Positive and negative facial emotional expressions: the effect on infants' and children's facial identity recognition

Aim of the present study was to investigate the origin and the development of the interdipendence between identity recognition and facial emotional expression processing, suggested by recent models on face processing (Calder & Young, 2005) and supported by outcomes on adults (e.g. Baudouin, Gilibert, Sansone, & Tiberghien, 2000; Schweinberger & Soukup, 1998). Particularly the effect of facial emotional expressions on infants’ and children’s ability to recognize identity of a face was explored. Studies on adults describe a different role of positive and negative emotional expressions on identity recognition (e.g. Lander & Metcalfe, 2007), i.e. positive expressions have a catalytic effect, increasing rating of familiarity of a face, conversely negative expression reduce familiarity judgments, producing an interference effect. Using respectively familiarization paradigm and a delayed two alternative forced-choice matching-to-sample task, 3-month-old infants (Experiment 1, 2, 3) and 4- and 5-year-old children (Experiment 4, 5) were tested. Results of Experiment 1 and 2 suggested an adult-like pattern at 3 months of age. Infants familiarized with a smiling face recognized the new identity in the test phase, but when they were shown with a woman’s face conveying negative expression, both anger or fear, they were not able to discriminate between the new and familiar face stimulus during the test. Moreover, evidence from Experiment 3 demonstrated that a single feature of a happy face (i.e. smiling mouth or “happy eyes”) is sufficient to drive the observed facilitator effect on identity recognition. Conversely, outcomes obtained in experiments with pre-school aged suggested that both positive and negative emotions have a distracting effect on children identity recognition. A decrement in children's performance was observed when faces 8 displayed an emotional expression (i.e. happiness, anger and fear) rather than a neutral expression (Experiment 4). This detrimental effect of a happy expression on face identity recognition emerged independently of the processing stage -i.e., encoding, recognition, encoding and recognition- at which emotional information was provided (Experiment 5). Overall, these findings suggest that, both in infancy and in childhood, facial emotional processing interacts with identity recognition. Moreover, observed outcomes seem to describe an U-shaped developmental trend of the relation between identity recognition and facial emotional expressions processing. The results are discussed by referring to Karmiloff-Smith’s Representational Redescription Model (1992).