It has been suggested that poor habituation to stimuli might explain atypical sensory behaviours in autism, i.e. over-responsiveness to some stimuli and under-sensitivity to other. We investigated habituation to repeated sounds using an oddball paradigm in 9 month-old infants with an older sibling with autism and hence at high risk for developing autism. Auditory evoked responses to repeated sounds in control infants (at low risk of developing autism) decreased over time, demonstrating habituation, and their responses to deviant sounds were larger than responses to standard sounds, indicating discrimination. In contrast, neural responses in infants at high risk showed no habituation, and reduced sensitivity to changes in frequency. Reduced sensory habituation may be present at a younger age than the emergence of autistic behaviour in some individuals, and we propose that this could play a role in the sensory atypicalities observed in autism
