Brain perks up to uncertain threats

The brain shows particular sensitivity to facial expressions that convey ambiguous threats rather than clear ones, according to a new brain-imaging investigation.

In their study, Reginald B. Adams Jr. of Dartmouth College in Hanover, N.H., and his coworkers assumed that an angry facial expression indicates a clear threat to an observer if it’s combined with eyes looking straight ahead, but an ambiguous threat if combined with eyes looking away.