Group membership and social status modulate joint actions

Interpersonal prior information informs ensemble coding through the co-representation process

Humans have the ability to rapidly extract summary statistics from object groupings through a specific capability known as ensemble coding. Previous literature has reported that this ability can become biased by prior perceptual experiences at the individual level. However, it remains unknown whether interpersonal prior information could also bias ensemble perception through a co-representation process. Experiment 1 found that participants' summary estimations were biased toward their co-actor's stimuli. Experiment 2 confirmed a causal relationship between the bias effect and the co-representation process by showing a reduction in biased estimation after pairing participants with an out-group partner. These findings extend the sources of prior information exploited by humans during perceptual average from individual-level information (i.e., self-tasks) to interpersonal-level information (i.e., co-actor's tasks). More specifically, interpersonal prior information is shown to act in a top-down and implicit manner, biasing ensemble perception.

Linguistic identity as a modulator of gaze cueing of attention

Eye-gaze stimuli can elicit orienting of attention in an observer, a phenomenon known as gaze cueing of attention. Here, we explored whether gaze cueing can be shaped by the linguistic identity of the cueing face. In two experiments, participants were first familiarized with different faces together with auditory sentences. Half of the sentences were associated with the native language of the participants (Italian) and the other half with an unknown language (Albanian and Basque, in Experiments 1 and 2, respectively). In a second phase, participants performed a gaze-cueing task. In a third recognition phase, the auditory sentences were presented again, and participants were required to decide which face uttered each sentence. Results indicated that participants were more likely to confuse faces from the same language category than from the other language category. Results of the gaze-cueing task revealed a greater gaze-cueing effect for faces associated with the native vs. unknown language. Critically, this difference emerged only in Experiment 1, which may reflect differences in social status between the two language groups. Our findings revealed the impact of language as a social cue on the gaze-cueing effect, suggesting that social attention is sensitive to the language of our interlocutors.

Action prediction modulates self-other integration in joint action

People often coordinate actions with others, requiring an adjustable amount of self-other integration between actor's and co-actor's actions. Previous research suggests that such self-other integration (indexed by the joint Simon effect) is enhanced by agent similarity of the co-actor (e.g., high in intentionality). In this study, we aimed to extend this line of research by testing whether experiencing agency over a co-actor's actions (vicarious agency) and/or action prediction strengthens the joint Simon effect. For this purpose, we manipulated experienced agency by varying the experienced control over a co-actor's actions (Experiment 1), and action prediction regarding the co-actor's actions (Experiment 2). Vicarious agency could effectively be induced, but did not modulate the size of the joint Simon effect. The joint Simon effect was decreased when the co-actor's actions were unpredictable (vs. predictable) during joint task performance. These findings suggest social agency can be induced and effectively measured in joint action. Action prediction can act as an effective agency cue modulating the amount of self-other integration in joint action.

The presence of adjacent others facilitates interpersonal neural synchronization in the left prefrontal cortex during a simple addition task

The hyperscanning technique, that is, simultaneous measurement of neural signals in more than one person, is a powerful research tool for understanding humans' social interactions. In recent years, many studies have investigated interpersonal neural synchronization during various types of communication processes. However, there has been little focus on the impact of the presence of others without explicit social interaction, despite the mere presence of others having been suggested as influencing behavior. In this study, we clarify whether neural signals during a self-paced, repeated, addition task are synchronized when another individual is adjacent without direct interaction. Twenty pairs of participants were measured using a hyperscanning approach with near-infrared spectroscopy. The results show that interpersonal neural synchronization of the task-related signal in the left forehead region was enhanced under the condition of being adjacent to another participant. By contrast, a significant decrease in neural synchronization in the center of the forehead region, where increased neural synchronization is often reported in explicit communication, was observed. Thus, the results indicate that the adjacency of others modulates interpersonal neural synchronization in the task-related signal, and the effect on cognitive processing is different from that of explicit social interaction.

End in view: Joint end-state comfort depends on gaze and extraversion

This study investigated how humans adapt to a partner's movement in a joint pick-and-place task and examined the role of gaze behavior and personality traits in adapting to a partner. Two participants sitting side-by-side transported a cup from one end of a table to the other. The participant sitting on the left (the agent) moved the cup to an intermediate position from where the participant sitting on the right (the partner) transported it to a goal position with varying orientations. Hand, finger, cup movements and gaze behavior were recorded synchronously via motion tracking and portable eye tracking devices. Results showed interindividual differences in the extent of the agents' motor adaptation to the joint action goal, which were accompanied by differences in gaze patterns. The longer agents directed their gaze to a cue indicating the goal orientation, the more they adapted the rotation of the cup's handle when placing it at the intermediate position. Personality trait assessment showed that higher extraverted tendencies to strive for social potency went along with more adaptation to the joint goal. These results indicate that agents who consider their partner's end-state comfort use their gaze to gather more information about the joint action goal compared to agents who do not. Moreover, the disposition to enjoy leadership and make decisions in interpersonal situations seems to play a role in determining who adapts to a partner's task in joint action.

Action co-representation under threat: A Social Simon study

Several studies have shown that individuals automatically integrate the actions of other individuals into their own action plans, thus facilitating action coordination. What happens to this mechanism in situations of danger? This capacity could either be reduced, in order to allocate more cognitive resources for individualistic actions, or be maintained or enhanced to enable cooperation under threat. In order to determine the impact of the perception of danger on this capacity, two groups of participants carried out, in pairs, the Social Simon task, which provides a measure of co-representation. The task was performed during so-called 'threat blocks' (during which participants could be exposed at any time to an aversive stimulus) and so-called 'safety blocks' (during which no aversive stimulation could occur). In a first group of participants, both individuals were exposed at the same time to threat blocks. In a second group, only one of the two participants was exposed to them at a time. Our results indicate that co-representation, an important cognitive mechanism for cooperation, (i) is preserved in situations of danger; and (ii) may even be increased in participants who are confronted alone to threat but in the presence of a safe partner. Contrarily to popular belief, danger does not shut down our capacities for social interaction.

