Abstract
Recent studies have suggested that adults' perception of facial identity and expression are not independent of one another. Facial expression aftereffects are dependent on facial identity in both adults (Fox & Barton, 2007) and children (Vida & Mondloch, 2009). In contrast, identity aftereffects in adult participants are independent of variation in facial expression (Fox et al., 2008), suggesting that adults' representation of facial identity is independent of expression. We examined whether identity aftereffects in 8-year-olds are modulated by changes in facial expression. In each of two experiments, children (n = 30) were shown an adapting face followed by a morphed blend between two identities. Adaptation significantly biased children's perception of the test identity away from the adapting identity, an effect that was independent of whether the morphed and adapting identities had the same or different emotional expressions. This indicates that, like adults, 8-year-olds process facial identity independent of expression. However, to be included in the above adaptation analyses, children were required to correctly categorize two facial identities at 100% identity strength and then at 80 and 90% identity strength across variations in expression. Approximately 33% of children were unable to pass training, despite the use of more distinctive faces and a more elaborate training procedure in Experiment 2. This suggests that there are individual differences in the extent to which 8-year-olds process identity independently of expression. In Experiment 3, we investigated these individual differences using a Garner interference task. Children categorized facial identities when expression was held constant (control trials) and when expression varied across trials (orthogonal trials). To date, data (n = 9) indicate that, unlike adults (Baudouin et al., 2008), 8-year-olds' reaction times are longer on orthogonal than control trials. Children's ability to process identity may be transitioning to an adult-like pattern at 8 years of age.