Deaf signers outperform hearing non-signers in recognizing happy facial expressions.

The use of signs as a major means for communication affects other functions such as spatial processing. Intriguingly, this is true even for functions which are less obviously linked to language processing. Speakers using signs outperform non-signers in face recognition tasks, potentially as a result of a lifelong focus on the mouth region for speechreading. On this background, we hypothesized that the processing of emotional faces is altered in persons using mostly signs for communication (henceforth named deaf signers). While for the recognition of happiness the mouth region is more crucial, the eye region matters more for recognizing anger. Using morphed faces, we created facial composites in which either the upper or lower half of an emotional face was kept neutral while the other half varied in intensity of the expressed emotion, being either happy or angry. As expected, deaf signers were more accurate at recognizing happy faces than non-signers. The reverse effect was found for angry faces. These differences between groups were most pronounced for facial expressions of low intensities. We conclude that the lifelong focus on the mouth region in deaf signers leads to more sensitive processing of happy faces, especially when expressions are relatively subtle.