Face Processing in Early Development: A Systematic Review of Behavioral Studies and Considerations in Times of COVID-19 Pandemic

Exploring the impact of parents' face-mask wearing on dyadic interactions in infants at higher likelihood for autism compared with general population

Since the COVID-19 pandemic, both the public and researchers have raised questions regarding the potential impact of protective face-mask wearing on infants' development. Nevertheless, limited research has tested infants' response to protective face-mask wearing adults in real-life interactions and in neurodiverse populations. In addition, scarce attention was given to changes in interactive behavior of adults wearing a protective face-mask. The aims of the current study were (1) to examine differences in 12-month-old infants' behavioral response to an interactive parent wearing a protective face-mask during face-to-face interaction, (2) to investigate potential differences in infants at higher likelihood for autism (HL-ASD) as compared with general population (GP) counterparts, and (3) to explore significant differences in parents' behaviors while wearing or not wearing a protective face-mask. A total of 50 mother-infant dyads, consisting of 20 HL-ASD infants (siblings of individuals with autism) and 30 GP infants, participated in a 6-min face-to-face interaction. The interaction was videotaped through teleconferencing and comprised three 2-min episodes: (a) no mask, (b) mask, and (c) post-mask. Infants' emotionality and gaze direction, as well as mothers' vocal production and touching behaviors, were coded micro-analytically. Globally, GP infants exhibited more positive emotionality compared with their HL-ASD counterparts. Infants' negative emotionality and gaze avoidance did not differ statistically across episodes. Both groups of infants displayed a significant increase in looking time toward the caregiver during the mask episode. No statistically significant differences emerged in mothers' behaviors. These findings suggest that the use of protective face-masks might not negatively affect core dimensions of caregiver-infant interactions in GP and HL-ASD 12-month-old infants.

Asymmetries in event-related potentials part 1: A systematic review of face processing studies

The human brain shows distinct lateralized activation patterns for a range of cognitive processes. One such function, which is thought to be lateralized to the right hemisphere (RH), is human face processing. Its importance for social communication and interaction has led to a plethora of studies investigating face processing in health and disease. Temporally highly resolved methods, like event-related potentials (ERPs), allow for a detailed characterization of different processing stages and their specific lateralization patterns. This systematic review aimed at disentangling some of the contradictory findings regarding the RH specialization in face processing focusing on ERP research in healthy participants. Two databases were searched for studies that investigated left and right electrodes while participants viewed (mostly neutral) facial stimuli. The included studies used a variety of different tasks, which ranged from passive viewing to memorizing faces. The final data selection highlights, that strongest lateralization to the RH was found for the N170, especially for right-handed young male participants. Left-handed, female, and older participants showed less consistent lateralization patterns. Other ERP components like the P1, P2, N2, P3, and the N400 were overall less clearly lateralized. The current review highlights that many of the assumed lateralization patterns are less clear than previously thought and that the variety of stimuli, tasks, and EEG setups used, might contribute to the ambiguous findings.

Neuroadaptive Bayesian optimisation to study individual differences in infants' engagement with social cues

Infants' motivation to engage with the social world depends on the interplay between individual brain's characteristics and previous exposure to social cues such as the parent's smile or eye contact. Different hypotheses about why specific combinations of emotional expressions and gaze direction engage children have been tested with group-level approaches rather than focusing on individual differences in the social brain development. Here, a novel Artificial Intelligence-enhanced brain-imaging approach, Neuroadaptive Bayesian Optimisation (NBO), was applied to infant electro-encephalography (EEG) to understand how selected neural signals encode social cues in individual infants. EEG data from 42 6- to 9-month-old infants looking at images of their parent's face were analysed in real-time and used by a Bayesian Optimisation algorithm to identify which combination of the parent's gaze/head direction and emotional expression produces the strongest brain activation in the child. This individualised approach supported the theory that the infant's brain is maximally engaged by communicative cues with a negative valence (angry faces with direct gaze). Infants attending preferentially to faces with direct gaze had increased positive affectivity and decreased negative affectivity. This work confirmed that infants' attentional preferences for social cues are heterogeneous and shows the NBO's potential to study diversity in neurodevelopmental trajectories.

