Individual differences in pupil dilation to others' emotional and neutral eyes with varying pupil sizes.

Sensitivity to others' emotional signals is an important factor for social interaction. While many studies of emotional reactivity focus on facial emotional expressions, signals such as pupil dilation which can indicate arousal, may also affect observers. For example, observers' pupils dilate when viewing someone with dilated pupils, so-called pupillary contagion. Yet it is unclear how pupil size and emotional expression interact as signals. Further, examining individual differences in emotional reactivity to others can shed light on its mechanisms and potential outcomes. In the current study, adults' (N = 453) pupil size was assessed while they viewed images of the eye region of individuals varying in emotional expression (neutral, happy, sad, fearful, angry) and pupil size (large, medium, small). Participants showed pupillary contagion regardless of the emotional expression. Individual differences in demographics (gender, age, socioeconomic status) and psychosocial factors (anxiety, depression, sleep problems) were also examined, yet the only factor related to pupillary contagion was socioeconomic status, with higher socioeconomic status predicting less pupillary contagion for emotionally-neutral stimuli. The results suggest that while pupillary contagion is a robust phenomenon, it can vary meaningfully across individuals.

Twelve-month-old infants' physiological responses to music are affected by others' positive and negative reactions.

Infants show remarkable skills for processing music in the first year of life. Such skills are believed to foster social and communicative development, yet little is known about how infants' own preferences for music develop and whether social information plays a role. Here, we investigate whether the reactions of another person influence infants' responses to music. Specifically, 12-month-olds (N = 33) saw an actor react positively or negatively after listening to clips of instrumental music. Arousal (measured via pupil dilation) and attention (measured via looking time) were assessed when infants later heard the clips without the actor visible. Results showed greater pupil dilation when listening to music clips that had previously been reacted to negatively than those that had been reacted to positively (Exp. 1). This effect was not replicated when a similar, rather than identical, clip from the piece of music was used in the test phase (Exp. 2, N = 35 12-month-olds). There were no effects of the actor's positive or negative reaction on looking time. Together, our findings suggest that infants are sensitive to others' positive and negative reactions not only for concrete objects, such as food or toys, but also for more abstract stimuli including music.

Gaze Following Is Not Dependent on Ostensive Cues: A Critical Test of Natural Pedagogy.

The theory of natural pedagogy stipulates that infants follow gaze because they are sensitive to the communicative intent of others. According to this theory, gaze following should be present if, and only if, accompanied by at least one of a set of specific ostensive cues. The current article demonstrates gaze following in a range of contexts, both with and without expressions of communicative intent in a between-subjects design with a large sample of 6-month-old infants (n = 94). Thus, conceptually replicating prior results from Szufnarowska et al. (2014) and falsifying a central pillar of the natural pedagogy theory. The results suggest that there are opportunities to learn from others' gaze independently of their displayed communicative intent.

Infants' use of movement synchrony to infer social affiliation in others.

Infants socially engage with others and observe others' social interactions from early in life. One characteristic found to be important for signaling and establishing affiliative social relationships is physical coordination and synchronization of movements. This study investigated whether synchrony in others' movements signals affiliation to 12- and 15-month-old infants. The infants were shown a scene in which two characters moved either synchronously or non-synchronously with a third character in the center. Next, the center character made an affiliation declaration and subsequently approached and cuddled one of the two characters. Using measures of gaze, we gauged infants' inferences about whom the center character would affiliate with before the cuddling took place. We found that 15-month-olds, but not 12-month-olds, inferred that the center character would affiliate with the previously synchronous character, suggesting that they can make inferences about others' affiliation based on movement synchrony. The findings are discussed in terms of their relevance to the infants' personal preferences and the potential importance of first-person experience in the development of social cognition.

Early preschool environments and gender: Effects of gender pedagogy in Sweden.

To test how early social environments affect children's consideration of gender, 3- to 6-year-old children (N=80) enrolled in gender-neutral or typical preschool programs in the central district of a large Swedish city completed measures designed to assess their gender-based social preferences, stereotypes, and automatic encoding. Compared with children in typical preschools, a greater proportion of children in the gender-neutral school were interested in playing with unfamiliar other-gender children. In addition, children attending the gender-neutral preschool scored lower on a gender stereotyping measure than children attending typical preschools. Children at the gender-neutral school, however, were not less likely to automatically encode others' gender. The findings suggest that gender-neutral pedagogy has moderate effects on how children think and feel about people of different genders but might not affect children's tendency to spontaneously notice gender.

