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developmental delay groups revealed a delay in motor development (e.g., walking,
prone, and supine) compared to typically developing children. However, the autism
groups (with and without regression) did not reveal elevated rates of movement
abnormalities or fewer protective responses, whereas the developmental delays group
displayed higher rates of movement abnormalities in sitting and prone and fewer
protective responses in crawling than the other groups. The authors suggest that
children with general developmental delays show the most substantial abnormalities
in the rate and quality of motor development. Thus, early signs of motor delay may
simply be a consequence of developmental disorder in general rather than specific to
ASDs.
These data suggest that home videos of infants who later on develop ASDs
reveal that these infants already manifest difficulties and impairments in
communication, social relationships and sensory motor development. In the very
earliest time period studied (the first 6 months of life), dyadic and intersubjective
abnormalities have been detected, as well as reduced amounts of time paid to social
stimuli. By the end of the first year of life a wide range of triadic early social-
communicative differences are apparent (at least at a group level): reduced orienting
to name; impoverished joint attention behaviors; some early motor abnormalities and
reduced emotional expression. Home video studies enroll participants based on their
current diagnoses and then their development is examined during younger ages prior
to receiving the diagnoses. Although these earlier behaviors from a younger age
distinguished children who developed ASDs later on compared to children with non-
ASD diagnoses and typically developing children, we have no data regarding children
who may manifest these same early behaviors during the first year or two of life but
who do not develop ASDs later on. Data on children who do and do not continue to