Enhanced neural sensitivity to brief changes of happy over angry facial expressions in preschoolers: A fast periodic visual stimulation study.

Across childhood, emotion perception from facial expressions has traditionally been studied with event-related potentials (ERP). Here, we explored the novel fast periodic visual stimulation (FPVS) electroencephalography (EEG) approach to provide information about how brief changes in facial expressions are processed implicitly in young children's brains. Utilizing two FPVS tasks for the first time in preschoolers, we examined brain responses to (1) the discrimination of brief changes in facial expressions at maximum intensity and (2) thresholds for discrimination of gradual increasing facial expression intensities. Within a stream of neutral faces at 6 Hz, happy and angry faces were embedded with a frequency of 1.2 Hz. Additionally, children performed an emotion recognition task (ERT). Data were collected in the context of a training study for socio-emotional competencies with typically developing children (N = 74; 5.1[0.9] years; 34 females). FPVS data were collected post-training, where training was included as a controlling factor. Across FPVS tasks, we detected robust expression change responses, particularly with larger responses for happy versus angry faces in the maximum intensity task. ERT results paralleled neural findings with faster reaction times and higher accuracy rates for happy versus angry faces. For gradual increases in emotional intensity, we found linear increases in responses across emotions. The majority of the sample showed a significant expression change at 60% intensity. With its implicit nature, short duration, and robustness of individual responses, our results highlight the potential of FPVS in comparison to classical ERP methods to study neural mechanisms of emotion perception in preschool samples.