This finding could mean, as H. Cohen et
al. (2006) concluded, that the effects of the inter-
vention were established by 12 months. We can-
not, however, reliably draw such a conclusion: It
is possible that change over the second 12 months
was less marked but that in a larger sample we
might have seen the advantage for the interven-
tion group continuing to increase. More research
addressing this question is needed. A second issue
is that we found very little evidence of negative
effects of early intensive behavioral intervention
involvement on parental well-being, but in a larg-
er sample such effects may have been observed.
Although this possibility cannot be eliminated, it
is important to consider that the present sample
would have been sufficient to show significant or
marginal effects that would clearly have become
significant with more power. It is also salient that
our findings concur with the results of all existing
studies in which investigators addressed this ques-
tion using various designs; none show evidence of
a negative effect on family members’ adjustment.
The sample-size restriction also allowed only
exploratory effect size analyses of differences be-
tween those children in the intervention group
who responded most positively and those who re-
gressed. However, this method has some potential
for application in other outcome studies and may
contribute to the process whereby intervention
may be focused on children and their families
whose characteristics suggest may maximally ben-
efit from intervention.
In conclusion, the present study indicates that
intervention for childhood autism based on ap-
plied behavior analysis and delivered intensively

!American Association on Intellectual and Developmental Disabilities 435
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at home during the preschool period can bring
about significant changes in children’s function-
ing without a negative impact on other family
members, even when delivered in circumstances
that for practical reasons do not permit its opti-
mum implementation. Questions remain, how-
ever, regarding both the factors that best predict
the effectiveness of intervention and the long-
term impact of the effects reported. Although par-
ents, educators, and policy makers are likely to ask
whether early intensive behavioral intervention
‘‘works’’ or ‘‘does not work,’’ it may be more fruit-
ful to pose, instead, smaller but potentially more
answerable questions regarding the selection of
children for intensive intervention: the identifi-
cation and evaluation of effective curricula and
teaching methods, and the most effective forms
of maintenance programs for children at the end
of a fixed period of early intervention.
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11 Local Education Authorities in the South of
England including Southampton, Hampshire,
East Sussex, Maidenhead and Windsor, Poole,
Brighton and Hove, Wokingham, Wiltshire, and
Bournemouth) funded the University of South-
ampton’s intervention services for 13 children in
the intervention group. The remaining 10 chil-
dren in that group received services from PEACH,
the London Early Autism Program, and the UK–
Young Autism Progamme. The authors acknowl-
edge the collaborative support of all these agen-
cies, whether financial and practical, without
which the study reported here would not have
been practicable. Any opinions expressed herein
are those of the authors and are not necessarily
endorsed by the research sponsors or collabora-

438 !American Association on Intellectual and Developmental Disabilities
VOLUME
112,
NUMBER
6: 418–438 !
NOVEMBER
2007
AMERICAN JOURNAL ON MENTAL RETARDATION
Outcome of early intervention for autism B. Remington et al.
tors. Francesca degli Espinosa was the senior su-
pervisor and Erik Jahr served as the external con-
sultant for the University of Southampton inter-
vention. The authors thank: Ruth Littleton, So-
phie Orr, and Penny Piggott who, with Paula
Alsford and Monika Lemaic, held supervisory
posts on the University of Southampton team;
Corinna Grindle assisted with reliability analyses;
and Catherine Carr provided outstanding admin-
istrative and logistical support to the team. Re-
quests for reprints should be sent to Bob Rem-
ington, Centre for Behavioural Research Analysis
and intervention in Developmental Disabilities
(BRAIDD), School of Psychology, University of
Southampton, Southampton, SO17 1BJ, UK.
E-mail: rer1@soton.ac.uk