Categorical Representation of Facial Expressions in the Infant Brain

Abstract

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.

Categorical perception of emotional facial expressions in preschoolers

“…They found that both groups showed categorical perception for the continua they tested and that early experience of abuse changed identification of the angry expression (i.e., it was overidentified). Leppänen, Richmond, Vogel-Farley, Moulson, and Nelson (2009) found that infants presented with within-and between-category expressions (happy and sad) showed increased looking time in a visual preference task to between-category pairings but not to within-category pairings. Furthermore, they found that event-related potentials differed depending on condition, that is, between or within category.…”

Developmental changes in infants’ categorization of anger and disgust facial expressions.

“…However, this is extremely unlikely given that infants younger than 10 months are sensitive to identity and emotion information with across-valence expressions (e.g., Kahana-Kalman & Walker-Andrews, 2001;Schwarzer & Jovanovic, 2010). An alternative possibility is that within-valence expressions, such as anger and disgust, require additional cognitive resources to process (Leppänen et al, 2009) because they carry additional informational value (Peeters & Czapinski, 1990). For infants, this additional information may elicit greater attention and increase cognitive demands (Vaish, Woodward, & Grossmann, 2008).…”

“…Only a few studies have explored infants' ability to discriminate within-valence, negative expressions such as fear and sadness (Parker & Nelson, 2005) or anger and sadness (Schwartz, Izard, & Ansul, 1985). These facial expressions are perceptually and conceptually similar, making discrimination and categorization tasks challenging (Leppänen, Richmond, Vogel-Farley, Moulson, & Nelson, 2009). Thus, a lack of empirical attention in this area is problematic, considering that four basic-level emotions (Ekman, 1972) are negatively valenced (i.e., sadness, anger, disgust, fear).…”

Categorical perception along the happy–angry and happy–sad continua in the first year of life

“…Leppänen, Richmond, Vogel-Farley, Moulson, and Nelson (2009) found that in a visual preference task with happy and sad expressions, infants showed increased looking time to the between category pairings but not to within category pairings. Sevenmonth-old infants show evidence of categorical perception along the happy-fear continuum, but only when habituated to a happy face rather than to the fear face (Kotsoni, de Haan, & Johnson, 2001).…”