The joint Simon effect: a review and theoretical integration

Does implicit mentalizing involve the representation of others' mental state content? Examining domain-specificity with an adapted Joint Simon task

Implicit mentalizing involves the automatic awareness of others' perspectives, but its domain-specificity is debated. The Joint Simon task demonstrates implicit mentalizing as a Joint Simon effect (JSE), proposed to stem from spontaneous action co-representation of a social partner's frame of reference in the Joint (but not Individual) task. However, evidence also shows that any sufficiently salient entity (not necessarily social) can induce the JSE. Here, we investigated the content of co-representation through a novel Joint Simon task where participants viewed a set of distinct images assigned to either themselves or their partner. Critically, a surprise image recognition task allowed us to identify partner-driven effects exclusive to the Joint task-sharing condition, versus the Individual condition. We did not observe a significant JSE, preventing us from drawing confident conclusions about the effect's domain-specificity. However, the recognition task results revealed that participants in the Joint task did not recognize their partner's stimuli more accurately than participants in the Individual task. This implies that participants were no more likely to encode content from their partner's perspective during the Joint task. Overall, this study pushes methodological boundaries regarding the elicitation of co-representation in the Joint Simon task and demonstrates the potential utility of a surprise recognition task.

Mirror game as a tool to influence interpersonal spontaneous behavior after performance

Mirror game (MG) is an exercise in which participants imitate each other. Our study explored its spontaneous behavioral consequences after performance. In a baseline (BL) phase, two participants performed a joint Simon task. Then, they performed a lure task during which we measured the interpersonal distance they spontaneously adopted. The BL phase was followed by two phases (in counterbalanced order). The MG phase started with a MG, before a procedure like the BL phase. The individual movement (IM) phase started with movements performed alone before a procedure like the BL phase. Interpersonal distance analysis suggested that MG enhanced spontaneous approach toward the partner, whereas IM induced spontaneous avoidance. Moreover, the joint Simon effect (JSE) tended to be smaller after IM, suggesting a decreasing inclination to integrate the partner's response in one's own action plan. Furthermore, in IM phase, JSE decreased as interpersonal distance increased.

The neutral condition in conflict tasks: On the violation of the midpoint assumption in reaction time trends

Although the relation between congruent and incongruent conditions in conflict tasks has been the primary focus of cognitive control studies, the neutral condition is often set as a baseline directly between the two conditions. However, empirical evidence suggests that the average neutral reaction time (RT) is not placed evenly between the two opposing conditions. This article set out to establish two things: First, to reinforce the informative nature of the neutral condition and second, to highlight how it can be useful for modelling. We explored how RT in the neutral condition of conflict tasks (Stroop, Flanker, and Simon Tasks) deviated from the predictions of current diffusion models. Current diffusion models of conflict tasks predict a neutral RT that is the average of the congruent and incongruent RT, called the midpoint assumption. To investigate this, we first conducted a cursory limited search that recorded the average RT's of conflict tasks with neutral conditions. Upon finding evidence of a midpoint assumption violation which showed a larger disparity between average neutral and incongruent RT, we tested the previously mentioned conflict tasks with two different sets of stimuli to establish the robustness of the effect. The midpoint assumption violation is sometimes inconsistent with the prediction of diffusion models of conflict processing (e.g., the Diffusion Model of Conflict), suggesting possible elaborations of such models.

The Joint Simon task is not joint for capuchin monkeys

Human cooperation can be facilitated by the ability to create a mental representation of one's own actions, as well as the actions of a partner, known as action co-representation. Even though other species also cooperate extensively, it is still unclear whether they have similar capacities. The Joint Simon task is a two-player task developed to investigate this action co-representation. We tested brown capuchin monkeys (Sapajus [Cebus] apella), a highly cooperative species, on a computerized Joint Simon task and found that, in line with previous research, the capuchins' performance was compatible with co-representation. However, a deeper exploration of the monkeys' responses showed that they, and potentially monkeys in previous studies, did not understand the control conditions, which precludes the interpretation of the results as a social phenomenon. Indeed, further testing to investigate alternative explanations demonstrated that our results were due to low-level cues, rather than action co-representation. This suggests that the Joint Simon task, at least in its current form, cannot determine whether non-human species co-represent their partner's role in joint tasks.

Examination of the joint Simon effect in rats: Changes in task performance based on actions of the partner

Nonhuman animals have demonstrated various cooperative behaviors; however, many examples can be interpreted as individual contributions to a task rather than true behavioral coordination. In this study, we used the joint Simon task in rats to determine whether the presence of and task sharing with a partner affected performance in a joint activity. Rats were trained to discriminate between two auditory stimuli (3 and 12 kHz tones) and individually performed an auditory Simon task. They were paired with another rat and tested to perform half of the task, while the other rat performed the other half (joint task condition). The Simon effect was confirmed when the two rats completed half of a joint task. In contrast, when they were placed side by side but only one rat completed half of the task, the Simon effect was not observed. Further analyses revealed that the Simon effect observed in the joint task could not be explained by the simple addition of the two half tasks. In conclusion, task sharing affected individual performance in rats.

Conflict detection and resolution in macaque frontal eye fields

Stimulus-induced conflicts in decision-making tasks produce both behavioral and neuronal congruency effects. However, how and when conflicts are detected and resolved at the neuronal level remains largely unclear. To address these issues, we recorded from single neurons in the frontal eye fields of two macaques performing a conflict task. Although the temporal dynamics of the neuronal congruency effects are independent of the specific task rules, they are substantially different in target- and distractor-encoding neurons. Conflicts were detected ~100 ms after the conflict-inducing cue (20-30 ms after the visual response), which is much faster than predicted based on human EEG results. This suggests that conflict detection relies on a fast mechanism in frontal eye fields. Resolving the conflict at the neuronal level, however, requires between <400 ms to ~1000 ms, and shows profound interindividual differences and depends on task rules, indicating that it is a more complex and top-down driven process. Our findings illuminate the neuronal mechanisms underlying decision-making when a conflict is present, a crucial cognitive process playing a role in basic survival and high-level cognitive functions.

