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to sing language, <strong>and</strong> (c) PECS was associated<br />
with significantly greater improvements<br />
for <str<strong>on</strong>g>the</str<strong>on</strong>g> participants without h<strong>and</strong>-motor imitati<strong>on</strong><br />
relative to <str<strong>on</strong>g>the</str<strong>on</strong>g> sign language training<br />
(Adkins & Axelrod, 2002; Anders<strong>on</strong>, 2002;<br />
Tincani, 2004).<br />
O<str<strong>on</strong>g>the</str<strong>on</strong>g>r c<strong>on</strong>sequences. Positive behavioral<br />
change was documented in three of <str<strong>on</strong>g>the</str<strong>on</strong>g> studies<br />
(Anders<strong>on</strong>, 2002; Charlop-Christy et al.,<br />
2002; Magiati & Howlin, 2003). The most<br />
comm<strong>on</strong>ly reported behavior c<strong>on</strong>sequence<br />
were significant reducti<strong>on</strong>s in problem behaviors.<br />
Rival Explanati<strong>on</strong>s<br />
A number of rival explanati<strong>on</strong>s might explain<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> positive findings reported in <str<strong>on</strong>g>the</str<strong>on</strong>g> studies<br />
reviewed in this syn<str<strong>on</strong>g>the</str<strong>on</strong>g>sis. However, many of<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g>se rival explanati<strong>on</strong>s can be refuted as a<br />
c<strong>on</strong>sequence of <str<strong>on</strong>g>the</str<strong>on</strong>g> generally high quality of<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> research designs.<br />
First, <str<strong>on</strong>g>the</str<strong>on</strong>g> fact that studies typically employed<br />
observati<strong>on</strong>al coding as <str<strong>on</strong>g>the</str<strong>on</strong>g> primary method<br />
of data collecti<strong>on</strong> could have resulted in observer<br />
or rater bias. However, every study employed<br />
two independent observati<strong>on</strong>al data recorders<br />
<strong>and</strong> secti<strong>on</strong>s of different interventi<strong>on</strong><br />
phases (e.g., baseline, interventi<strong>on</strong>). Moreover,<br />
with str<strong>on</strong>g reliability data reported for<br />
eight of <str<strong>on</strong>g>the</str<strong>on</strong>g> 13 (62%) studies available, c<strong>on</strong>cerns<br />
that measurement variati<strong>on</strong>s in maternal<br />
interacti<strong>on</strong>s were a result of observer bias<br />
are minimized.<br />
Sec<strong>on</strong>d, <str<strong>on</strong>g>the</str<strong>on</strong>g> positive changes of communicati<strong>on</strong><br />
c<strong>on</strong>sequences may have been emerged<br />
as part of maturati<strong>on</strong>. However, this possibility<br />
is mitigated by <str<strong>on</strong>g>the</str<strong>on</strong>g> fact that many behavioral,<br />
social, <strong>and</strong> communicative deficits exhibited<br />
by children with autism spectrum disorders do<br />
not sp<strong>on</strong>taneously remit over time if untreated<br />
(American Psychiatric Associati<strong>on</strong>,<br />
2000). In additi<strong>on</strong>, 12 out of 13 studies used a<br />
single-subject design, <strong>and</strong> single-subject design<br />
methodology establishes <str<strong>on</strong>g>the</str<strong>on</strong>g> casual relati<strong>on</strong>ship<br />
between treatment <strong>and</strong> outcomes by<br />
as series of intrasubject or intersubject replicati<strong>on</strong>s<br />
of treatment effect (Nati<strong>on</strong>al Research<br />
Council, 2001). Fur<str<strong>on</strong>g>the</str<strong>on</strong>g>rmore, in single-subject,<br />
multiple-baseline designs, participants<br />
serve as <str<strong>on</strong>g>the</str<strong>on</strong>g>ir own c<strong>on</strong>trol group. The presence<br />
of a c<strong>on</strong>trol group can serve to separate<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> effects of maturati<strong>on</strong> <strong>and</strong> those of treatments.<br />
Third, <str<strong>on</strong>g>the</str<strong>on</strong>g> fact that <str<strong>on</strong>g>the</str<strong>on</strong>g> experimenter him/<br />
herself implemented <str<strong>on</strong>g>the</str<strong>on</strong>g> treatment in several<br />
of <str<strong>on</strong>g>the</str<strong>on</strong>g> studies could lead to problem with experimenter<br />
