Attention to Conspecific Auditory Information in Infants at-Risk for Autism

Background:  In typical development, infants demonstrate perceptual biases that direct their attention to socially relevant, conspecific information (e.g., voices and faces of the same species; Johnson, Dziurawiec, Ellis, & Morton, 1991; Vouloumanos & Werker, 2004, 2007), which may facilitate infants’ ability to become competent linguistic and social beings (e.g., Tomasello, 2008; Werker & Curtin, 2005). For example, 3-month-olds prefer looking at human faces over gorilla and monkey faces (Heron-Delaney, Wirth, & Pascalis, 2011) and they prefer listening to human speech over nonspeech and rhesus monkey vocalizations (Shultz & Vouloumanos, 2010, Vouloumanos, et al., 2010). However, children diagnosed with Autism Spectrum Disorder (ASD) process auditory and visual information from conspecifics differently (Kuhl, et al., 2005; Chawarska, Volkmar, & Klin, 2010). Differences in these early biases could have cascading effects in development, suggesting that atypical conspecific biases in infancy may form the basis of the social communication difficulties characteristic of ASD (Surian & Siegal, 2008; Volkmar, Chawarska, & Klin, 2005). 

Objectives:  To examine whether 7 to 9-month-old infant siblings of children diagnosed with ASD (SIBS-A) attend to auditory conspecific information in the same way as infant siblings of typically developing children (SIBS-TD). Approximately 19% of SIBS-A will also be diagnosed with ASD by 3 years of age, thus representing a high-risk population of interest to researchers examining the early development of ASD (Ozonoff, et al., 2011).

Methods:  Infants were tested using the Infant-controlled Sequential Looking Preference Procedure (see Cooper & Aslin, 1990, 1994). The infants viewed 6 test trials consisting of 3 human speech (‘keev’, ‘ploo’, ‘boola’, etc.) and 3 monkey call (coos, girneys, warbles) trials paired with the static image of a bullseye on a monitor. Stimulus presentation was contingent on infants looking toward the monitor. We hypothesized that SIBS-TD would look longer to the human speech test trials and that SIBS-A would not differentially attend to either trial type.

Results:  We found a significant interaction between risk group status and attention to the human speech versus monkey calls, F(1, 63) = 4.16, p = .046. Follow-up comparisons revealed that SIBS-TD (n = 41) looked significantly longer during the monkey call trials (M = 19.75s, SD = 9.01) versus the human speech trials (M = 16.49s, SD = 9.16; t(1, 40)=2.77, p = .009); whereas SIBS-A (n = 24) did not demonstrate a clear preference for either stimulus (human: M = 17.71s, SD = 9.01; monkey: M = 17.27s, SD = 8.45; p = .729). 

Conclusions:  Our hypothesis was partially supported in that SIBS-A did not demonstrate a clear preference for either trial type, whereas SIBS-TD preferred the monkey calls. Stimulus preferences may shift during development such that younger infants prefer familiarity whereas older infants prefer novelty (Hunter & Ames, 1988). Compared with younger infants who prefer human speech over monkey calls (Vouloumanos et al., 2010), our results suggest a possible shift toward preferences for novelty by 7 to 9 months in TD infants in favour of monkey calls. These findings may have implications for the development of social communication.