The developmental time course and topographic distribution of individual-level monkey face discrimination in the...

The ability to discriminate between faces from unfamiliar face groups has previously been found to decrease across the first year of life. Here, individual-level discrimination of faces within a previously unfamiliar group was investigated by measuring neural responses to monkey faces. Six- and 9-month-old infants (n = 42) completed a Fast Periodic Visual Stimulation (FPVS) task while steady state visual evoked potentials (ssVEPs) were recorded. Using an oddball task design (e.g., infrequent changes in face identity) faces were presented at a 6Hz (1 face approximately every 167ms) stimulation rate and every 1.2Hz different individual monkey faces were presented. Significant SNRs at 1.2Hz in both 6- and 9-month-old infants suggest that neural responses, recorded over posterior scalp regions, remain sensitive to individual-level differences within an unfamiliar face group despite previous behavioral evidence of decreased discrimination. However, the topographic distribution of the 1.2Hz response varied by age, suggesting that 6- and 9-month-old infants are using different neural populations to discriminate unfamiliar faces at the individual level.