Autism impedes ability to read body language

A glitch in visual processing may explain why people with autism struggle to gauge emotions from the body language of others, according to a study published in the journal Neuropsychologia¹.

The problem may stem from the fact that people with autism tend to focus on small, local details of body movement — such as the activity of one hand — rather than the motion of a body as a whole, says study investigator Anthony Atkinson, lecturer in psychology at Durham University, UK. That would explain why people with the disorder have trouble gleaning implicit emotional meaning from specific movements or postures.

Scientists have long known that people with autism struggle to discern emotions from other types of social signals, such as the facial expressions² or voices³ of others.

The new findings, published online in June, indicate that body language is another important cue that’s misread by people with the disorder — and one that could be a target for future behavioral interventions.

“Given the important role that assessing other people’s feelings has on everyday interactions, and given that difficulties of social interaction are one of the diagnoses of autism, it might help if we could develop training techniques that help them pick up on [movement] cues that we look at to judge others’ emotional states,” Atkinson says.

What might be most effective, he adds, is a therapy with two parts. First, it would teach people with autism important cues for perceiving emotion — that a shaking fist denotes anger, for instance. Second, it would train them to view larger areas of another person’s body through repetitive exercises, instead of zooming in on local details.

Drifting snowflakes:

Although scientists have conducted hundreds of studies exploring face and voice perception in people with autism, the first study to probe their understanding of body language did not appear until 1997⁴ and only a handful of studies have followed since.

In the new work, Atkinson conducted two separate tests on 13 adults diagnosed with high-functioning autism or Asperger syndrome, and 16 healthy controls. In the first test, he presented the participants with two sets of three-second video clips showing actors using explicit movements to act out different emotions, including anger, fear, disgust, sadness and happiness. For example, an actor portraying happiness is jumping up and down.

In one set of clips, the actor’s face is blurred but the rest of the body is visible. In the second set, the actor’s body is replaced with moving white dots, each corresponding to a different joint. These ‘point-light’ animations allow researchers to assess how well participants read body language in the absence of form.

When watching either type of clip, people with autism are consistently less accurate than are controls in judging emotions conveyed by the actors’ movements.

The second part of the study found that participants who struggle most with the video exercise also fare worst at perceiving ‘coherent motion’. Like snowflakes blowing in a breeze, coherent motion describes the movement of spatially separate elements in which most, but not all, are moving in the same direction.

In this test, Atkinson shows participants a cloud of dots on a computer screen and asks which way the dots are moving. A proportion of dots move noticeably to the left or right, while others move randomly.

The test has different difficulty levels depending on the percentage of dots moving in one direction. Most healthy participants can gauge the direction of the cloud even when just 35 to 40 percent of the dots are moving in one direction, the study found.

In contrast, at least 75 percent of the dots must be coherently moving together before most people with autism can correctly determine the direction. This is probably because they focus on just a few dots, rather than taking in their cumulative motion, says Atkinson.

The fact that participants with autism tend to perform poorly on both tasks suggests that their ability to judge emotions from body language depends on the ability to perceive motion over a larger area of the body, he adds.

Probing the brain:

But that may not be the whole explanation, as a few studies have found that some people with autism process coherent motion just as well as healthy controls^5,6, says Chantal Kemner, professor of child and adolescent psychiatry at University Medical Center Utrecht, The Netherlands.

Rather, an anomaly in the way people with autism process ‘spatial frequencies’, or the various types of visual information within an object, could have something to do with their struggle to derive emotional meaning from other people’s faces or motions, Kemner says.

High spatial frequencies represent sharp edges and fine perceptual details, whereas low spatial frequencies describe the shapes and contours of objects. Studies suggest that people with autism preferentially use high spatial frequencies to process faces⁷, which means they may be missing out on other crucial visual information, she says.

Regardless of the mechanism behind the deficits in reading body language, “this study is more evidence that, despite some data to the contrary, combining motion information across space is problematic even for high-functioning autism populations,” says David Simmons, a lecturer in psychology at the University of Glasgow.

What’s important to investigate next is exactly how the brain processes ‘social’ content — such as emotions and physical appearance — in others’ movements, Simmons adds.

So far, brain imaging studies have pointed to one brain region that is likely to be involved: the superior temporal sulcus, located in the middle of the brain. The region is active when perceiving others’ movements and judging their mental states.

“The superior temporal sulcus is the suspect of the day,” says Frank Pollick, professor of psychology at the University of Glasgow and an expert on the perception of motion.

Despite the importance of assessing the role of body language in the day-to-day interactions of people with autism, Pollick says it’s also important to remember that body language is just one of several social cues that influences the perception of others’ emotions.

“The logical next step is trying to integrate things to look at movements, the face, the voice and sounds, and think about how the sum of all those parts contributes to the overall perception of [other people’s feelings].”