Influence of interpersonal distance on collaborative performance in the joint Simon task-An fNIRS-based hyperscanning study

Collaboration is a critical skill in everyday life. It has been suggested that collaborative performance may be influenced by social factors such as interpersonal distance, which is defined as the perceived psychological distance between individuals. Previous literature has reported that close interpersonal distance may promote the level of self-other integration between interacting members, and in turn, enhance collaborative performance. These studies mainly focused on interdependent collaboration, which requires high levels of shared representations and self-other integration. However, little is known about the effect of interpersonal distance on independent collaboration (e.g., the joint Simon task), in which individuals perform the task independently while the final outcome is determined by the parties. To address this issue, we simultaneously measured the frontal activations of ninety-four pairs of participants using a functional near-infrared spectroscopy (fNIRS)-based hyperscanning technique while they performed a joint Simon task. Behavioral results showed that the Joint Simon Effect (JSE), defined as the RT difference between incongruent and congruent conditions indicating the level of self-other integration between collaborators, was larger in the friend group than in the stranger group. Consistently, the inter-brain neural synchronization (INS) across the dorsolateral and medial parts of the prefrontal cortex was also stronger in the friend group. In addition, INS in the left dorsolateral prefrontal cortex negatively predicted JSE only in the friend group. These results suggest that close interpersonal distance may enhance the shared mental representation among collaborators, which in turn influences their collaborative performance.

Joint action with human and robotic co-actors: Self-other integration is immune to the perceived humanness of the interacting partner

When performing a joint action task, we automatically represent the action and/or task constraints of the co-actor with whom we are interacting. Current models suggest that, not only physical similarity, but also abstract, conceptual features shared between self and the interacting partner play a key role in the emergence of joint action effects. Across two experiments, we investigated the influence of the perceived humanness of a robotic agent on the extent to which we integrate the action of that agent into our own action/task representation, as indexed by the Joint Simon Effect (JSE). The presence (vs. absence) of a prior verbal interaction was used to manipulate robot's perceived humanness. In Experiment 1, using a within-participant design, we had participants perform the joint Go/No-go Simon task with two different robots. Before performing the joint task, one robot engaged in a verbal interaction with the participant and the other robot did not. In Experiment 2, we employed a between-participants design to contrast these two robot conditions as well as a human partner condition. In both experiments, a significant Simon effect emerged during joint action and its amplitude was not modulated by the humanness of the interacting partner. Experiment 2 further showed that the JSE obtained in robot conditions did not differ from that measured in the human partner condition. These findings contradict current theories of joint action mechanisms according to which perceived self-other similarity is a crucial determinant of self-other integration in shared task settings.

Joint spatial-temporal association of response codes (STEARC) effect: Mental timelines embodied interpersonally

A co-action task was used to explore the effect of social interactions on temporal judgements, in comparison with an individual-task condition. In Experiment 1, the co-actors sat either individually (individual condition) or alongside a partner (joint condition) in front of a monitor and then responded to time-related words (e.g. yesterday, tomorrow). In Experiment 2, co-actors sat separately in front of two monitors and categorized the words either individually or jointly. Participants' response times to past- and future-related words in the individual conditions of both experiments had no significant difference. However, in the joint conditions, the responses were faster when the past-time words were mapped toward the participants on the left than when future-time words were mapped toward them. Our data support the existence of a specific mapping between past-time-left space and future-time-right space. This suggests that the two cooperators probably shared a similar mental timeline.

Brain-to-brain synchrony during dyadic action co-representation under acute stress: evidence from fNIRS-based hyperscanning

Unexpected acute stressors may affect our co-representation with other co-actors when completing the joint tasks. The present study adopted the emergent functional near-infrared spectroscopy (fNIRS)-based hyperscanning method to explore the brain-to-brain synchrony when implementing the Joint Simon Task under acute stress induced in the laboratory. The behavioral results reported that the joint Simon effect (JSE) was found in both the stress group and the control group, but the joint Simon effect in the stress group was significantly lessened than the joint Simon effect in the control group, demonstrating that when completing the joint action task in the state of acute stress, women's ability to distinguishing self- from other-related mental representations was improved, and the strength of women's action co-representation was diminished. The fNIRS results showed that when completing the joint Simon task in the state of the acute stress, the brain-to-brain synchrony at the r-TPJ in the stress group was significantly higher than that in the control group, demonstrating that the increased brain-to-brain synchrony at the TPJ may be served as the critical brain-to-brain neural mechanism underlying the joint action task under acute stress.

Association between Reaction Times in the Joint Simon Task and Personality Traits

Joint go and no-go effects (joint Simon effects; JSEs) are considered to have a stimulus-response compatibility effect on joint reaction time tasks (joint Simon task) caused by the presence of other people. Additionally, JSEs are known to be associated with various social factors and are therefore a potential clinical marker for communicative function; however, the relationship with the personality that is associated with communication skills remains unclear. In this study, we focused on the association between JSE and personality traits. Thirty Japanese participants (fifteen women) were recruited. First, personality trait scores were obtained using the Japanese version of the ten-item personality inventory before the experiment. Second, we measured reaction times in the joint Simon task and single go and no-go tasks with the go signal presented on the congruent and incongruent sides. At last, we analyzed the association between reaction times and personality traits by using Spearman's correlation analysis. As a result, we observed two pairs with significant correlations: JSE and neuroticism and short reaction times in the joint condition and agreeableness. In conclusion, we identified potential psychological markers associated with the joint Simon task. These findings may lead to an additional hypothesis regarding the neurobiological mechanisms of JSEs.