Lesson learned from the COVID-19 pandemic: toddlers learn earlier to read emotions with face masks

In a prior study we demonstrated that the presence of face masks impairs the human capability of accurately inferring emotions conveyed through facial expressions, at all ages. The degree of impairment posed by face covering was notably more pronounced in children aged between three and five years old. In the current study, we conducted the same test as a follow-up after one year from the onset of the COVID-19 pandemic, when the requirement of wearing face masks was holding in almost all circumstances of everyday life when social interactions occur. The results indicate a noteworthy improvement in recognizing facial expressions with face masks among children aged three to five, compared to the pre-pandemic settings. These findings hold a significant importance, suggesting that toddlers effectively mitigated the social challenges associated with masks use: they overcame initial environmental limitations, improving their capability to interpret facial expressions even in the absence of visual cues from the lower part of the face.

Antenatal and neonatal exposure to SARS-CoV-2 and children's development: a systematic review and meta-analysis

OBJECTIVES

To conduct a systematic review of the impact of antenatal and neonatal exposure to SARS-CoV-2 on developmental outcomes in preterm and term-born infants.

METHODS

We searched Embase, Emcare, MEDLINE, PsycINFO, Web of Science and grey literature on May 27, 2022 and updated on May 8, 2023. Studies defining exposure with a positive SARS-CoV-2 protein or genetic material, used a contemporaneous non-exposed cohort, and reported developmental outcomes up to 2 years of age were included.

RESULTS

Four out of 828 screened studies were included. Meta-analysis included 815 infants screened for developmental delay (n = 306 exposed; n = 509 non-exposed) between 3- and 11-months of age. Among term-born infants, we did not find an increased risk of delay in communication (odd's ratio: 0.73 (95% CI: 0.24-2.24)), gross motor (1.50 (0.62, 3.62)), fine motor (2.90 (0.58, 14.43)), problem-solving (1.19 (0.54, 2.66)) or personal-social development (1.93 (0.78, 4.75)) in exposed infants. The number of preterm-born infants in the exposed (n = 37) and comparison cohorts (n = 41) were too few to report meaningful comparisons.

CONCLUSION

Evidence regarding the potential impact of antenatal or neonatal exposure to SARS-CoV-2 infection on developmental outcomes in early infancy is limited and inconsistent. Larger cohorts with outcomes beyond the first year of life are needed.

IMPACT

The current evidence examining associations between SARS-CoV-2 exposure during the neonatal period and developmental outcomes in infancy is limited by there being few studies with extremely small sample sizes. Based on sparse data there was no consistent association between antenatal or neonatal exposure to SARS-CoV-2 infection and an adverse impact on developmental outcomes below 12 months of age for babies born preterm or at term. This study highlights that larger cohorts with outcomes assessed beyond the first year are needed to determine the potential longer-term impact of SARS-CoV-2 infection exposure on child development.

Face-to-face live eye-tracking in toddlers with autism: Feasibility and impact of familiarity and face covering

