Infants at Risk for ASD Show Aberrant Preferences for Speech Stimuli at 6 and 9 Months

Background:

The role played by genetic factors in the incidence of ASD has led to studies of infants siblings of children with ASD, in order to identify earliest-appearing symptoms of the disorders, with the aim of potential early identification. 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 (McRoberts, et al., 2009) has demonstrated that preferences for listening to speech-like sounds change at about 6 months from those based on prosody to those more focused on content.

Objectives:

This study examines differences in preferences for child-directed speech in infants at high and low risk for ASD at 6 and 9 months of age.

Methods:

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. The present report examines data from the 6 and 9 month visits of HR and LR children. Groups were matched for nonverbal developmental level.

Auditory Preference Procedure. The infants sat on their parent’s lap before a video monitor with a speaker below it.  The monitor flashed a picture, calling the subject’s attention. When the child oriented to the display, an auditory stimulus was played, and continued until the child turned away for at least two seconds, or until the entire trial was completed (15 seconds).

Stimuli. Child-directed (CD) speech vs. Adult-directed (AD) speech: Nursery rhymes were read twice each; once with “motherese” prosody and once with adult-directed prosody. Time spent orienting to the CD vs. AD samples was compared across diagnostic groups.

Results:

 In the LR group, there was no evidence of a preference for speech with CD prosody at 6 mo., but there was a preference at 9 mo. This pattern replicates findings for TD children in McRoberts et al., (2009), which indicated that at 6 months infants do not prefer CD based on its prosodic character, but only when it contains high levels of repetition of content words, and return to preferring speech with motherese prosody at 9 months, when structural properties of language input become relevant. For the HR group, this pattern seen in typical infants was reversed; that is, a preference for CDS at 6 months, but not at 9 months.

Conclusions:

Infants at risk for ASD show a different pattern of preferences for CD speech when compared to LR peers. We will argue that this pattern represents a delay on the part of the HR infants, and is congruent with delays in vocal production reported in the literature at the same point in development. The implications of these delays for language acquisition will be discussed.

 

McRoberts, G.W., McDonnough, C., & Lukusta, L. (2009). The Role of Verbal Repetition in the Development of Infant Speech Preferences From 4 to 14 Months of Age. Infancy, 14(2), 162-194.