Age, not Autism, Influences Multisensory Integration of Speech Stimuli
Differences between autistic and non-autistic individuals in perception
of the temporal relationships between sights and sounds are theorized to
underlie difficulties in integrating relevant sensory information.
These, in turn, are thought to contribute to problems with speech
perception and higher level social behaviors. However, the literature
establishing this connection often involves limited sample sizes and
focuses almost entirely on children. To determine whether these
differences persist into adulthood, we compared 469 autistic and 373
non-autistic adults (aged 17 to 75 years). Participants completed an
online version of the McGurk/MacDonald paradigm, a multisensory illusion
indicative of the ability to integrate audiovisual speech stimuli.
Audiovisual asynchrony was manipulated, and participants responded both
to the syllable they perceived (revealing their susceptibility to the
illusion) and to whether or not the audio and video were synchronized
(allowing insight into temporal processing). In contrast with prior
research with smaller, younger samples, we detected no evidence of
impaired temporal or multisensory processing in autistic adults.
Instead, we found that in both groups, multisensory integration
correlated strongly with age. This contradicts prior presumptions that
differences in multisensory perception persist and even increase in
magnitude over the lifespan of autistic individuals. It also suggests
that the compensatory role multisensory integration may play as the
individual senses decline with age is intact. These findings challenge
existing theories and provide an optimistic perspective on autistic
development. They also underline the importance of expanding autism
research to better reflect the age range of the autistic population.