Infants show pupil dilatory responses to happy and angry facial expressions.

Facial expressions are one way in which infants and adults communicate emotion. Infants scan expressions similarly to adults, yet it remains unclear whether they are receptive to the affective information they convey. The current study investigates 6-, 9- and 12-month infants' (N = 146) pupillary responses to the six "basic" emotional expressions (happy, sad, surprise, fear, anger, and disgust). To do this we use dynamic stimuli and gaze-contingent eye-tracking to simulate brief interactive exchanges, alongside a static control condition. Infants' arousal responses were stronger for dynamic compared to static stimuli. And for dynamic stimuli we found that, compared to neutral, infants showed dilatory responses for happy and angry expressions only. Although previous work has shown infants can discriminate perceptually between facial expressions, our data suggest that sensitivity to the affective content of all six basic emotional expressions may not fully emerge until later in ontogeny.

Infants scan static and dynamic facial expressions differently.

Despite being inherently dynamic phenomena, much of our understanding of how infants attend and scan facial expressions is based on static face stimuli. Here we investigate how six-, nine-, and twelve-month infants allocate their visual attention toward dynamic-interactive videos of the six basic emotional expressions, and compare their responses with static images of the same stimuli. We find infants show clear differences in how they attend and scan dynamic and static expressions, looking longer toward the dynamic-face and lower-face regions. Infants across all age groups show differential interest in expressions, and show precise scanning of regions "diagnostic" for emotion recognition. These data also indicate that infants' attention toward dynamic expressions develops over the first year of life, including relative increases in interest and scanning precision toward some negative facial expressions (e.g., anger, fear, and disgust).

Eye Movements and Behavioural Responses to Gaze-Contingent Expressive Faces in Typically Developing Infants and Infant Siblings.

Studies with infant siblings of children with Autism Spectrum Disorder have attempted to identify early markers for the disorder and suggest that autistic symptoms emerge between 12 and 24 months of age. Yet, a reliable first-year marker remains elusive. We propose that in order to establish first-year manifestations of this inherently social disorder, we need to develop research methods that are sufficiently socially demanding and realistically interactive. Building on Keemink et al. [2019, Developmental Psychology, 55, 1362-1371], we employed a gaze-contingent eye-tracking paradigm in which infants could interact with face stimuli. Infants could elicit emotional expressions (happiness, sadness, surprise, fear, disgust, anger) from on-screen faces by engaging in eye contact. We collected eye-tracking data and video-recorded behavioural response data from 122 (64 male, 58 female) typically developing infants and 31 infant siblings (17 male, 14 female) aged 6-, 9- and 12-months old. All infants demonstrated a significant Expression by AOI interaction (F(10, 1470) = 10.003, P < 0.001, ŋp2  = 0.064). Infants' eye movements were "expression-specific" with infants distributing their fixations to AOIs differently per expression. Whereas eye movements provide no evidence of deviancies, behavioural response data show significant aberrancies in reciprocity for infant siblings. Infant siblings show reduced social responsiveness at the group level (F(1, 147) = 4.10, P = 0.042, ŋp2  = 0.028) and individual level (Fischer's Exact, P = 0.032). We conclude that the gaze-contingency paradigm provides a realistically interactive experience capable of detecting deviancies in social responsiveness early, and we discuss our results in relation to subsequent infant sibling development. LAY SUMMARY: We investigated how infant siblings of children with autism spectrum disorder respond to interactive faces presented on a computer screen. Our study demonstrates that infant siblings are less responsive when interacting with faces on a computer screen (e.g., they smile and imitate less) in comparison to infants without an older sibling with autism. Reduced responsiveness within social interaction could potentially have implications for how parents and carers interact with these infants. Autism Res 2021, 14: 973-983. © 2020 International Society for Autism Research and Wiley Periodicals LLC.

Caucasian Infants' Attentional Orienting to Own- and Other-Race Faces.

Infants show preferential attention toward faces and detect faces embedded within complex naturalistic scenes. Newborn infants are insensitive to race, but rapidly develop differential processing of own- and other-race faces. In the present study, we investigated the development of attentional orienting toward own- and other-race faces embedded within naturalistic scenes. Infants aged six-, nine- and twelve-months did not show differences in the speed of orienting to own- and other race faces, but other-race faces held infants' visual attention for longer. We also found a clear developmental progression in attentional capture and holding, with older infants orienting to faces faster and fixating them for longer. Results are interpreted within the context of the two-process model of face processing.

Infants' responses to interactive gaze-contingent faces in a novel and naturalistic eye-tracking paradigm.

Face scanning is an important skill that takes place in a highly interactive context embedded within social interaction. However, previous research has studied face scanning using noninteractive stimuli. We aimed to study face scanning and social interaction in infancy in a more ecologically valid way by providing infants with a naturalistic and socially engaging experience. We developed a novel gaze-contingent eye-tracking paradigm in which infants could interact with face stimuli. Responses (socially engaging/socially disengaging) from faces were contingent on infants' eye movements. We collected eye-tracking and behavioral data of 162 (79 male, 83 female) 6-, 9- and 12-month-old infants. All infants showed a clear preference for looking at the eyes relative to the mouth. Contingency was learned implicitly, and infants were more likely to show behavioral responses (e.g., smiling, pointing) when receiving socially engaging responses. Infants' responses were also more often congruent with the actors' responses. Additionally, our large sample allowed us to look at the ranges of behavior on our task, and we identified a small number of infants who displayed deviant behaviors. We discuss these findings in relation to data collected from a small sample (N = 11) of infants considered to be at-risk for autism spectrum disorders. Our results demonstrate the versatility of the gaze-contingency eye-tracking paradigm, allowing for a more nuanced and complex investigation of face scanning as it happens in real-life interaction. As we provide additional measures of contingency learning and reciprocity, our task holds the potential to investigate atypical neurodevelopment within the first year of life. (PsycINFO Database Record (c) 2019 APA, all rights reserved).