The role played by genetic factors in the incidence of ASD has led to studies of infants siblings of children with ASD. Observations of poor responsiveness to language in older children with ASD suggest the possibility that abnormal attention to language may be one root of the communication deficits in this population. Research in infant speech perception has demonstrated that preferences for listening to speech-like sounds change late in the first year from those that apply to any language toward those tuned to the sound patterns of the ambient language. We (Paul et al., 2007) have shown previously that there are significant differences in preferences for speech-like input between toddlers identified with ASD and TD peers.
This study reports on differences in auditory preferences in the first year of life in siblings of children with ASD.
Participants. High Risk (HR) participants had a full sibling with a validated diagnosis of ASD. Low Risk (LR) infants had no sibling who had received a diagnosis of autism. Infants were seen multiple times during their first year. At 18 and 24 months, clinical identification of the presence/absence of autistic symptoms by experienced clinicians was also assessed. The present report examines data from the 9 month visit, and uses diagnostic data from the 18 and 24 month visits to assign children to three groups:
LR: children with low risk for autism, with no affected sibling;
HR/0: children at risk for ASD who showed no symptoms of ASD at 18 to 24 months;
HR/+: children with ASD who demonstrated some symptoms of ASD at the 18 -24 mo. (NB: not all HR/+ children met full criteria for ASD, some showed signs of a broader ASD phenotype).
Auditory Preference Procedure
A video monitor flashes a picture, calling the subject’s attention. When the child orients to the display, an auditory stimulus is played. The stimulus continues until the child turns away for at least two seconds, or until the entire trial is completed (15 seconds).
Child-directed (CD) speech vs. Adult-directed (AD) speech: Nursery rhymes were read twice each; once with “motherese” intonation and once with adult-directed intonation. Time spent orienting to the (CD) vs. (AD) samples was compared across diagnostic groups.
Lexical stress: Words with the English-dominant strong/weak stress pattern (MO ther) or the non-dominant weak/strong pattern (gui TAR) were read by an female speaker. Time orienting to the strong/weak vs. weak-strong samples were compared.
There were no differences among the groups in terms CD or AD speech; all children preferred CD. There were significant differences in preference for lexical stress patterns. The LR and HR/0 groups performed similarly; the HR/+ group preferences differed.
Children at risk for ASD show preferences for CD speech as typical peers do. However, HR children who show symptoms of ASD in their second year are less able to “tune in” to the details of English word structure during the first year of life, when templates for language acquisition are being established.