Pupillary Contagion in Infancy: Evidence for Spontaneous Transfer of Arousal.

Pupillary contagion-responding to pupil size observed in other people with changes in one's own pupil-has been found in adults and suggests that arousal and other internal states could be transferred across individuals using a subtle physiological cue. Examining this phenomenon developmentally gives insight into its origins and underlying mechanisms, such as whether it is an automatic adaptation already present in infancy. In the current study, 6- and 9-month-olds viewed schematic depictions of eyes with smaller and larger pupils-pairs of concentric circles with smaller and larger black centers-while their own pupil sizes were recorded. Control stimuli were comparable squares. For both age groups, infants' pupil size was greater when they viewed large-center circles than when they viewed small-center circles, and no differences were found for large-center compared with small-center squares. The findings suggest that infants are sensitive and responsive to subtle cues to other people's internal states, a mechanism that would be beneficial for early social development.

Callous-unemotional traits affect adolescents' perception of collaboration.

BACKGROUND: How is the perception of collaboration influenced by individual characteristics, in particular high levels of callous-unemotional (CU) traits? CU traits are associated with low empathy and endorsement of negative social goals such as dominance and forced respect. Thus, it is possible that they could relate to difficulties in interpreting that others are collaborating based on a shared goal. METHODS: In the current study, a community sample of 15- to 16-year olds participated in an eye tracking task measuring whether they expect that others engaged in an action sequence are collaborating, depending on the emotion they display toward each other. Positive emotion would indicate that they share a goal, while negative emotion would indicate that they hold individual goals. RESULTS: When the actors showed positive emotion toward each other, expectations of collaboration varied with CU traits. The higher adolescents were on CU traits, the less likely they were to expect collaboration. When the actors showed negative emotion toward each other, CU traits did not influence expectations of collaboration. CONCLUSIONS: The findings suggest that CU traits are associated with difficulty in perceiving positive social interactions, which could further contribute to the behavioral and emotional problems common to those with high CU traits.

Rock with me: the role of movement synchrony in infants' social and nonsocial choices.

Matching the timing of one's movements to the movements of others has been proposed to increase affiliation and prosociality. Although coordinated movements facilitate early social interactions, not much is known about the mechanisms and effects of movement synchrony throughout development. Two studies investigated 12-month-olds' (Study 1, N = 40) and 9-month-olds' (Study 2, N = 41) preferences for synchronous others in a social as opposed to a nonsocial context. It was found that movement synchrony exclusively guides infants' social choices at 12 months. In contrast, 9-month-olds did not show any preferences for synchronous movements in social or nonsocial contexts. Results suggest that movement synchrony is important in guiding infants' social preferences and its effects emerge toward the end of the 1st year of life.

Six weeks of unsupervised Nintendo Wii Fit gaming is effective at improving balance in independent older adults.

OBJECTIVE: To determine the effectiveness of unsupervised Nintendo Wii Fit balance training in older adults. METHODS: Forty-one older adults were recruited from local retirement villages and educational settings to participate in a six-week two-group repeated measures study. The Wii group (n = 19, 75 ± 6 years) undertook 30 min of unsupervised Wii balance gaming three times per week in their retirement village while the comparison group (n = 22, 74 ± 5 years) continued with their usual exercise program. Participants' balance abilities were assessed pre- and postintervention. RESULTS: The Wii Fit group demonstrated significant improvements (P < .05) in timed up-and-go, left single-leg balance, lateral reach (left and right), and gait speed compared with the comparison group. Reported levels of enjoyment following game play increased during the study. CONCLUSION: Six weeks of unsupervised Wii balance training is an effective modality for improving balance in independent older adults.

Infants use social context to bind actions into a collaborative sequence.