Error observation as a window on performance monitoring in social contexts? A systematic review

Living in a social world requires social monitoring, i.e., the ability to keep track of others' actions and mistakes. Here, we demonstrate the good reliability of the behavioral and neurophysiological indexes ascribed to social monitoring. We also show that no consensus exists on the cognitive bases of this phenomenology and discuss three alternative hypotheses: (i) the direct matching hypothesis, postulating that observed errors are processed through automatic simulation; (ii) the attentional hypothesis, considering errors as unexpected events that take resources away from task processing; and (iii) the goal representation hypothesis, which weighs social error monitoring depending on how relevant the other's task is to the observer's goals. To date, evidence on the role played by factors that could help to disentangle these hypotheses (e.g., the human vs. non-human nature of the actor, the error rate, and the reward context) is insufficient, although the goal representation hypothesis seems to receive more support. Theory-driven experimental designs are needed to enlighten this debate and clarify the role of error monitoring during interactive exchanges.

The contextual cueing effect disappears during joint search in preschool children

During preschool years, children's interacting with others increases. One of the involved developmental skills is task co-representation, through which children aged 5 years and older represent a partner's task in a similar way to their own task. In adults, task co-representation makes participants attend to and form memories of objects relevant to both their own task and their partner's task; however, it is unclear whether children can also form such memories. In Experiment 1, we examined the memory facilitation of joint search using a contextual cueing effect paradigm. Children were presented with search displays repeatedly with the same or random layouts and searched and responded to the target either alone (the single group; n = 32; M_age = 73.6 months, range = 61-80) or with their parent (the joint group; n = 32; M_age = 74.3 months, range = 64-81). Results showed that the search with the same layouts was faster than that with the random layouts for the single group, indicating that children form associative memories of target and distractors relevant to their own task. For the joint group, this effect was not statistically different from that of the single group, with exploratory analysis suggesting that it was disrupted. In Experiment 2, children performed the search with a peer (n = 32; M_age = 72.7 months, range = 67-79) and the effect was also not found. Our findings suggest that the self's and partner's tasks are represented but might not be incorporated into associative memory in 5- and 6-year-old children.

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.

Co-actors represent each other's task regularity through social statistical learning

Numerous joint action studies have demonstrated that certain low-level aspects (e.g., stimuli and responses) of a co-actor's task can be automatically and implicitly represented by us as actors, biasing our own task performance in a joint action setup. However, it remains unclear whether individuals also represent more abstract, high-level aspects of a co-actor's task, such as regularity. In the first five experiments, participants participated alongside their co-actors and responded to a mixed shape sequence generated by randomly interleaving two fixed order sequences of shapes in both the pre- and post-test sessions. But different intermediate practice sessions were undergone by participants across experiments. When practicing their own fixed order sequences in a mixed shape sequence, either together with another person (Experiment 1) or alone but informed that their partner was performing the same practice task in a different room (Experiment 4), participants exhibited a learning effect on their co-actors' practiced sequences. This indirect learning effect was absent when one of the co-actors did not participate due to either being removed from the practice (Experiment 2) or sitting still without offering responses (Experiment 3), as well as when the two co-actors practiced together but responded to two distinct properties of stimuli (e.g., colour and shape, respectively), with one having regularity and the other not. Finally, participants exhibited comparable direct learning effects on their own practiced sequences for Experiments 1-5 as when performing the pre-test, practice, and post-test sessions alone for Experiment 6. These results demonstrate that, when practicing together, or even when believing that they are acting together with a partner, co-actors do represent the task regularity of one another through social statistical learning and transfer this learned regularity to subsequent task performances. The present study extends our understanding of co-representation in the joint action context in terms of the more abstract and high-level task features people co-represent, such as a co-actor's task regularity.

Gender composition of pairs influences joint action effect

Research on joint action has demonstrated that individuals are sensitive to a coactor's attentional relation to jointly attend stimuli. It has also been suggested that some features are necessary to resolve the discrimination problem (i.e., self-own and other-own actions). In the present study, we aimed to test whether the gender composition of interacting pairs modulated the joint action effect. Same- (female-female or male-male) and mixed- (female-male) gender pairs performed a joint version of flanker tasks in Experiment 1 (90 participants, 50% males), while in Experiment 2 (154 participants, 50% males) Navon tasks were performed. In Experiment 1, a higher joint flanker effect in same-gender pairs than in mixed-gender pairs, and this joint effect was similar to the classical flanker effect reported by males and females in a classical procedure of the task (70 participants, 50% males). In Experiment 2, the same-gender pairs reported a joint Navon effect, which was reversed in mixed-gender pairs. In conclusion, our findings support how the gender composition of interacting pairs plays a role in joint attentional tasks.

The role of action inhibition for behavioral control in joint action

When two individuals share a task with a common goal, coordinating one's own and the other's actions is pivotal. Inhibition of one's own actions when it is the other's turn to act is assumed to play a crucial role in this process. For instance, in the joint Simon task, two individuals share a two-choice task such that one of them responds to one stimulus type and ignores the stimulus type to which the other responds. Because stimuli can either appear on one's own or on the other's side, stimulus location can conflict with stimulus identity, thus slowing response time. It has previously been shown that such conflict leads to a reduction of the detrimental effects of conflict on immediately upcoming trials both following own responses and even more so following the other's responses. This amplified trial-to-trial adjustment following the other's responses has been assumed to reflect the inhibition of own responses on the other's trials. The present study tested this hypothesis by comparing sequential trial-to-trial adjustments following correct responses and commission errors on which the inhibition of own responses has failed. As expected, adjustments were stronger following the other's correct responses than following own correct responses. Crucially, such amplification of sequential adjustment was not observed following own commission errors on the other's trials. This shows that amplification of sequential adjustments following the other's trials depend on successful inhibition of own responses on these trials and points to a crucial role of response inhibition for behavioral control in joint action.