Studies utilizing eye-tracking methods have potential to promptly capture real-world dynamics of one of the core areas of vulnerability in autism spectrum disorders (ASD), selective social attention. So far, no studies have successfully reported utilizing the method to examine social attention in toddlers with neurodevelopmental vulnerabilities in real world and challenging settings such as an interactive face-to-face. This study examined the feasibility and validity of live eye-tracking method in response to live interaction occurring in several contexts in toddlers with and without ASD. Forty-seven toddlers with ASD, with atypical development (ATYP), or typically developing (TD), underwent a 30-s live eye-tracking procedure during a face-to-face interaction with a masked stranger using child-directed-speech (16 ASD, 14 ATYP, 17 TD; Mage = 23.44 months, SD = 6.02). Out of this group of toddlers, 29 (10 ASD, 8 ATYP, 11 TD, Mage = 21.97 months, SD = 5.76) underwent the same procedure with one of their maskless parent. Task completion rate, calibration accuracy, and affective response (feasibility measures) as well as attention to the task and the social partner (validity measures) were examined. Task completion rate and calibration accuracy were excellent. Despite the challenging context of face-to-face interaction, the toddlers exhibited a neutral affect, and high attention to the task and the speaker. As anticipated, toddlers with ASD looked less at the social partner compared with control groups. However, attention was comparable between the Stranger and Parent conditions, indicating that the effect was consistent regardless of presence of face covering or the familiarity of the interactive partner. The study demonstrates the high feasibility and validity of a live eye-tracking task involving face-to-face interaction in neurodiverse toddlers with social vulnerabilities. The effect of diminished attention to social partners in toddlers with autism is robust and present when interacting with an unfamiliar person and parent. The results suggest that a brief live eye-tracking method constitutes a promising ecologically valid candidate biomarker and potential intervention outcome in autism.

Association of antenatal or neonatal SARS-COV-2 exposure with developmental and respiratory outcomes, and healthcare usage in early childhood: a national prospective cohort study

Background

Perinatal exposure to SARS-CoV-2 may affect neurodevelopment before 12 months of age, but longer-term outcomes remain unknown. We examined whether antenatal or neonatal SARS-CoV-2 exposure compared with non-exposure is associated with neurodevelopment, respiratory symptoms, and health care usage in early childhood.

Methods

This prospective national population-based cohort study was conducted in England and Wales, United Kingdom. We enrolled term-born children (≥37 weeks' gestation) with and without antenatal or neonatal exposure to SARS-CoV-2 infection by approaching parents of eligible children who were cared for in 87 NHS hospitals. Potential participants were identified through the national active surveillance studies of pregnant women and newborn infants hospitalised with confirmed SARS-CoV-2 infection conducted through the UK Obstetric Surveillance System and the British Paediatric Surveillance Unit. We defined antenatal and neonatal SARS-CoV-2 exposure as infants born to mothers hospitalised with confirmed SARS-CoV-2 infection between 14 + 0 and 36 + 6 weeks gestation and infants admitted to hospital with confirmed SARS-CoV-2 infection within the first 28 days after birth. Children born preterm or with major congenital anomaly or who were not residing in the UK were excluded. We assessed children's development (Ages and Stages Questionnaire 3rd Edition (ASQ-3); Ages and Stages Questionnaire Social-Emotional 2nd Edition (ASQ:SE-2)), respiratory symptoms (Liverpool Respiratory Symptom Questionnaire (LRSQ)) and health care usage (parent-completed questionnaire) at 21-32 months of age. Primary outcome: total ASQ-3 score, converted to z-scores. Secondary outcomes: ASQ:SE-2 z-scores; risk of delay in ASQ-3 domains; total LRSQ scores, converted to z-scores. Analyses were adjusted for children's age, sex, maternal ethnicity, parental education, and index of multiple deprivation.

Findings

Between October 20, 2021 and January 27, 2023, we approached 668 and 1877 families out of 712 and 1917 potentially eligible participants in the exposed and comparison cohort. Of the 125 and 306 participants who were enrolled to the exposed and comparison cohort 121 and 301 participants completed the questionnaires and 96 and 243 participants were included in the analysis. In the age adjusted analysis, the mean total ASQ-3 z-score was lower in the exposed than the comparison cohort (-0.3, 95% CI: -0.6 to -0.05), however, when adjusted for sex, parental education, ethnicity and IMD quintile, there was no significant difference (difference in mean z-score = -0.2 95% CI: -0.5 to 0.03). SARS-CoV-2 exposure was associated with increased risk of delayed personal-social skills (odds ratio = 3.81; 95% CI: 1.07-13.66), higher ASQ:SE-2 total z-scores (difference in mean z-score = 0.4; 95% CI: 0.2-0.6) and increased risk of delayed social-emotional development (OR = 3.58, 95% CI: 1.30-9.83), after adjusting for sex, age at assessment, parental education, ethnicity and IMD quintile. The exposed cohort had a higher mean total LRSQ z-score than the comparison cohort (0.3 95% CI: 0-0.6) and higher inpatient (38% vs. 21%, p = 0.0001), outpatient (38% vs. 30%, p = 0.0090), and General Practitioner appointments (60% vs. 50%, p = 0.021) than the comparison cohort, after adjusting for sex, age at assessment, parental education, ethnicity and IMD quintile. No differences in other secondary outcomes between the exposed and comparison cohorts were found.

