The effect of emotional expression on age estimates is modulated by face age and participant age.

Observers can infer a person's age from the face, but not perfectly, and emotional expressions have been shown to affect these judgments. However, the effect of expressions on age perception is still not well understood. In this study, we first asked young Asian participants to estimate the age of young, middle-aged, and older White faces, showing neutral, happy, and angry expressions (Experiment 1), and additionally recruited young and older Asian participants to estimate both White and Asian faces (Experiment 2), to examine how face age and participant age modulate the emotional effects on age estimates. The results replicated previous findings that happy faces were perceived as older than neutral faces when faces were young. The aging effect of angry expressions was also found in young faces. Importantly, the strength that happy and angry expressions make young faces look older was larger as participants became older. Interestingly, the aging effect of expressions was also larger in the other-race (i.e., White) than the own-race (i.e., Asian) faces. When faces were older, smiling did not age the faces, regardless of participant age or face race. Our results suggest that the transient aging cues brought by facial expressions, like the smile or frown-related wrinkles, seemed to be weighted differently during age estimation, depending on both the characteristics of faces and observers.