A smile radiates outwards and biases the eye expression.

This study investigated how extrafoveally seen smiles influence the viewers' perception of non-happy eyes in a face. A smiling mouth appeared in composite faces with incongruent (angry, fearful, neutral, etc.) eyes, thus producing blended expressions, or they appeared in intact faces with genuine expressions. Overt attention to the eye region was spatially cued, foveal vision of the mouth was blocked by gaze-contingent masking, and the distance between the eyes and the mouth was varied. Participants evaluated whether the eyes were happy or not. Results indicated that the same non-happy eyes were more likely to be judged as happy, and more slowly to be judged as not happy, in presence more than in absence of a smile. As (a) the smiling mouth was highly salient regardless of type of eyes, (b) the influence on the eyes increased gradually as a function of eye-mouth proximity, and (c) the effect occurred in the absence of fixations on the mouth, we conclude that a salient smile radiates outwards to other face regions through a projection mechanism, thus making the eye expression look happy.