Abstract
Sensitive responding to eye cues plays a key role during human social interactions. Observed changes in pupillary size provide a range of socially-relevant information including cues regarding a person’s emotional and arousal states. Recently, infants have been found to mimic observed pupillary changes in others, instantiating a foundational mechanism for eye-based social communication. Among adults, perception of pupillary changes is affected by race. Here, we examined whether and how race impacts the neural processing of others’ pupillary changes in early ontogeny. We measured 9-month-old infants’ brain responses to dilating and constricting pupils in the context of viewing own-race and other-race eyes using functional near-infrared spectroscopy (fNIRS). Our results show that only when responding to own-race eyes, infants’ brains distinguished between changes in pupillary size. Specifically, infants showed enhanced responses in the right superior temporal cortex when observing own-race pupil dilation. Moreover, when processing other-race pupillary changes, infants recruited the dorsolateral prefrontal cortex, a brain region linked to cognitive control functions. These findings suggest that, early in development, the fundamental process of responding to pupillary changes is impacted by race and interracial interactions may afford greater cognitive control or effort. This critically informs our understanding of the early origins of responding to pupillary signals in others and further highlights the impact of race on the processing of social signals.
Highlights
The ability to detect and respond to information from the eyes is an early developing capacity that is considered a foundational feature of human social cognition in infancy[1,2]
Considering that changes in pupil size are closely tied to changes in physiological arousal controlled by the autonomic nervous system, it is possible that the coordination of arousal between social partners facilitates pupil mimicry or alternatively that pupil mimicry facilitates the unconscious coordination of arousal between social partners[6,7,8,9,10]
On the basis of the abovementioned studies examining the neural correlates of processing pupillary changes in adults and given the neural sensitivity to dynamic eye gaze and emotional cues in the superior temporal cortex previously demonstrated in infants[20,22,23], we hypothesized that observed changes in pupil size will result in differential brain responses in infants’ superior temporal cortex (STC)
Summary
The ability to detect and respond to information from the eyes is an early developing capacity that is considered a foundational feature of human social cognition in infancy[1,2]. Prior work with adults using functional magnetic resonance imaging (fMRI) shows that the right superior temporal sulcus, a region implicated in processing a wide array of dynamic social information from faces, including emotional and gaze cues[17], responds to changes in pupil size[18,19]. In this context, it is important to emphasize that, similar to adults, there is evidence from previous studies with infants showing that the superior temporal cortex, especially in the right hemisphere, is involved in eye gaze and emotion processing from early in infancy[20,21]. Considering the lateralization of STC responses reported in infants and adults[20,21,24], we decided to test for brain response lateralization by including hemisphere (left and right) as a factor in our fNIRS analyses
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