bias; that is, <str<strong>on</strong>g>the</str<strong>on</strong>g> experimenter<br />
might influence <str<strong>on</strong>g>the</str<strong>on</strong>g> participant’s resp<strong>on</strong>ses.<br />
However, this c<strong>on</strong>cern is mitigated somewhat<br />
by <str<strong>on</strong>g>the</str<strong>on</strong>g> fact that in most of <str<strong>on</strong>g>the</str<strong>on</strong>g> studies reviewed<br />
(62%), <str<strong>on</strong>g>the</str<strong>on</strong>g> pers<strong>on</strong> implementing PECS was<br />
some<strong>on</strong>e o<str<strong>on</strong>g>the</str<strong>on</strong>g>r than <str<strong>on</strong>g>the</str<strong>on</strong>g> experimenter.<br />
In summary, a number of comm<strong>on</strong> threats<br />
to internal validity were addressed within <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
research designs of <str<strong>on</strong>g>the</str<strong>on</strong>g>se studies. Therefore,<br />
despite such potential threats to <str<strong>on</strong>g>the</str<strong>on</strong>g> generalizability<br />
of <str<strong>on</strong>g>the</str<strong>on</strong>g> practice, <str<strong>on</strong>g>the</str<strong>on</strong>g> syn<str<strong>on</strong>g>the</str<strong>on</strong>g>sis findings<br />
support <str<strong>on</strong>g>the</str<strong>on</strong>g> effectiveness of <str<strong>on</strong>g>the</str<strong>on</strong>g> PECS training.<br />
C<strong>on</strong>clusi<strong>on</strong><br />
74 / Educati<strong>on</strong> <strong>and</strong> Training in Developmental Disabilities-March 2008<br />
The primary focus of this syn<str<strong>on</strong>g>the</str<strong>on</strong>g>sis of <str<strong>on</strong>g>the</str<strong>on</strong>g> literature<br />
was to summarize findings regarding<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> effectiveness of PECS for enhancing <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
functi<strong>on</strong>al communicati<strong>on</strong> skills of children<br />
with ASD. In brief, <str<strong>on</strong>g>the</str<strong>on</strong>g> evidence for <str<strong>on</strong>g>the</str<strong>on</strong>g> interventi<strong>on</strong>’s<br />
effectiveness was provided by studies<br />
that (a) assessed <str<strong>on</strong>g>the</str<strong>on</strong>g> level of adherence to a<br />
st<strong>and</strong>ardized treatment protocol (i.e., treatment<br />
fidelity); (b) utilized appropriate <strong>and</strong><br />
well-executed research designs; (c) used measures<br />
with well-established reliability to assess<br />
outcomes; (d) replicated finding across participants;<br />
<strong>and</strong> (e) employed a follow-up comp<strong>on</strong>ent<br />
to dem<strong>on</strong>strate <str<strong>on</strong>g>the</str<strong>on</strong>g> stability of treatment<br />
effects. Taken as a whole, <str<strong>on</strong>g>the</str<strong>on</strong>g>refore, results of<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> studies reviewed provide evidence for <str<strong>on</strong>g>the</str<strong>on</strong>g><br />
effectiveness of PECS; specifically, PECS is effective<br />
in enhancing functi<strong>on</strong>al communicati<strong>on</strong><br />
skills of individuals with ASD. Therefore,<br />
PECS is recommended as an evidence-based<br />
interventi<strong>on</strong> for this purpose.<br />
Never<str<strong>on</strong>g>the</str<strong>on</strong>g>less, several points should be c<strong>on</strong>sidered<br />
regarding recommending of PECS as<br />
an evidence-based interventi<strong>on</strong>. First, most of<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> participants of <str<strong>on</strong>g>the</str<strong>on</strong>g> studies included in this<br />
syn<str<strong>on</strong>g>the</str<strong>on</strong>g>sis were male (65%), which most likely<br />
is a reflecti<strong>on</strong> of <str<strong>on</strong>g>the</str<strong>on</strong>g> differential prevalence<br />
rates of autism across genders. The pattern of<br />
gains exhibited by <str<strong>on</strong>g>the</str<strong>on</strong>g> participants was similar<br />
for males <strong>and</strong> females, which indicates that<br />
<str<strong>on</strong>g>the</str<strong>on</strong>g> PECS training had <str<strong>on</strong>g>the</str<strong>on</strong>g> same effect regardless<br />
of gender.<br />
Sec<strong>on</strong>d, children in <str<strong>on</strong>g>the</str<strong>on</strong>g> studies were diag-