Despite the distractions of various ill-informed advocates, scientific research into the causes and symptoms of autism continues to turn up fresh information. One of the more active research areas involves trying to understand how changes in the brain structure and function in those with autism translate into observed deficits.

For instance, autistic people sometimes have difficulty inferring intent from physical action. So, for instance, if you reach for a cup of coffee, most people, including those with autism, will correctly assume that you are going to take hold of the cup. However, autistic people may have difficulty determining if you are reaching for the cup to take a drink or to simply move the cup, while the rest of us can usually correctly infer this information. A study, published in PLoS One, has provided some evidence that makes it likely that this particular deficit is due to a specific brain function that's not doing its job properly.

First, let's provide some context. This study involved showing pictures of people reaching for objects to groups of developmentally normal and autistic children. The children had to identify the object, the motor action (e.g., to grasp) and the intent of the action. The photographs also controlled for context—some photos had additional clues from which intent could be inferred, while others did not.

This is not the first study of its kind, but the existing studies provide contradictory results. Some earlier studies showed that autistic people identify intent as well as normal people, while others showed that there is a deficit. Coupled with what we know of the physiology of the brain, this is a bit confusing, because we know the structures involved in inferring intent and that this particular part of the brain doesn't work very well in autistic people.

How do we infer intent? Intent is thought to be primarily derived from what are called mirror neurons. When you move your arm to pick up a coffee cup, your motor neurons control the arm motion. As an observer, I have a set of neurons that mirror this action in my brain, firing as if I were also controlling your arm.

These neurons are divided into two sets. The first is a single neuron that fires in response to the actual motion; this firing then triggers a secondary train of neurons that derive intent based on our own previous experience. In autistic people, this first neuron functions normally, but the following chain is highly disrupted. If that's the case, the researchers wondered, why were previous study results so mixed?

Their hypothesis was that, given the failure of the second mirror neuron train, perhaps autistic people relied heavily on other cues that previous studies had not controlled for. The researchers designed a series of tests that allowed for them to distinguish when intent could be inferred from context and when it could only be inferred through the process that happens downstream of the mirror neurons.

They found that, as predicted by their hypothesis, when intent could be inferred from context, autistic children performed as well as their control partners in identifying it. However, once that context was removed, autistics were worse at identifying intent.

This study taken by itself doesn't show much but, viewed in the context of physiology and previous studies, may provide a good explanation of how autistic people identify intent. It also strengthens the conclusions derived from studies of mirror neurons. Less directly, it highlights the flexibility of the brain: identifying intent is a key process in understanding the world around us, and the brain may have a preferred mechanism for doing this, but it is also flexible enough to develop other methods to compensate when the primary one fails.

PLoS One, DOI: 10.1371/journal.pone.0005596