In a nutshell: People with autism tend to resist a sensory illusion called the “rubber hand illusion”, suggesting they draw less on contextual sensory information to make sense of the outside world.

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The big picture:

An authentic-looking, but clearly fake, plastic hand is placed in front of you. Your own hand is hidden under a cloth-covered table. Both hands are stroked repeatedly in the same spot. You have the unnerving sensation that you “own” the fake hand.

This is the rubber hand illusion. If you have access to a good prosthetic hand, you can try it at home.

In the lab, brain researchers use the rubber hand illusion to explore what our brains do when they receive conflicting information, and how our perception of the world around us affects how we move.

In the study reported here, people experiencing the rubber hand illusion were asked to reach for an object. Easy enough, you say. Not in this case: their movements were jerky as they overcame the illusion, and made the conscious decision to move their hidden real hand.

But adults with a diagnosis of autism were more resistant to the effects of the rubber hand illusion on their arm movement — their reaching movements were more sluggish overall, and didn’t show the typical jerkiness.

One interpretation of this finding is that people with autism pay less attention to contextual environmental cues — the sight of the lifelike rubber hand, seeing it being stroked, and so on — when processing sensory information, says lead author and PhD student Colin Palmer.

Palmer is a member of the Cognition and Philosophy Lab at Monash University, which is headed by CIBF’s Jakob Hohwy. The study was in collaboration with researchers at the Cognitive Neuroscience Unit at Deakin University, and the Monash Alfred Psychiatry research centre.

The team’s observation is reflected in other typical behaviours of people with autism. “Autistic individuals can tend to take things at face value, without considering a wider context,” says Palmer.

In social situations, most people interpret other people’s behaviour through cues that paint a picture of the context — for example subtle body language that indicates if a person is joking or being literal. However, people with autism often find it difficult to read social and emotional behaviour in others, sometimes leading to socially inappropriate behaviour and a perceived lack of empathy.

Next steps:
One possibility is to look at how visual cues about context affect interpretation of social situations in people with and without autistic traits.

Palmer, C. J., Paton, B., Kirkovski, M., Enticott, P. G., & Hohwy, J. (2015). Context sensitivity in action decreases along the autism spectrum: a predictive processing perspective. Proceedings of the Royal Society of London B: Biological Sciences, 282(1802), 20141557.

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