Interpretation

Although the exposed cohort did not differ from the comparison cohort on the primary outcome, total ASQ-3 score, the exposed cohort were at greater risk of delayed social-emotional development, had a greater prevalence of respiratory symptoms and increased health care usage relative to the comparison cohort. The study is limited by the smaller sample size due to the low response rate and lack of clinical developmental assessments. Given the association of poor social-emotional development with antenatal or neonatal SARS-CoV-2 exposure, developmental screening, and follow-up of children with confirmed antenatal or neonatal SARS-CoV-2 infection may be warranted to identify those in need of early intervention.

Funding

Action Medical Research for Children.

The effect of processing partial information in dynamic face perception

Face perception is a major topic in vision research. Most previous research has concentrated on (holistic) spatial representations of faces, often with static faces as stimuli. However, faces are highly dynamic stimuli containing important temporal information. How sensitive humans are regarding temporal information in dynamic faces is not well understood. Studies investigating temporal information in dynamic faces usually focus on the processing of emotional expressions. However, faces also contain relevant temporal information without any strong emotional expression. To investigate cues that modulate human sensitivity to temporal order, we utilized muted dynamic neutral face videos in two experiments. We varied the orientation of the faces (upright and inverted) and the presence/absence of eye blinks as partial dynamic cues. Participants viewed short, muted, monochromic videos of models vocalizing a widely known text (National Anthem). Videos were played either forward (in the correct temporal order) or backward. Participants were asked to determine the direction of the temporal order for each video, and (at the end of the experiment) whether they had understood the speech. We found that face orientation, and the presence/absence of an eye blink affected sensitivity, criterion (bias) and reaction time: Overall, sensitivity was higher for upright compared to inverted faces, and in the condition where an eye blink was present compared to the condition without an eye blink. Reaction times were mostly faster in the conditions with higher sensitivity. A bias to report inverted faces as 'backward' observed in Experiment I, where upright and inverted faces were presented randomly interleaved within each block, was absent when presenting upright and inverted faces in different blocks in Experiment II. Language comprehension results revealed that there was higher sensitivity when understanding the speech compared to not understanding the speech in both experiments. Taken together, our results showed higher sensitivity with upright compared to inverted faces, suggesting that the perception of dynamic, task-relevant information was superior with the canonical orientation of the faces. Furthermore, partial information coming from eye blinks, in addition to mouth movements, seemed to play a significant role in dynamic face perception, both when faces were presented upright and inverted. We suggest that studying the perception of facial dynamics beyond emotional expressions will help us to better understand the mechanisms underlying the temporal integration of facial information from different -partial and holistic- sources, and that our results show how different strategies, depending on the available information, are employed by human observers when judging the temporal order of faces.

Effects of wearing an opaque or transparent face mask on the perception of facial expressions: A comparative study between Japanese school-aged children and adults

The negative side effects of mask-wearing on reading facial emotional cues have been investigated in several studies with adults post-2020. However, little is known about children. This study aimed to determine the negative influence of mask-wearing on reading emotions of adult faces by Japanese school-aged children, compared to Japanese adults. We also examined whether this negative influence could be alleviated by using a transparent face mask instead of an opaque one (surgical mask). The performance on reading emotions was measured using emotion categorization and emotion intensity rating tasks for adult faces. As per the findings, the accuracy of emotion recognition in children was impaired for various facial expressions (disgust, fear, happy, neutral, sad, and surprise faces), except for angry faces. Conversely, in adults, it was impaired for a few facial expressions. The perceived intensity for happy faces with a surgical mask was weaker in both children and adults than in those without the mask. A negative influence of wearing surgical masks was generally not observed for faces wearing a transparent mask in both children and adults. Thus, negative side effects of mask-wearing on reading emotions are observed for more facial expressions in children than in adults; transparent masks can help remedy these.