Abstract and concrete concepts in conversation

Concepts allow us to make sense of the world. Most evidence on their acquisition and representation comes from studies of single decontextualized words and focuses on the opposition between concrete and abstract concepts (e.g., "bottle" vs. "truth"). A significant step forward in research on concepts consists in investigating them in online interaction during their use. Our study examines linguistic exchanges analyzing the differences between sub-kinds of concepts. Participants were submitted to an online task in which they had to simulate a conversational exchange by responding to sentences involving sub-kinds of concrete (tools, animals, food) and abstract concepts (PS, philosophical-spiritual; EMSS, emotional-social, PSTQ, physical-spatio-temporal-quantitative). We found differences in content: foods evoked interoception; tools and animals elicited materials, spatial, auditive features, confirming their sensorimotor grounding. PS and EMSS yielded inner experiences (e.g., emotions, cognitive states, introspections) and opposed PSTQ, tied to visual properties and concrete agency. More crucially, the various concepts elicited different interactional dynamics: more abstract concepts generated higher uncertainty and more interactive exchanges than concrete ones. Investigating concepts in situated interactions opens new possibilities for studying conceptual knowledge and its pragmatic and social aspects.

Wearing the face mask affects our social attention over space

Recent studies suggest that covering the face inhibits the recognition of identity and emotional expressions. However, it might also make the eyes more salient, since they are a reliable index to orient our social and spatial attention. This study investigates (1) whether the pervasive interaction with people with face masks fostered by the COVID-19 pandemic modulates the processing of spatial information essential to shift attention according to other's eye-gaze direction (i.e., gaze-cueing effect: GCE), and (2) whether this potential modulation interacts with motor responses (i.e., Simon effect). Participants were presented with face cues orienting their gaze to a congruent or incongruent target letter location (gaze-cueing paradigm) while wearing a surgical mask (Mask), a patch (Control), or nothing (No-Mask). The task required to discriminate the identity of the lateralized target letters by pressing one of two lateralized response keys, in a corresponding or a non-corresponding position with respect to the target. Results showed that GCE was not modulated by the presence of the Mask, but it occurred in the No-Mask condition, confirming previous studies. Crucially, the GCE interacted with Simon effect in the Mask and Control conditions, though in different ways. While in the Mask condition the GCE emerged only when target and response positions corresponded (i.e., Simon-corresponding trials), in the Control condition it emerged only when they did not correspond (i.e., Simon-non-corresponding trials). These results indicate that people with face masks induce us to jointly orient our visual attention in the direction of the seen gaze (GCE) in those conditions resembling (or associated with) a general approaching behavior (Simon-corresponding trials). This is likely promoted by the fact that we tend to perceive wearing the mask as a personal safety measure and, thus, someone wearing the face mask is perceived as a trustworthy person. In contrast, people with a patch on their face can be perceived as more threatening, therefore inducing a GCE in those conditions associated with a general avoidance behavior (Simon-non-corresponding trials).

Reaction time coupling in a joint stimulus-response task: A matter of functional actions or likable agents?

Shaping one owns actions by observing others’ actions is driven by the deep-rooted mechanism of perception-action coupling. It typically occurs automatically, expressed as for example the unintentional synchronization of reaction times in interactive games. Theories on perception-action coupling highlight its benefits such as the joint coordination of actions to cooperatively perform tasks properly, the learning of novel actions from others, and the bonding with likable others. However, such functional aspects and how they shape perception-action coupling have never been compared quantitatively. Here we tested a total of hundred-fifteen participants that played a stimulus-response task while, in parallel, they observed videos of agents that played the exact same task several milliseconds in advance. We compared to what degree the reaction times of actions of agents, who varied their behavior in terms of functionality and likability in preceding prisoner dilemma games and quizzes, shape the reaction times of human test participants. To manipulate functionality and likability, we varied the predictability of cooperative behavior and correctness of actions of agents, respectively, resulting in likable (cooperative), dislikable (uncooperative), functional (correct actions), and dysfunctional (incorrect actions) agents. The results of three experiments showed that the participants’ reaction times correlated most with the reaction times of agents that expressed functional behavior. However, the likability of agents had no effects on reaction time correlations. These findings suggest that, at least in the current computer task, participants are more likely to adopt the timing of actions from people that perform correct actions than from people that they like.

A Machine Learning Approach for Detecting Cognitive Interference Based on Eye-Tracking Data

The Stroop test evaluates the ability to inhibit cognitive interference. This interference occurs when the processing of one stimulus characteristic affects the simultaneous processing of another attribute of the same stimulus. Eye movements are an indicator of the individual attention load required for inhibiting cognitive interference. We used an eye tracker to collect eye movements data from more than 60 subjects each performing four different but similar tasks (some with cognitive interference and some without). After the extraction of features related to fixations, saccades and gaze trajectory, we trained different Machine Learning models to recognize tasks performed in the different conditions (i.e., with interference, without interference). The models achieved good classification performances when distinguishing between similar tasks performed with or without cognitive interference. This suggests the presence of characterizing patterns common among subjects, which can be captured by machine learning algorithms despite the individual variability of visual behavior.