Eye tracking was used to show that 18-month-old infants are sensitive to social context as a sign that others' actions are bound together as a collaborative sequence based on a joint goal. Infants observed five identical demonstrations in which Actor 1 moved a block to one location and Actor 2 moved the same block to a new location, creating a sequence of actions that could be considered either individual actions or collaboration. In the test phase, Actor 1 was alone and sitting so that she could reach both locations. The question was whether she would place a new block in the location she had previously (individual goal) or in the location that could be considered the goal of collaboration (joint goal). Importantly, in the Social condition, the actors were socially engaged with each other before and during the demonstration, while in the Non-Social condition, they were not. Results revealed that infants in the Social condition spontaneously anticipated Actor 1 placing her block in the joint goal location more often than those in the Non-Social condition. Thus, the social context seems to allow infants to bind actions into a collaborative sequence and anticipate joint rather than individual goals, giving insight into how actions are perceived using top-down processing early in life.

The Synchrony-Prosociality Link Cannot Be Explained Away as Expectancy Effect: Response to Atwood et al. ().

Moving in time to others, as is often observed in dance, music, sports and much of children's play cross-culturally, is thought to make people feel and act more prosocially towards each other. In a recent paper, Atwood et al. (2022) argued that the inferential validity of this link found between synchronous behaviour and prosociality might be mainly due to "expectancy effects generated by a combination of (1) experimenter expectancy, leading to experimenter bias; and (2) participant expectancy (i.e., placebo effects)". Here, we counter these arguments with (1) examples of studies devoid of experimenter expectancy effects that nevertheless demonstrate a positive link between synchrony and prosociality, and (2) insights from the developmental literature that address participant expectancy by showing how expectations formed through lived experiences of synchronous interactions do not necessarily threaten inferential validity. In conclusion, there is already sufficient good-quality evidence showing the positive effects of synchronous behaviours on prosociality beyond what can be explained by experimenter or participant expectation effects.

Williams syndrome: reduced orienting to other's eyes in a hypersocial phenotype.

Williams syndrome (WS) is a rare genetic condition associated with high sociability, intellectual disability, and social cognitive challenges. Attention to others' eyes is crucial for social understanding. Orienting to, and from other's eyes was studied in WS (n = 37, mean age = 23, age range 9-53). The WS group was compared to a typically developing comparison participants (n = 167) in stratified age groups from infancy to adulthood. Typically developing children and adults were quicker and more likely to orient to eyes than the mouth. This bias was absent in WS. The WS group had reduced peak saccadic velocities, indicating hypo-arousal. The current study indicates reduced orienting to others' eyes in WS, which may affect social interaction skills.

No transfer of arousal from other's eyes in Williams syndrome.

Typically developing humans automatically synchronize their arousal levels, resulting in pupillary contagion, or spontaneous adaptation of pupil size to that of others. This phenomenon emerges in infancy and is believed to facilitate social interaction. Williams syndrome (WS) is a genetic condition characterized by a hyper-social personality and social interaction challenges. Pupillary contagion was examined in individuals with WS (n = 44), age-parallel-matched typically developing children and adults (n = 65), and infants (n = 79). Bayesian statistics were used. As a group, people with WS did not show pupillary contagion (Bayes factors supporting the null: 25-50) whereas control groups did. This suggests a very early emerging atypical developmental trajectory. In WS, higher pupillary contagion was associated with lower autistic symptoms of social communication. Diminished synchronization of arousal may explain why individuals with WS have social challenges, whereas synchronization of arousal is not a necessary correlate of high social motivation.

Observation and initiation of joint action in infants.

Infants imitate others' individual actions, but do they also replicate others' joint activities? To examine whether observing joint action influences infants' initiation of joint action, forty-eight 18-month-old infants observed object demonstrations by 2 models acting together (joint action), 2 models acting individually (individual action), or 1 model acting alone (solitary action). Infants' behavior was examined after they were given each object. Infants in the joint action condition attempted to initiate joint action more often than infants in the other conditions, yet they were equally likely to communicate for other reasons and to imitate the demonstrated object-directed actions. The findings suggest that infants learn to replicate others' joint activity through observation, an important skill for cultural transmission of shared practices.

Kids attend to saliva sharing to infer social relationships.

