About 15 years ago, psychologist Geoff Bird began to question a long-held tenet in autism research: the idea that all autistic people struggle with empathy.For Bird, it just didn't make sense. In his experience, both autistic and non-autistic people vary widely in their ability to sense or feel another person's emotions -the scientific definition of empathy. And yet there was a body of research suggesting that autistic people are frequently unable to intuit what another person feels.Two of Bird's colleagues proposed a solution to the riddle: What if, instead of lacking empathy, some autistic people can't recognize their own emotions, a little-known trait called alexithymia? Wouldn't that impair their ability to share someone else's?Bird was skeptical but joined them on a research project -the results of which, published in 2010, shocked him: Among both autistic and non-autistic men, those with weaker brain responses to images of another person in pain had higher levels of alexithymia. After adjusting for alexithymiawhich was not routinely done -the empathetic brain responses in the two groups showed no differences at all. "I instantly thought, 'Wow,' and realized that this alexithymia hypothesis had the potential to be incredibly significant in autism," says Bird, professor of cognitive neuroscience at the University of Oxford in the United Kingdom.The 'alexithymia hypothesis,' if correct, may not only explain the broad range of emotionprocessing difficulties autistic people appear to have -including, sometimes, none. It could also shake up how autism is screened for, diagnosed, treated and even defined.Listen to a Spectrum webinar with Zachary Williams about measuring alexithymia.