Researchers in Boston used technology to measure empathy between psychotherapists and their patients.

"To our knowledge, this is the first study of the physiology of shared emotions during live psychotherapy sessions," said Carl Marci, the Harvard psychiatrist who led the study. "We were pleased to find evidence for a biological basis of empathic connections. Our results suggest that therapists perceived as being more empathic have more positive emotional experiences in common with patients."

Marci said research has shown that lack of empathy is the biggest predictor of a poor outcome for patients in psychotherapy. Still, empathy isn't everything, he said.

"Empathy is important, but it's not the whole story," Marci said. "It's not sufficient to determine the outcome of therapy."

In a study published in the February issue of the Journal of Nervous and Mental Disease, Merci and his colleagues described using a combination of skin sensors and videotapes viewed by neutral observers to measure empathy. They said their results suggest a nervous network for empathy and emotional response that is "implicated in the ability to take another's emotional perspective."