Spatial auditory presentation of a partner's presence induces the social Simon effect

Social presence is crucial for smooth communications in virtual reality (VR). Current telecommunication systems rarely submit spatial auditory information originating from remote people. However, such information may enhance social presence in VR. In this study, we constructed a dynamic binaural synthesis system and investigated the effect of spatial auditory information of a remote partner on a participant's behavior using the social Simon effect (SSE). The SSE is a spatial stimulus-response compatibility effect between two persons. The SSE occurs when one perceives that their partner is present. Several studies have confirmed the SSE in actual environments. We presented partner sounds diotically (i.e., without spatial information) to one group or binaurally (i.e., with spatial information) to another group through headphones without providing visual information about the partner. The results showed that the SSE was induced only in the binaural group in the current auditory VR (Experiment 1), whereas both groups exhibited the SSE in an actual environment (Experiment 2). These results suggest that the auditory spatial information of remote people is sufficient to induce the SSE and has a potential to enhance social presence.

Joint Simon effect in movement trajectories

In joint action literature it is often assumed that acting together is driven by pervasive and automatic process of co-representation, that is, representing the co-actor's part of the task in addition to one's own. Much of this research employs joint stimulus-response compatibility tasks varying the stimuli employed or the physical and social relations between participants. In this study we test the robustness of co-representation effects by focusing instead on variation in response modality. Specifically, we implement a mouse-tracking version of a Joint Simon Task in which participants respond by producing continuous movements with a computer mouse rather than pushing discrete buttons. We have three key findings. First, in a replication of an earlier study we show that in a classical individual Simon Task movement trajectories show greater curvature on incongruent trials, paralleling longer response times. Second, this effect largely disappears in a Go-NoGo Simon Task, in which participants respond to only one of the cues and refrain from responding to the other. Third, contrary to previous studies that use button pressing responses, we observe no overall effect in the joint variants of the task. However, we also detect a notable diversity in movement strategies adopted by the participants, with some participants showing the effect on the individual level. Our study casts doubt on the pervasiveness of co-representation, highlights the usefulness of mouse-tracking methodology and emphasizes the need for looking at individual variation in task performance.

Color me impressed: A partner's target feature captures visual attention

Attending to a target is more difficult in the presence of a salient distractor. The present study investigated whether social value can modulate the extent to which distractors capture attention. Two participants sitting side-by-side performed a visual search task in cooperative and competitive conditions. Search displays contained either both targets, one target and a neutral stimulus or an ambiguous and a neutral stimulus. Results showed that agents took longer to respond to targets presented together with the partner's target compared to a neutral stimulus of equal salience. Agents also produced more false alarms in response to stimuli whose color lay between their own and the partner's target color compared to stimuli lying between the colors of their target and a neutral stimulus. These results suggest that stimuli with features relevant to a partner can capture attention more than neutral but equally salient stimuli, indicating that social value affects selective attention in a similar way as task goals and selection history.

Number to me, space to you: Joint representation of spatial-numerical associations

Recent work has shown that number concepts activate both spatial and magnitude representations. According to the social co-representation literature which has shown that participants typically represent task components assigned to others together with their own, we asked whether explicit magnitude meaning and explicit spatial coding must be present in a single mind, or can be distributed across two minds, to generate a spatial-numerical congruency effect. In a shared go/no-go task that eliminated peripheral spatial codes, we assigned explicit magnitude processing to participants and spatial processing to either human or non-human co-agents. The spatial-numerical congruency effect emerged only with human co-agents. We demonstrate an inter-personal level of conceptual congruency between space and number that arises from a shared conceptual representation not contaminated by peripheral spatial codes. Theoretical implications of this finding for numerical cognition are discussed.

Your action does matter to me: Examining the role of the co-actor's action-effects in resolving the self-other discrimination problem

Sharing a task with another person can introduce the need to discriminate representations that refer to our own action from that of the other person's. The current understanding is that information about the stimulus event drives the self-other discrimination process, as it promotes (via the reactivation of feature codes) the representation that encodes the corresponding action. However, this mechanistic explanation relies on experimental situations in which stimulus event information (e.g., spatial location) is always and directly available. Thus, it remains unclear whether and how we could successfully discriminate between self- and other related action representations in the absence of such information. The present study addressed this unanswered question using a novel joint Simon task-based paradigm. We report the results of three experiments in which we manipulated the availability of stimulus event information into the contralateral space. Our findings demonstrate that participants are able to compensate for the absence of stimulus event information by relying on temporal features of their co-actor's action-effects (Experiment 1). Even more surprising was that participants continued to monitor the temporal features of their co-actor's actions even when given a verbal signal by their co-actor (Experiments 2a), or full access to the common workspace (Experiment 2b). Our results are strong evidence that the representation of actions is not purely stimulus driven. They suggest that the temporal dimension of the other person's actions is able to drive the self-other discrimination process, in the same way as other perceptual dimensions and feature codes that are shared with the stimulus event.

How vertical elevation affects self-other integration as measured by the joint Simon effect

Earlier findings suggest that positions of power decrease self-other integration and increase psychological distance to others. Until now, however, evidence for this relation rests exclusively on subjective measures. The current research instead employed a vertical joint Simon task to measure self-other integration. This task assesses the extent to which people represent their own actions in reference to their co-actor's, also referred to as the joint Simon effect. Building on cultural associations between power and vertical elevation, we manipulated whether participants were in an elevated (high-power) or lower (low-power) seating position. Experiments 1a and 1b reanalyzed existing datasets and found that elevated (vs. lower) seating position decreased the joint Simon effect, consistent with predictions. Experiment 2 provides a high-powered replication of this finding. Yet, further analyses revealed that feelings of power - measured as a manipulation check and indeed demonstrating that the manipulation was successful - did not mediate or moderate the effect of seating position on the joint Simon effect. Therefore, it is possible that the effect of seating elevation was driven through other aspects of that manipulation than feelings of power. We discuss these and suggest ways to test these alternative explanations.

