Specifying social cognitive processes with a social dual-task paradigm

How Social and Refractory Is the Social Psychological Refractory Period?

Abstract. The social psychological refractory period (PRP) effect refers to an increase in RT to the second of two successive stimuli when another person responds to the first stimulus (shared dual-task condition) rather than when a single person responds to both stimuli (individual dual-task condition). We investigated (a) whether a social PRP effect would occur without explicit instruction concerning task priority and (b) whether there are crosstalk effects in the shared dual-task situation. We observed a strong PRP effect together with a small crosstalk effect in the individual dual-task condition, but in the shared dual-task condition both effects were absent. These findings suggest that the explicit instruction to perform responses in a fixed order is necessary to obtain the social PRP effect. In the individual dual-task condition, sequential processing can be seen as a means to reduce or prevent crosstalk effects, which is not necessary in the shared dual-task condition.

The Medial Frontal Cortex Mediates Self-Other Discrimination in the Joint Simon Task

Abstract. Interacting with other individuals confronts cognitive control systems with the problem of how to distinguish between self-generated (internally triggered) and other-generated (externally triggered) action events. Recent neuroscience studies identified two core brain regions, the anterior medial frontal cortex (aMFC) and the right temporo-parietal junction (rTPJ), to be potentially involved in resolving this problem either by enhancing self-generated versus other-generated event representations (via aMFC) and/or by inhibiting event representations that are externally triggered (via rTPJ). Using transcranial direct current stimulation (tDCS), we investigated the role of the aMFC and the rTPJ for the online control of self-generated versus other-generated event representations in a joint Simon task. In two experimental sessions, participants received anodal, cathodal, or sham tDCS (1 mA intensity applied for 20 min), while performing an auditory joint Simon task. In addition to a general performance enhancement during cathodal (inhibitory) and anodal (excitatory) stimulation with increased practice, we found a significantly increased joint Simon effect (JSE) during cathodal stimulation of the aMFC (Experiment 1), as compared to sham stimulation. No modulation of the JSE was found during stimulation of the rTPJ (Experiment 2). By enhancing self-generated event representations the aMFC seems to be crucially involved in resolving the self-other discrimination problem in the joint Simon task.

Movement priming of EEG/MEG brain responses for action-words characterizes the link between language and action

Activation in sensorimotor areas of the brain following perception of linguistic stimuli referring to objects and actions has been interpreted as evidence for strong theories of embodied semantics. Although a large number of studies have demonstrated this “language-to-action” link, important questions about how activation in the sensorimotor system affects language performance (“action-to-language” link) are yet unanswered. As several authors have recently pointed out, the debate should move away from an “embodied or not” focus, and rather aim to characterize the functional contributions of sensorimotor systems to language processing in more detail. For this purpose, we here introduce a novel movement priming paradigm in combination with electro- and magnetoencephalography (EEG/MEG), which allows investigating effects of motor cortex pre-activation on the spatio-temporal dynamics of action-word evoked brain activation. Participants initiated experimental trials by either finger- or foot-movements before executing a two alternative forced choice task employing action-words. We found differential brain activation during the early stages of subsequent hand- and leg-related word processing, respectively, albeit in the absence of behavioral effects. Distributed source estimation based on combined EEG/MEG measurements revealed that congruency effects between effector type used for response initiation (hand or foot) and action-word category (hand- or foot-related) occurred not only in motor cortex, but also in a classical language comprehension area, posterior superior temporal cortex, already 150 msec after the visual presentation of the word stimulus. This suggests that pre-activation of hand- and leg-motor networks may differentially facilitate the ignition of semantic cell assemblies for hand- and leg-related words, respectively. Our results demonstrate the usefulness of movement priming in combination with neuroimaging to functionally characterize the link between language and sensorimotor systems.

