Scientific Method / Science & Exploration

Autistic toddlers aren’t interested in biological movement

Researchers show that the lack of interest in biological movement is already …

Autism can be a debilitating condition that has serious consequences for both those suffering from it and their families. What really distinguishes autism spectrum disorder (ASD) from other problems is the way that those with the disorder interact socially. Social issues, apart from being one of its symptoms, also make those with ASD more challenging to interact with.

One notable example of social interaction deficits involves the ability to recognize "biological movement." It turns out that, from a very young age, most people can distinguish movements associated with living things. But autistic people have difficulty distinguishing biological movement from the random movements of nonliving objects, a property they don't share with those suffering from other behavioral disorders. As a result, their attentive gaze seems to randomly focus on things. Now, with a little bit of luck, researchers have discovered a clue as to the attentional cues that attract autistic people.

To try and explore if this behavior was present in pre-lingual toddlers with autism, researchers put together a set of movies that used biological movements, but skipped the biology. These animations showed points of light playing games like pat-a-cake, complete with a soundtrack. In control animations, the same movies were played backwards but with the soundtrack still playing forwards. This had the effect of making the motion appear non-biological.

The authors played these movies to three groups of two year olds and tracked their attention by monitoring the direction of their gaze. One group was considered to be developmentally normal, while a second control group was developmentally delayed but not autistic. These two groups paid considerably more attention to the biological videos, while a third group, which consisted of children diagnosed with autism, had attention that was distributed randomly.

That finding is important in itself, but in analyzing the data, the researchers discovered an outlier. One particular autistic child paid far more attention to one particular biological movement video—in fact, she spent 90 percent of her time watching the pat-a-cake move. Upon closer analysis, all the autistic children paid significantly more attention to pat-a-cake. 

The researchers decided that there must be something special about that particular set of actions. Inspecting their animations, they noticed that the pat-a-cake video had a very high correlation between the movement of the points of light and the soundtrack—specifically, the hands of the figure clapping together at the same time as the clapping noise.

The researchers then proceeded to analyze the rest of their animations for correlations between the animated figure's movement and the soundtrack. They then used this information to re-analyze the gaze statistics of the three groups of toddlers. They found that the synchronization made very little difference to the two control groups—biological movement was still heavily favored. The autistic group, however, showed a strong preference for watching highly correlated animations.

This preference for correlations between senses may go some way towards explaining why autistic people seem to prefer to watch a speaker's mouth rather than their eyes. It also shows that the biological movement deficit is already present in two year olds with autism.

There is also a danger of over-interpreting the data though. For instance, my first thought was that this research could be used to provide an early diagnosis of autism, allowing for an earlier transition to appropriate care regimes. But, on reflection, I doubt that this would work, because early childhood development does not proceed on a fixed schedule, making it very easy to use one particular facet of autism to misdiagnose large numbers of children.

Nevertheless, there is potential that this particular deficit—the inability to recognize biological movement—may explain a wide range of behaviors and, perhaps, be linked to the development of particular neural circuits. This might be used in the future to explain how genetic factors come together with environmental factors to cause ASD.

Nature, 2009, DOI: 10.1038/nature07868

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