Negative affordance effect: automatic response inhibition triggered by handle orientation of non-target object

Habituated response tendency associated with affordance of an object is automatically inhibited if this affordance cue is extracted from a non-target object. This study presents two go/no-go experiments investigating whether this response control operates in response selection processes and whether it is linked to conflict-monitoring mechanisms. In the first experiment, the participants performed responses with one hand, and in the second experiment, with two hands. In addition, both experiments consisted of two blocks with varying frequency of go conditions (25%-go vs. 75%-go). The non-target-related response inhibition effect was only observed in Experiment 2 when the task required selecting between two hands. Additionally, the results did not reveal patterns typically related to conflict monitoring when go-frequency is manipulated and when a stimulus-response compatibility effect is examined relative to congruency condition of the previous trial. The study shows that the non-target-related response inhibition assists hand selection and is relatively resistant to conflict-monitoring processes.

The relevance of signal timing in human-robot collaborative manipulation

To achieve a seamless human-robot collaboration, it is crucial that robots express their intentions without perturbating or interrupting the task that a human partner is performing at that moment. Although it has not received much attention so far, this issue is important when robots assist humans in physical and manipulation tasks. The main question addressed here is whether there is a more appropriate time to inform a human partner that a robot is requesting to pass them an object. This question is posed in a reference scenario where human individuals are involved in a continuous pick-and-place task that cannot be interrupted. Our findings showed that providing a cue at the beginning of a reach-to-grasp movement could severely interfere with the ongoing human action, increasing the number of errors made by humans, slowing down and degrading the smoothness of their arm movement, and deflecting their gaze. These disruptive interferences strongly decreased, until they disappeared, when the robot provided the cue to the human partners shortly after the participants picked up an object, identifying this as the best signaling timing. The results of this work showed how the signaling timing may have a decisive influence on the performances of the human-robot teamwork and contribute to understanding the mechanisms underpinning the phenomenon of cognitive-motor interference in humans.

The Underlying neural mechanisms of interpersonal situations on collaborative ability: A hyperscanning study using functional near-infrared spectroscopy

The collaborative ability to coordinate an individual with others is critical to performance of joint actions. Prior studies found that different types of interpersonal situations have more or less impact on the collaborative ability of joint actions, but the results are controversial. To clarify the influence of interpersonal situations on collaborative ability, we adopted the joint Simon task, a choice-reaction task that two people perform together. Functional near-infrared spectroscopy (fNIRS) was used to study the neural mechanisms of interpersonal situations on collaborative ability and task performance under payoffs that fostered competition or cooperation. The fNIRS results showed that significant inter-brain neural synchronization (INS) occurred in the bilateral inferior parietal lobule (IPL) for both situations. Moreover, for the competition situation, the pairs also shown a significant INS in the right IPL. These results imply that the bilateral IPL is involved in cooperation and competition due to involvement of common concern and understanding of intention. The right IPL may be more crucial for competition because of the psychological resources involved in distinguishing self and others. Eventually, the INS in competition was better than in the other situations, correlating with higher performance of the joint task as well.

When two actors perform different tasks: Still no evidence for shared task-sets in joint task switching

Two different variations of joint task switching led to different conclusions as to whether co-acting individuals share the same task-sets. The present study aimed at bridging this gap by replicating the version in which two actors performed two different tasks. Experiment 1 showed switch costs across two actors in a joint condition, which agreed with previous studies, but also yielded even larger switch costs in a solo condition, which contradicted the claim that actors represent an alternative task as their own when it is carried out by the co-actor but not when no one carries it out. Experiments 2 and 3 further examined switch costs in the solo condition with the aim to rule out possible influences of task instructions for and experiences with the other task that was not assigned to the actor. Before participants were instructed on the second of the two tasks, switch costs were still obtained without a co-actor when explicit task names (“COLOUR” and “SHAPE”) served as go/nogo signals (Experiment 2), but not when arbitrary symbols (“XXXX” and “++++”) served as go/nogo signals (Experiment 3). The results thus imply that switch costs depend on participants’ knowledge of task cues being assigned to two different tasks, but not on whether the other task is performed by a co-actor. These findings undermine the assumption that switch costs in the joint conditions reflect shared task-sets between co-actors in this procedure.

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.

Not so social after all: Video-based acquisition of observational stimulus-response bindings

Merely observing how another person responds to a stimulus results in incidental stimulus-response (SR) bindings in memory. These observationally acquired SR bindings can be retrieved on a later occasion. Retrieval will bias current behavioral response tendencies towards re-execution of the observed response. Previous demonstrations of this effect endorsed a dyadic interaction paradigm in which two co-actors respond in alternating fashion. The present paper investigates a video-based version of the observational SR binding task in which videotaped responses are observed on screen. Whereas findings from the dyadic paradigm indicate that retrieval of observationally acquired SR bindings is modulated by social relevance, the video-based paradigm is not influenced by social moderators. Data of four experiments show that manipulations of visual perspective, natural and artificial group membership had no modulatory effect on retrieval of observationally acquired SR bindings in the video-based paradigm. The absence of any socially modulated effect in the video-based paradigm is supported by Bayesian statistics in favor of the null hypothesis. Data from a fifth experiment suggests that observational SR binding and retrieval effects in the video-based paradigm reflect the influence of spatial attention allocated towards response keys of observed responses. Implications for the suitability of both paradigms to study observational learning and joint action phenomena are discussed.

