The majority of infants with autism attain basic motor milestones essentially “on time” (Johnson et al., 1992; Lord et al., 1997; Rapin, 1996a). Although parental report of motor delays in infants with autism was low (9%), reports of motor delays and clumsiness in more complex skills increased to 18 percent during the preschool and school years (Ohta et al., 1987).
Some recent evidence suggests that, based on parents’ reports, sensory-perceptual abnormalities may be among some of the first signs of autism. Lack of responsiveness to certain sounds, hypersensitivity to the taste of foods, and insensitivities to pain are more commonly seen in infants with autism than in typical infants or infants with other developmental disorders (Hoshino et al., 1982). More recently, retrospective parents’ reports of the presence of unusual sensory behaviors (e.g., strange response to sounds, atypical interest in visual stimuli, overexcitement when tickled, unusual visual behavior), and some play behaviors (e.g., play limited to hard objects), discriminated between children with autistic spectrum disorders and typical children during infant and toddler ages (Dahlgren and Gillberg, 1989; Gillberg et al., 1990).
Converging evidence, based on retrospective home video studies, demonstrates very early nonspecific sensory and motor difficulties in infants later diagnosed with autism. Stereotypic behaviors, under- and overreactions to auditory stimuli, unusual postures, and unstable visual attention were found to be characteristic of infants with autism, compared with those with other developmental disorders or with typical children. In addition, autistic symptoms observed during the first year persisted into the second year of life (Adrien et al., 1992, 1993). In another study, poor responsiveness to visual stimuli in the environment, excessive mouthing behaviors, decreased responsiveness to sound (e.g., name being called), and aversion to social touches were found to be characteristic of infants with autism. However, unusual motor posturing and repetitive motor behaviors were not more common in children with autism than in other children, and visual fixations, reduced level of affective range, and stereotyped object play were more generally characteristic of the group with other developmental disorders than of the children with autism, contrary to original hypotheses (Baranek, 1999b). Other researchers using retrospective videotape analyses have not found early sensorimotor abnormalities in children with autistic spectrum disorders (Mars et al., 1998; Osterling and Dawson, 1999; Werner et al., 2000).