Emergence of Neural Face Selectivity in Infants Younger Than 4 Months Old

TL;DR

This study shows that infants under 4 months old can show face-selective brain responses when presented with specially designed, more salient visual stimuli.

Contribution

The study introduces a new stimulus set that reveals earlier emergence of face-selectivity in infants than previously observed.

Findings

Infants as young as 2 months showed face-selective responses only to the new, more salient stimulus set.

The new stimulus design improved face-selectivity detection in rapid visual presentations for infants.

Face-selectivity in infants was observed at 1 Hz in the EEG spectrum using the new stimulus set.

Abstract

Research on face‐selectivity in infants under 4 months has shown mixed results, especially with rapid stimulus presentations. Here we tested whether increasing face saliency would promote face‐selective responses even with brief presentation times in infants aged 4‐to‐6 months and younger. Using frequency‐tagging EEG, we presented face and nonface stimuli at a rapid 6‐Hz rate (i.e., 167 ms/stimulus), with faces appearing once per second as every 6th stimulus, therefore isolating face‐selectivity at 1 Hz in the EEG spectrum. Two sets of images were presented in separate conditions: a “classic” set from previous studies and a “new” more salient set with increased luminance and size of the depicted items as well as a smoother background intending to facilitate figure‐ground segregation. In Experiment 1, we validated the use of the new set to elicit high‐level face‐selectivity in adults (N = 19). Crucially, Experiment 2 demonstrated benefits from the new set for 2‐to‐6‐month old infants (N = 46), with the youngest ones (2‐to‐4‐month‐olds) featuring face‐selective responses only to this new set. Thus, adapting stimuli to the visual capabilities of infants uncovered earlier developmental emergence of face‐selectivity to rapid visual stimulation than previously thought.

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