Reciprocity and alignment: quantifying coupling in dynamic interactions

Recent accounts of social cognition focus on how we do things together, suggesting that becoming aligned relies on a reciprocal exchange of information. The next step is to develop richer computational methods that quantify the degree of coupling and describe the nature of the information exchange. We put forward a definition of coupling, comparing it to related terminology and detail, available computational methods and the level of organization to which they pertain, presenting them as a hierarchy from weakest to richest forms of coupling. The rationale is that a temporally coherent link between two dynamical systems at the lowest level of organization sustains mutual adaptation and alignment at the highest level. Postulating that when we do things together, we do so dynamically over time and we argue that to determine and measure instances of true reciprocity in social exchanges is key. Along with this computationally rich definition of coupling, we present challenges for the field to be tackled by a diverse community working towards a dynamic account of social cognition.

Coordinating attention requires coordinated senses

From playing basketball to ordering at a food counter, we frequently and effortlessly coordinate our attention with others towards a common focus: we look at the ball, or point at a piece of cake. This non-verbal coordination of attention plays a fundamental role in our social lives: it ensures that we refer to the same object, develop a shared language, understand each other's mental states, and coordinate our actions. Models of joint attention generally attribute this accomplishment to gaze coordination. But are visual attentional mechanisms sufficient to achieve joint attention, in all cases? Besides cases where visual information is missing, we show how combining it with other senses can be helpful, and even necessary to certain uses of joint attention. We explain the two ways in which non-visual cues contribute to joint attention: either as enhancers, when they complement gaze and pointing gestures in order to coordinate joint attention on visible objects, or as modality pointers, when joint attention needs to be shifted away from the whole object to one of its properties, say weight or texture. This multisensory approach to joint attention has important implications for social robotics, clinical diagnostics, pedagogy and theoretical debates on the construction of a shared world.

Metacontrol and joint action: how shared goals transfer from one task to another?

In most of our daily activities and in team sports, we interact with other individuals and do not act in isolation. Using a social variant of the standard two-choice Simon task, this study aims to test if competitive/cooperative processing modes (i.e., metacontrol states) change the degree of bodily self-other integration between two persons in joint action. In addition, and more exploratory the study tested if this effect depends on a shared group experience with the partner. Two participants shared a visual Simon task, so that each person basically performed complementary parts of the task, which transfers the paradigm into a go/no-go Simon task for each person. Before running this joint Simon task, we set both participants either in a competitive or a cooperative control state by means of a dyadic game, a manipulation aimed at testing possible goal transfer across tasks. We found significant joint Simon effects for participants who were in a competitive state and for participants who were in a cooperative state. The joint Simon effect for participants being in a competitive state was significantly smaller than for participants being in a cooperative state. When experiencing the goal induction together with the partner, the joint Simon effect was significantly decreased as when the induction was performed alone. Both effects (metacontrol state induction and shared experience) seem to be statistically independent of each other. In line with predictions of metacontrol state theory, our study indicated that abstract cognitive goal states can be transferred from one task to another task, able to affect the degree of bodily self-other integration across different task situations.

Effect of perceived interpersonal closeness on the joint Simon effect in adolescents and adults

Here, we explored the role of perceived interpersonal closeness in joint action using the joint Simon task in adolescents and adults. In a two-choice reaction time task, spatially assigned responses to non-spatial stimulus features are faster when the stimulus and response are in congruent locations than not. This phenomenon is called Simon effect and is absent or strongly attenuated when a participant responds to only one of the stimuli. However, the effect reappears when two participants carry out the same go/no-go tasks cooperatively. This re-emergence of the Simon effect in joint action is called the joint Simon effect (JSE). In this study, we first replicated the standard and joint Simon effects in adolescents (n = 43), as well as adults (n = 39) with similar magnitude of the effects in the two age groups. The magnitude of the JSE was positively correlated with the level of closeness as measured by Inclusion of Other in the Self scale. This correlation was not significantly different in adolescents (n = 73) compared to adults (n = 71). Our findings show that joint action is sensitive to the social factor such as interpersonal closeness, and the underlying mechanisms are already mature by adolescence.

Predictive person models elicit motor biases: The face-inhibition effect revisited

Using an established paradigm, we tested whether people derive motoric predictions about an actor's forthcoming actions from prior knowledge about them and the context in which they are seen. In two experiments, participants identified famous tennis and soccer players using either hand or foot responses. Athletes were shown either carrying out or not carrying out their associated actions (swinging, kicking), either in the context where these actions are typically seen (tennis court, soccer Pitch) or outside these contexts (beach, awards ceremony). Replicating prior work, identifying non-acting athletes revealed the negative compatibility effects: viewing tennis players led to faster responses with a foot than a hand, and vice versa for viewing soccer players. Consistent with the idea that negative compatibility effects result from the absence of a predicted action, these effects were eliminated (or reversed) when the athletes were seen carrying out actions typically associated with them. Strikingly, however, these motoric biases were not limited to In-Context trials but were, if anything, more robust in the Out-of-Context trials. This pattern held even when attention was drawn specifically to the context (Experiment 2). These results confirm that people hold motoric knowledge about the actions that others typically carry out and that these actions are part of perceptual representations that are accessed when those others are re-encountered, possibly in order to resolve uncertainty in person perception.