The influence of social context and social connection on visual perceptual processes

The aim of this study was twofold: (1) to re-test whether a minimal social context has an influence on gaze patterns, and (2) to determine if a social connection (i.e., friendship) has a modulatory effect on gaze patterns in a minimal social context. In Experiment 1, two unacquainted participants were paired and seated at separate testing stations in the same room. At the beginning of each trial, participants were informed whether they were looking at different image sets (solo trials), or the same image set (joint trials). Image sets consisted of a positive, a negative, and two neutral images. No explicit task instructions were provided and there was no interaction between participants during the task. Experiment 2 was identical to Experiment 1, except that participants were paired with a friend. The fixation-based metrics of interest were time to first fixation (TFF) and total fixation duration (TFD). The findings revealed that social context has a modulatory effect on attentional capture (i.e., TFF) irrespective of social connection. Unexpectedly, a negativity bias was found to hold attention (i.e., TFD) regardless of social context. However, having a social connection did increase the time spent looking at positive images on the joint trials. Having a social connection with another person seems to alter looking behaviour such that more time is spent looking at positive images on the joint trials compared to the solo trials. These findings highlight the importance of evaluating both TFD and TFF to develop a better understanding of the factors underlying joint perception.

Competence-based social status and implicit preference modulate the ability to coordinate during a joint grasping task

Studies indicate that social status influences people's social perceptions. Less information is available about whether induced social status influences dyadic coordination during motor interactions. To explore this issue, we designed a study in which two confederates obtained high or low competence-based status by playing a game together with the participant, while the participant always occupied the middle position of the hierarchy. Following this status-inducing phase, participants were engaged in a joint grasping task with the high- and low-status confederates in different sessions while behavioural (i.e., interpersonal asynchrony and movement start time) indexes were measured. Participants' performance in the task (i.e., level of interpersonal asynchrony) when interacting with the low-status partner was modulated by their preference for him. The lower participants' preference for a low- relative to a high-status confederate, the worse participants' performance when interacting with the low-status confederate. Our results show that participants' performance during motor interactions changes according to the social status of the interaction partner.

Anticipation in sociomotor actions: Similar effects for in- and outgroup interactions

In social interactions, own actions often trigger a particular response from another person. The sociomotor framework proposes that this consistent behavior of others can become incorporated into own action control. In line with this idea, recent studies have shown that own motor actions are facilitated if they are predictably being imitated rather than counterimitated by a social interaction partner. In the present study, we investigated whether this finding is influenced by the relationship between the interacting persons. To that end, we manipulated whether a participant was being imitated and counterimitated by an ingroup or by an outgroup member. In two experiments, we found a beneficial influence of being imitated irrespective of group membership. The results suggest that, while people incorporated their partner's behavior into own action control, this was not further qualified by group membership as a higher-order social variable. This finding points to a universal account of action control for actions with social action effects and actions with inanimate action effects alike.

No evidence for shared representations of task sets in joint task switching

It has been suggested that actors co-represent a shared task context when they perform a task in a joint fashion. The present study examined the possibility of co-representation in joint task switching, in which two actors shared two tasks that switched randomly across trials. Experiment 1 showed that when an actor performed the tasks individually, switch costs were obtained if the actors responded on the previous trial (go trial), but not if they did not respond (no-go trial). When two actors performed the tasks jointly, switch costs were obtained if the actor responded on the previous trial (actor-repeat trials) but not if the co-actor responded (actor-switch trials). In Experiment 2, a single actor performed both tasks of the joint condition to test whether the findings of Experiment 1 were due to the use of different response sets by the two actors. Switch costs were obtained for both repetitions and alternations of the response set, which rules out this possibility. Taken together, our findings provided little support for the idea that actors co-represent the task sets of their co-actors.

Action-effect sharing induces task-set sharing in joint task switching

A central issue in the study of joint task performance has been one of whether co-acting individuals perform their partner's part of the task as if it were their own. The present study addressed this issue by using joint task switching. A pair of actors shared two tasks that were presented in a random order, whereby the relevant task and actor were cued on each trial. Responses produced action effects that were either shared or separate between co-actors. When co-actors produced separate action effects, switch costs were obtained within the same actor (i.e., when the same actor performed consecutive trials) but not between co-actors (when different actors performed consecutive trials), implying that actors did not perform their co-actor's part. When the same action effects were shared between co-actors, however, switch costs were also obtained between co-actors, implying that actors did perform their co-actor's part. The results indicated that shared action effects induce task-set sharing between co-acting individuals.

Examining ecological validity in social interaction: problems of visual fidelity, gaze, and social potential

Social interaction is an essential part of the human experience, and much work has been done to study it. However, several common approaches to examining social interactions in psychological research may inadvertently either unnaturally constrain the observed behaviour by causing it to deviate from naturalistic performance, or introduce unwanted sources of variance. In particular, these sources are the differences between naturalistic and experimental behaviour that occur from changes in visual fidelity (quality of the observed stimuli), gaze (whether it is controlled for in the stimuli), and social potential (potential for the stimuli to provide actual interaction). We expand on these possible sources of extraneous variance and why they may be important. We review the ways in which experimenters have developed novel designs to remove these sources of extraneous variance. New experimental designs using a 'two-person' approach are argued to be one of the most effective ways to develop more ecologically valid measures of social interaction, and we suggest that future work on social interaction should use these designs wherever possible.