Categorical representation of facial expressions in the infant brain.
Categorical perception, demonstrated as reduced discrimination of within-category relative to between-category differences in stimuli, has been found in a variety of perceptual domains in adults. To examine the development of categorical perception in the domain of facial expression processing, we used behavioral and event-related potential (ERP) methods to assess discrimination of within-category (happy-happy) and between-category (happy-sad) differences in facial expressions in 7-month-old infants. Data from a visual paired-comparison test and recordings of attention-sensitive ERPs showed no discrimination of facial expressions in the within-category condition whereas reliable discrimination was observed in the between-category condition. The results also showed that face-sensitive ERPs over occipital-temporal scalp (P400) were attenuated in the within-category condition relative to the between-category condition, suggesting a potential neural basis for the reduced within-category sensitivity. Together, these results suggest that the neural systems underlying categorical representation of facial expressions emerge during the early stages of postnatal development, before acquisition of language.
Human Information Processing Laboratory, Department of Psychology, University of Tampere.
Jukka M
JM
Leppänen
Jenny
J
Richmond
Vanessa K
VK
Vogel-Farley
Margaret C
MC
Moulson
Charles A
CA
Nelson