Infants scan static and dynamic facial expressions differently

Abstract

How humans perceive facial expressions is an enduring question (see Darwin, 1873;Wundt, 1909). Using static stimuli such as the now-classic "Ekman faces" (Ekman & Friesen, 1976), much has been learned about its developmental trajectory. Infants can discriminate between certain static facial expressions from birth (Farroni et al., 2007;Field et al., 1982), and by seven months can identify many of the six "core" expressions (Ekman, 1993;Ekman et al., 1987) within discreet emotion categories (Kotsoni et al., 2001;Nelson et al., 1979;Ruba et al., 2017). Yet despite this advancement of knowledge, even the earliest studies have identified limitations of using static stimuli to investigate

Infants show pupil dilatory responses to happy and angry facial expressions

“…This prior work suggests that infants rapidly develop perceptual categories of emotion, and can categorise even highly similar facial configurations of the same valence and level of arousal (e.g., anger and disgust; Ruba et al, 2017). Infant eyetracking also suggests that even young infants show adult-like facial scanning Prunty et al, 2021;Soussignan et al, 2017), and look toward regions diagnostic for emotion recognition (see Jack et al, 2014;Smith et al, 2005). These studies, however, are not designed to determine if infants are receptive to the emotional content of facial configurations, or whether they are merely sensitive to differences in low-level perceptual information (see Barrett et al, 2019;Nelson, 1987).…”

“…Ekman & Friesen, 1976). Expression stimuli were validated by 51 adult observers (Prunty et al, 2021), and received high recognition accuracy scores (M = 84.57%, SD = 14.99%), and representativeness ratings (out of 5: M = 3.62, SD = .38). Discrete gaze-contingent boundaries for the eye region were defined individually for each face (all 6.8˚x 2.83˚).…”

“…Like previous work (Keemink et al, 2021), these age groups were selected to span this developmental period. We also included a static image condition to investigate the abovementioned role of dynamic-contingent displays (see Prunty et al, 2021;Wilcox & Clayton, 1968) on pupillary responses.…”

“…Previous work has established that infants are able to perceptually discriminate and categorise emotional expressions (Addabbo et al, 2018;Farroni et al, 2007;Keemink et al, 2019;Kotsoni et al, 2001;Nelson et al, 1979;Ruba et al, 2017;Safar et al, 2017). Evidence from eye-tracking paradigms has also shown that infants scan facial features in a similar way to adults; looking toward regions that are 'diagnostic' for decoding expressions (Hunnius et al, 2011;Keemink et al, 2021;Prunty et al, 2021;Soussignan et al, 2017). Yet how infants perceive facial expressions tells us little about whether or not they are receptive to the information communicated by expressive stimuli (Nelson, 1987;Ruba et al, 2019).…”

“…To increase real-world relevance, the six 'basic' expressions will be presented within brief social exchanges simulated using dynamic stimuli and gaze-contingent eye-tracking. This paradigm has been recently used to investigate infant scanning of emotional expressions (Keemink et al, 2021;Prunty et al, 2021) and similar gaze-contingent paradigms have also been used to study infant responsiveness within simulated interactions (Keemink et al, 2019;Vernetti et al, 2018), though not yet via pupillary response. Dynamism is increasingly being considered as a critical component of naturalistic stimuli in both adult (Richoz et al, 2018; see Krumhuber et al, 2013) and infant (Addabbo et al, 2018;Godard et al, 2016;Heck et al, 2016;Libertus et al, 2017;Soussignan et al, 2017)…”