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People with autism have trouble recognizing facial expressions and judging the emotional tone of spoken words — or at least, that’s what many researchers say. But some studies have found that not to be true.

The reason for these contradictory results could be that the studies tested the response to emotions of different types and intensity, says Ruth Grossman of the University of Massachusetts Medical School. Her team has found that kids with autism seem to have trouble only when identifying subtle, real-life emotions, rather than the gross exaggerations of fear or happiness that are rare in the real world.

To test this, as she explained at a poster session yesterday at the International Meeting for Autism Research in Chicago, Grossman designed a simple task.

She chose neutral, declarative sentences such as, “A friend asked me for help,” and hired actors to say them in happy, surprised, angry or sad tones of either high or low intensity. For high-intensity anger, for instance, the actors shouted the words, whereas for low-intensity anger, they spoke with only a tinge of annoyance.

Grossman played audio recordings to adolescents with autism and to healthy controls, and then asked, “Who said that?” The kids had to choose from two faces on a computer screen: one that matched the emotion in the voice and another that did not.

The two groups performed equally well with all the strong emotions — matching a shouting voice to a face with furrowed eyebrows, for example. Both groups did worse with milder emotions, but the autism group’s accuracy dropped much lower.

Based on these results, Grossman says studies should be designed to test a wider range of emotions. That seems especially wise for research on adults with autism, who have had years of experience reading faces. It would also be interesting to see whether, with explicit practice, these adults could learn how to read the less obvious expressions — a skill that can be tricky for any of us.