Saliva sharing suggests "thick," intimate bonds.

Humans' pupillary contagion extends to cats and dogs.

When viewing pupil sizes change, our own pupil sizes change, a phenomenon known as pupillary contagion. This involuntary response is reliable between humans but can be affected by familiarity and empathy. We investigated whether the pupillary contagion response occurs for humans viewing familiar species-cats and dogs-and whether it is modulated by preferences for particular species. Pupil sizes were measured while viewing cat, dog and human images with small, medium and large pupils. Trait empathy, cat and dog affiliation and experience were subsequently measured. There was an image pupil size effect, but this did not vary by species. There was greater pupil size change to cats and dogs than to humans, but this might have been due to the varying size and appearance of the cats and dogs. Greater dog affiliation was also associated with smaller overall pupil size change to dogs and larger change to humans, but this did not interact with image pupil size. Dog affiliation might be associated with less arousal to dog images. In sum, pupillary contagion responses indicate a spontaneous transfer of information about internal states and the findings suggest that humans are sensitive to this across species, regardless of individual preference.

Similarity predicts liking in 3-year-old children.

Two studies examined the influence of similarity on 3-year-old children's initial liking of their peers. Children were presented with pairs of childlike puppets who were either similar or dissimilar to them on a specified dimension and then were asked to choose one of the puppets to play with as a measure of liking. Children selected the puppet whose food preferences or physical appearance matched their own. Unpacking the physical appearance finding revealed that the stable similarity of hair color may influence liking more strongly than the transient similarity of shirt color. A second study showed that children also prefer to play with a peer who shares their toy preferences, yet importantly, show no bias toward a peer who is similar on an arbitrary dimension. The findings provide insight into the earliest development of peer relations in young children.

The Role of Callous-Unemotional Traits on Adolescent Positive and Negative Emotional Reactivity: A Longitudinal Community-Based Study.

Callous-unemotional (CU) traits are associated with lower emotional reactivity in adolescents. However, since previous studies have focused mainly on reactivity to negative stimuli, it is unclear whether reactivity to positive stimuli is also affected. Further, few studies have addressed the link between CU traits and emotional reactivity in longitudinal community samples, which is important for determining its generalizability and developmental course. In the current study, pupil dilation and self-ratings of arousal and valence were assessed in 100 adolescents (15-17 years) from a community sample, while viewing images with negative and positive valence from the International Affective Pictures System (IAPS). Behavioral traits (CU) were assessed concurrently, as well as at ages 12-15, and 8-9 (subsample, n = 68, low levels of prosocial behavior were used as a proxy for CU traits). The results demonstrate that CU traits assessed at ages 12-15 and 8-9 predicted less pupil dilation to both positive and negative images at ages 15-17. Further, CU traits at ages 12-15 and concurrently were associated with less negative valence ratings for negative images and concurrently to less positive valence ratings for positive images. The current findings demonstrate that CU traits are related to lower emotional reactivity to both negative and positive stimuli in adolescents from a community sample.

Preschoolers' conformity (and its motivation) is linked to own and parents' personalities.

Previous studies on conformity have primarily focused on factors that moderate conformity rates overall and paid little attention to explaining the individual differences. In this study, we investigate five-factor model personality traits of both parents and children and experimentally elicited conformity in 3.5-year-olds (N = 59) using an Asch-like paradigm with which we measure both overt conformity (public responses) and covert opinions (private beliefs after conformist responses): A correct covert opinion after an incorrect conformist response results from a socially normative motivation, whereas an incorrect covert opinion results from an informational motivation. Our data show (1) low parental extroversion is associated with participants' overall rate of conformity, (2) and low participant extroversion and high openness are associated with an informational instead of a normative motivation to conform. This suggests that sensitivity to the social context or social engagement level, as manifested through extroversion, could be an important factor in conformist behaviour. Statement of contribution What is already known on this subject? We all conform, from early in life - and even when we should know better We can conform for normative and informational motivations Some are more prone to conform than others What does this study add? This is the first study to take an individual differences approach to developmental conformity Social engagement (extroversion) is an important factor in conformity.

Author Correction: Human eyes with dilated pupils induce pupillary contagion in infants.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.