The effect of co-actor group membership on the social inhibition of return effect

Being part of a group is a crucial factor in human social interaction. In the current study we explored whether group membership affects reflexive automatic cognitive functioning, and specifically the social inhibition of return effect (SIOR; Welsh et al., 2005). SIOR is characterized by slower reaction times (RTs) to a location already searched by another agent. To examine whether group membership modulates SIOR, we recruited Muslim and Jewish students from the University of Haifa to perform a task with either an in-group member or an out-group member. Both IOR and SIOR were suggested to act as a foraging facilitator (Klein, 2000; Welsh et al., 2005). Accordingly, we predicted that the SIOR effect would be larger when performing the task with an in-group member than with an out-group member. The results confirmed our prediction by indicating that the co-actor's group membership modulated the SIOR effect. These findings are consistent with the notion that social factors play a critical role in producing the SIOR effect and provide a novel indication of the influence of social factors such as group membership on basic reflexive cognitive processes.

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.

Embodied self-other overlap in romantic love: a review and integrative perspective

Romantic love has long intrigued scientists in various disciplines. Social-cognitive research has provided ample evidence for overlapping mental representations of self and romantic partner. This overlap between self and romantic partner would contribute to the experience of love and has been found to be a predictor of relationship quality. Self-partner overlap has been mainly documented at the level of conceptual or narrative self, with studies showing confusion between one's own and partner's identity aspects, perspectives, and outcomes. But the self is not restricted to abstract, conceptual representations but also involves body-related representations, which, research has revealed, are linked to social-cognitive processes. In this article, we review the emerging evidence that romantic love involves not only a blurring of conceptual selves but also a reduction of the distinction between self and romantic partner at a bodily level. We discuss the potential function(s) of self-other overlap in romantic relationship at the level of body-related representations and consider possible mechanisms. We conclude with possible future directions to further investigate how romantic love engages embodied self-other representations involved in social interactions.

Social Cognition 2.0: Toward Mechanistic Theorizing

Social cognition emerged in the 1970s and 80s as an attempt to answer social-psychological questions by adopting experimental techniques and theoretical concepts from cognitive psychology. Recently, cognitive psychologists began to build complementary bridges between cognitive and social psychology by showing increasing interest in the cognitive implications of social situations. Here, we take a closer look at the remaining obstacles to join cognitive and social perspectives on human behavior. Using conformity as an example, we attempt to demonstrate that the social-cognition approach has been successful in adopting cognitive concepts and experimental methods, but is still lagging behind with respect to (1) mechanistic theorizing, as it often engages in merely describing phenomena in terms of reasons rather than explaining it in terms of causes and (2) reflecting the sociohistorical context of the phenomenon under investigation. As we try to show, developing mechanistic theories for social phenomena, including the effects of individual differences and their sociohistorical dependencies, is not only possible but necessary to eliminate the boundaries between cognitive and social accounts of human behavior.

The role of the co-actor's response reachability in the joint Simon effect: remapping of working space by tool use

The Simon effect, that is the advantage of the spatial correspondence between stimulus and response locations when stimulus location is task irrelevant, occurs even when the task is performed by two participants, each performing a go/no-go task. This effect, known as the joint Simon effect, does not emerge when participants sit outside each other's peripersonal space, thus suggesting that the presence of an active confederate in peripersonal space might provide a reference for response coding. The present study investigated whether this finding is due to the distance separating the participants and/or to the distance separating each participant and the other agent's response. In two experiments, pairs of participants performed a social detection task sitting outside each other's arm reach, with response keys located close to the participants or outside arm reach. When the response key was located outside the participant's arm reach, he/she could reach it by means of a tool. In Experiment 1, by means of a tool, participants could reach their response key only, while in Experiment 2, they could reach also their co-agent's response key. The joint Simon effect did not emerge when participants could not reach the co-actor's response, while it emerged when they could potentially reach the other participant's response using the tool, but only when turn taking was required. These results may be taken as evidence that the possibility to reach and act upon the co-actor's response key may be at the bases of compatibility effects observed in joint action contexts requiring complementary responses.

Saccadic eye movements do not trigger a joint Simon effect

Although the joint Simon task (JST) has been investigated for more than a decade, its cause is still unclear. According to ideomotor views of action control, action effects are a commonly cited explanation. However, action effects are usually confounded with the actions producing such effects. We combined a JST with eye tracking and asked participants to respond by performing specific saccades. Saccades were followed by visual feedback (central vs. lateral feedback), serving as the action effect. This arrangement allowed us to isolate actions from action effects and, also to prevent each actor from seeing the reciprocal actions of the other actor. In this saccadic JST, we found a significant compatibility effect in the individual setting. The typical enhanced compatibility effect in the joint setting of the JST was absent with central action feedback and even when lateralized visual action feedback was provided. Our findings suggest that the perception of action effects alone might not be sufficient to modulate compatibility effects for eye movements. The presence of a compatibility effect in the individual setting shows the specific requirements of a saccadic compatibility task - the requirement to perform prosaccades to compatible and antisaccades to incompatible target locations. The lack of a difference between compatibility effects in joint and individual settings and the lack of a modulation of the compatibility effect through lateralized visual action feedback shows that the finding of a joint Simon effect that has frequently been reported for manual responses is absent for saccadic responses.

A matter of you versus me? Experiences of control in a joint go/no-go task

When interacting with others, people represent their own as well as their interaction partners' actions. Such joint action representation is essential for action coordination, but may also interfere with action control. We investigated how joint action representations affect experienced control over people's own actions and their interaction partners' actions. Participants performed a joint go/no-go task, which is commonly used to measure to what extent people represent their own actions in spatial reference to their interaction partner (e.g., as 'left' vs. 'right'). After each second trial, participants indicated experienced control over their own action, their interaction partner's action, or over action inhibition. Despite this frequent interruption of the go/no-go task, we found strong evidence for the spatial representation of joint actions. However, this joint action representation did not affect experiences of control. Possible explanations and implications of these findings are discussed.