Joint action changes valence-based action coding in an implicit attitude task

Recent studies suggest that co-acting with another person induces a problem to discriminate between one's own and the other's actions which can be resolved by emphasizing action features that discriminate best between both persons' actions in a given task context. Mostly, overt action features like the spatial position of responses have been suggested as discriminating action features. In the present study, we tested whether non-externally perceivable, covert action features can be used for resolving the action discrimination problem during joint action. Therefore, we compared task performance between a joint and an individual version of the Go/Nogo Association Task, a task requiring the association of a valence to the response. We found a larger implicit attitude effect in the joint than in the individual setting for person-related (self and other, Experiment 1) as well as for non-person-related attitude objects (fruit and insect, Experiment 2) suggesting that the weight of valence information is increased in the internal coding of responses when valence discriminates between both responses. In contrast, we found a smaller implicit attitude effect in a person present setting than an individual setting (Experiment 3) indicating that the enhanced implicit attitude effect observed in the joint settings of Experiments 1 and 2 is not due to social facilitation. Our results suggest that action discrimination during joint action can rely on covert action features. The results are in line with the referential coding account, and specify the kind of action features that are represented when sharing a task with another person.

The role of attention in a joint-action effect

The most common explanation for joint-action effects has been the action co-representation account in which observation of another's action is represented within one's own action system. However, recent evidence has shown that the most prominent of these joint-action effects (i.e., the Social Simon effect), can occur when no co-actor is present. In the current work we examined whether another joint-action phenomenon (a movement congruency effect) can be induced when a participant performs their part of the task with a different effector to that of their co-actor and when a co-actor's action is replaced by an attention-capturing luminance signal. Contrary to what is predicted by the action co-representation account, results show that the basic movement congruency effect occurred in both situations. These findings challenge the action co-representation account of this particular effect and suggest instead that it is driven by bottom-up mechanisms.

Group membership affects spontaneous mental representation: failure to represent the out-group in a joint action task

Predicting others' actions is crucial to successful social interaction. Previous research on joint action, based on a reaction-time paradigm called the Joint Simon Task, suggests that successful joint action stems from the simultaneous representation of the self with the other. Performance on this task provides a read-out of the degree of intrusion from a partner that participants experience from acting jointly compared to acting alone, which in turn is a measure of the degree to which participants mentally represent their co-actors during the task. To investigate the role of perceived group membership in this type of joint action and its influence on the representation of others, we first subjected participants to a minimal group paradigm while manipulating differences in social competition. We then asked participants to do the Joint Simon Task in pairs with an in-group or out-group member. Only participants who acted with an "in-group" partner on the joint task showed altered reaction times compared to when acting alone, presumably a change caused by the simultaneous and automatic representation of their in-group partner. In contrast, participants who acted with an out-group partner were unaffected in their reactions when doing the joint task, showing no evidence of representation of their out-group partner. This effect was present in both the high-competition and low-competition conditions, indicating that the differential effects of group membership on representation during joint action were driven by perceived group membership and independent of the effects of social competition. We concluded that participants failed to represent out-group members as socially relevant agents not based on any personality or situational characteristics, but in reaction only to their status as "other". In this way group membership appears to affect cognition on a very immediate and subconscious level.

Visual experience determines the use of external reference frames in joint action control

Vision plays a crucial role in human interaction by facilitating the coordination of one's own actions with those of others in space and time. While previous findings have demonstrated that vision determines the default use of reference frames, little is known about the role of visual experience in coding action-space during joint action. Here, we tested if and how visual experience influences the use of reference frames in joint action control. Dyads of congenitally-blind, blindfolded-sighted, and seeing individuals took part in an auditory version of the social Simon task, which required each participant to respond to one of two sounds presented to the left or right of both participants. To disentangle the contribution of external—agent-based and response-based—reference frames during joint action, participants performed the task with their respective response (right) hands uncrossed or crossed over one another. Although the location of the auditory stimulus was completely task-irrelevant, participants responded overall faster when the stimulus location spatially corresponded to the required response side than when they were spatially non-corresponding: a phenomenon known as the social Simon effect (SSE). In sighted participants, the SSE occurred irrespective of whether hands were crossed or uncrossed, suggesting the use of external, response-based reference frames. Congenitally-blind participants also showed an SSE, but only with uncrossed hands. We argue that congenitally-blind people use both agent-based and response-based reference frames resulting in conflicting spatial information when hands are crossed and, thus, canceling out the SSE. These results imply that joint action control functions on the basis of external reference frames independent of the presence or (transient/permanent) absence of vision. However, the type of external reference frames used for organizing motor control in joint action seems to be determined by visual experience.