May 19, 2000

A study in last week's issue of Nature finds that people with aphasia — a loss in language ability resulting from a stroke or other type of brain damage — appear to have a significant advantage in spotting liars, particularly when the untruths are given away by changes in facial expression. Nancy Etcoff, PhD, an MGH psychologist who led the study, explains that the phenomenon had been reported previously by neurologists treating people with aphasia but had never been studied in a scientific manner.

In the current study, Etcoff and her colleagues used a series of videotapes in which volunteers twice talked about their current emotional state in a positive way. In one instance they were looking at a pleasant scene and telling the truth, in the other instance they were looking at distressing scenes and lying about their emotional state. The tapes had been analyzed previously to identify subtle changes in facial expression or changes in vocal pitch associated with the untruthful interview.

The taped interviews were shown to a group of patients with aphasia and to three control groups. While people in general have only a 50/50 chance of detecting when someone is lying by their expression or tone of voice, the aphasia patients were able to detect lies cued by facial expression alone 73 percent of the time. The aphasia patients also did better than the other groups in detecting lies cued by both facial and vocal changes, but none of the groups did well in recognizing lies cued by changes in vocal pitch alone. Etcoff explains, "It looks like patients with aphasia may be more sensitive to nuances in facial expression that reveal a disconnect between what someone is trying to express and what they really are feeling."