Abstract
Emotional facial expressions provide a useful indicator of others' affective states. Adults perceive blends of facial expressions categorically (i.e., separated by a clear boundary) and dynamically; an ambiguous expression is perceived as sad following adaptation to a happy expression, but as happy following adaptation to sad. These expression aftereffects are strong when the adapting and probe expressions share the same facial identity, but are mitigated when they are posed by different identities, indicating that adults' perception of facial expression is integrated with identity (Fox & Barton, 2007). In Experiment 1, we extended these findings by comparing categorical boundaries and expression aftereffects in adults versus children (n = 20 per group). We created two morphed continua of facial expressions (happy-sad, fear-anger) in which contiguous faces differed by 5%. Participants classified each face in one of the two continua in three blocks of trials: no-adaptation, same-identity adaptation and different-identity adaptation. For the happy-sad continuum, both 5- and 7-year-olds showed adult-like category boundaries. All groups showed significant aftereffects in the same-identity condition, but the effects were larger for 5-year-olds (p p p p [[lt]].01), indicating that expression and identity may be less well integrated for other-race faces than own-race faces.