Infants' responses to masked and unmasked smiling faces: A longitudinal investigation of social interaction during Covid-19

During the COVID-19 pandemic, face masks became an effective hygienic measure to reduce infection rates. Given the relevance of facial expressions for social interactions, the question arises how face masks affect early social interactions. The current longitudinal study investigated how covering parts of the face might impact infants' responses to others' emotional expressions. Infants who were born during the pandemic were examined at three measurement points at the age of 6, 10 and 14 months. After displaying a neutral facial expression an experimenter smiled at infants while either wearing a mask (mask condition) or not wearing a mask (no mask condition). Infants' change in affect (i.e., negative, neutral, positive) from the neutral to the test phase (i.e., smiling experimenter) was evaluated. Results showed that at 6 and at 10 months infants' behavior did not differ between conditions, whereas at 14 months infants were more likely to show a change from neutral/negative affect to positive affect in the no mask condition than in the mask condition. Moreover, at 14 months infants were less likely to respond positively to the experimenter's smile (across conditions) than at 6 and at 10 months. These findings broaden our understanding of potential effects of mask wearing on the development of face processing and affective communication. Overall, they indicate a developmental trend according to which infants' processing and response to others' positive emotions becomes more selective and differentiated with increasing age.

Developmental and behavioural outcomes at 2 years in babies born during the COVID-19 pandemic: communication concerns in a pandemic birth cohort

INTRODUCTION

The CORAL (Impact of Corona Virus Pandemic on Allergic and Autoimmune Dysregulation in Infants Born During Lockdown) study reported a reduction in social communication milestones in 12-month-old infants born into the COVID-19 pandemic.

AIMS

To look at 24-month developmental and behavioural outcomes in the CORAL cohort.

DESIGN

The CORAL study is a longitudinal prospective observational study of Irish infants born in the first 3 months of the pandemic. At 24 months of age, the Ages and Stages Developmental Questionnaire (ASQ24) and the Child Behaviour Checklist (CBCL) were completed and compared with prepandemic BASELINE (Babies After SCOPE: Evaluating the Longitudinal Impact Using Neurological and Nutritional Impact) cohort.

RESULTS

917 babies (312 CORAL infants and 605 BASELINE infants) were included. At 24 months of age, infants in the CORAL and BASELINE cohorts had similar developmental ASQ24 scores in fine motor, problem solving and personal and social domains but ASQ24 communication scores were significantly lower in the CORAL group compared with the BASELINE cohort (mean (SD) 49.5 (15.1) vs 53.7 (11.6), p<0.01). Infants from the CORAL cohort were more likely to score below standardised cut-offs for developmental concern in the communication domain (11.9% CORAL compared with 5.4% BASELINE, p<0.01). Unadjusted ASQ24 gross motor scores were lower for the pandemic cohort. Fewer CORAL infants fell under 2 SD cut-off in personal-social subdomain. For CBCL, there was no evidence of difference in scores between the cohorts on multivariable analysis.

CONCLUSION

24-month-old pandemic-born infants had largely similar developmental and behavioural scores compared with their prepandemic counterparts. Concerns have been raised in the communication developmental domain.

