Understanding others and being understood in turn is something that most of us take for granted. Development of this capacity for effective communication requires attention to social stimuli, including speech and body language. People with autism orient poorly to social stimuli, showing a distinct attentional preference for objects over people. This abnormal orientation contributes to the impairment of language that is a hallmark of this increasingly prevalent developmental disorder.

As socially meaningful cues are physically complex, it has been hypothesized that subjects with autism might have difficulty encoding and representing sensory information. As reported in Proceedings of the National Academy of Sciences, C̆eponienė and colleagues tested this hypothesis in high-functioning children with autism.

Event-related brain potentials were recorded during presentation of acoustically matched tones and vowels, to compare responses to non-speech and speech sounds, respectively. Presenting these acoustic stimuli as an 'oddball' sequence in which a 'deviant' sound was occasionally substituted for a 'standard' repetitive sound allowed the researchers to discriminate between sensory processing and involuntary attentional orienting.

Surprisingly, test subjects with autism showed no significant abnormalities in sensory processing of either tones or vowels. By contrast, their attentional orienting to deviant sounds was impaired. Interestingly, this impairment was selective for vowel sounds — attentional switching was normal in response to deviant non-speech tones, regardless of their complexity. These results indicate that the impairment of auditory processing that inhibits language development in people with autism lies downstream of sensory processing.