Real-time monitoring of infant theta power during naturalistic social experiences

Infant-directed speech and direct gaze are important social cues that shape infant's attention to their parents. Traditional methods for probing their effect on infant attention involve a small number of pre-selected screen-based stimuli, which do not capture the complexity of real-world interactions. Here, we used neuroadaptive Bayesian Optimization (NBO) to search a large 'space' of different naturalistic social experiences that systematically varied in their visual (gaze direct to averted) and auditory properties (infant directed speech to nonvocal sounds). We measured oscillatory brain responses (relative theta power) during episodes of naturalistic social experiences in 57 typically developing 6- to 12-month-old infants. Relative theta power was used as input to the NBO algorithm to identify the naturalistic social context that maximally elicited attention in each individual infant. Results showed that individual infants were heterogeneous in the stimulus that elicited maximal theta with no overall stronger attention for direct gaze or infant-directed speech; however, individual differences in attention towards averted gaze were related to interpersonal skills and greater likelihood of preferring speech and direct gaze was observed in infants whose parents showed more positive affect. Our work indicates NBO may be a fruitful method for probing the role of distinct social cues in eliciting attention in naturalistic social contexts at the individual level.

Community diversity and the other-race effect in infancy

The other-race effect (ORE) is characterized by processing advantages for faces of one's own race over faces of another race and is observed at ~9 months of age. Environmental exposure to other races has an impact on the development of the ORE. In the current study, we examined the effects of community racial diversity on the ORE in 9- to 12-month-olds from across the United States. We hypothesized that community racial diversity would influence the amount of experience that infants have with individuals of other races and be an important factor in predicting the ORE across broad regions of the United States. We predicted that infants from more diverse communities would demonstrate successful processing of own- and other-race faces, while infants from less diverse communities would demonstrate successful processing of own-race but not other-race faces. This would indicate that the ORE is exhibited more strongly in infants from less diverse communities than in infants from more diverse communities. Participants completed familiarization and visual paired comparison (VPC) trials with own- and other-race faces in an online study. Our results showed that although the ORE was present, the effect was driven by community members who were the racial majority. Recognition biases were not observed in community racial or ethnic minority participants, potentially due to increased exposure to racial out-group members, which mitigated the development of the ORE in this subset of participants. This study has far-reaching implications in the study of infant face perception, child development, and social justice, as the ORE develops at a young age, and may lead to a complex pattern of racial biases contributing to systemic barriers in society.

Bilingual toddlers show increased attention capture by static faces compared to monolinguals

Bilingual infants rely differently than monolinguals on facial information, such as lip patterns, to differentiate their native languages. This may explain, at least in part, why young monolinguals and bilinguals show differences in social attention. For example, in the first year, bilinguals attend faster and more often to static faces over non-faces than do monolinguals (Mercure et al., 2018). However, the developmental trajectories of these differences are unknown. In this pre-registered study, data were collected from 15- to 18-month-old monolinguals (English) and bilinguals (English and another language) to test whether group differences in face-looking behaviour persist into the second year. We predicted that bilinguals would orient more rapidly and more often to static faces than monolinguals. Results supported the first but not the second hypothesis. This suggests that, even into the second year of life, toddlers' rapid visual orientation to static social stimuli is sensitive to early language experience.

Children's total blindness as a risk factor for early parent-child relationships: preliminary findings from an Italian sample

Background

Vision provides crucial information for parent-child attunement that scaffolds social development from the first months of life. Congenital blindness might affect both parental wellbeing and children's behavior during parent-child interaction. In this study, we compared families of young children with total versus partial blindness to understand the link between residual vision, parenting stress and perceived social support, and children's behavior during parent-child interaction.

Methods

Participants were 42 white parents (21 fathers and 21 mothers) and their congenitally blind children (14 females, mean age = 14.81 months, SD = 10.46) with no co-occurring disability, recruited at the Robert Hollman Foundation rehabilitation centers in Italy. Parents' scores on the Parenting Stress Index and Multidimensional Scale of Perceived Social Support questionnaires, as well as children's behaviors signaling joint engagement during video-recorded episodes of parent-child interaction, were compared between the Total Blindness (TB, n = 12 children with no light perception or light perception in the dark but no quantifiable visual acuity) and Partial Blindness (PB, n = 9 children with a residual visual acuity below 3/60) groups.

Results

We found that parents of TB children had higher parenting stress and lower perceived social support scores than parents of PB children. In fathers, total stress and stress linked to perceiving the child as difficult negatively correlated with perceived support from friends. There was no difference in the time TB and PB children spent displaying joint engagement behaviors during parent-child interaction. However, TB children directed their gaze and face less often toward their parents than PB children. We observed a trend of association between this behavior and maternal stress.

Conclusion

These preliminary results suggest that the complete absence of vision from birth has adverse effects on stress linked to parenting and parental perceived social support. These findings support the importance of early family-centered interventions that extend to the parents' communities and facilitate the parent-child dyad's communication through non-visual behaviors. Replication is warranted in larger and more diverse samples.

The effect of masks on the visual preference for faces in the first year of life

To prevent the spread of COVID-19, face masks were mandatory in many public spaces around the world. Since faces are the gateway to early social cognition, this raised major concerns about the effect face masks may have on infants' attention to faces as well as on their language and social development. The goal of the present study was to assess how face masks modulate infants' attention to faces over the course of the first year of life. We measured 3, 6, 9, and 12-month-olds' looking behavior using a paired visual preference paradigm under two experimental conditions. First, we tested infants' preference for upright masked or unmasked faces of the same female individual. We found that regardless of age, infants looked equally long at the masked and unmasked faces. Second, we compared infants' attention to an upright masked versus an inverted masked face. Three- and 6-month-olds looked equally long to the masked faces when they were upright or inverted. However, 9- and 12-month-old infants showed a novelty preference for the inverted masked face. Our findings suggest that more experience with faces, including masked faces, leads to efficient adaptations of infants' visual system for processing impoverished social stimuli, such as partially occluded faces.

Face processing in the infant brain after pandemic lockdown

The role of visual experience in the development of face processing has long been debated. We present a new angle on this question through a serendipitous study that cannot easily be repeated. Infants viewed short blocks of faces during fMRI in a repetition suppression task. The same identity was presented multiple times in half of the blocks (repeat condition) and different identities were presented once each in the other half (novel condition). In adults, the fusiform face area (FFA) tends to show greater neural activity for novel versus repeat blocks in such designs, suggesting that it can distinguish same versus different face identities. As part of an ongoing study, we collected data before the COVID-19 pandemic and after an initial local lockdown was lifted. The resulting sample of 12 infants (9-24 months) divided equally into pre- and post-lockdown groups with matching ages and data quantity/quality. The groups had strikingly different FFA responses: pre-lockdown infants showed repetition suppression (novel > repeat), whereas post-lockdown infants showed the opposite (repeat > novel), often referred to as repetition enhancement. These findings provide speculative evidence that altered visual experience during the lockdown, or other correlated environmental changes, may have affected face processing in the infant brain.

How experience shapes infants' communicative behaviour: Comparing gaze following in infants with and without pandemic experience

The COVID-19 pandemic has been influencing people's social life substantially. Everybody, including infants and children needed to adapt to changes in social interactions (e.g., social distancing) and to seeing other people wearing facial masks. In this study, we investigated whether these pandemic-related changes influenced 12- to 15-months-old infants' reactions to observed gaze shifts (i.e., their gaze following). In two eye-tracking tasks, we measured infants' gaze-following behavior during the pandemic (with-COVID-19-experience sample) and compared it to data of infants tested before the pandemic (no-COVID-19-experience sample). Overall, the results indicated no significant differences between the two samples. However, in one sub-task infants in the with-COVID-19-experience sample looked longer at the eyes of a model compared to the no-COVID-19-experience sample. Within the with-COVID-19-experience sample, the amount of mask exposure and the number of contacts without mask were not related to infants' gaze-following behavior. We speculate that even though infants encounter fewer different people during the pandemic and are increasingly exposed to people wearing facial masks, they still also see non-covered faces. These contacts might be sufficient to provide infants with the social input they need to develop social and emotional competencies such as gaze following.