Individual differences in reading social intentions from motor deviants

Communicative modulations of early action components support the prediction of distal goals

The successful unfolding of many social interactions relies on our capacity to predict other people's action goals, whether these are proximal (i.e., immediate) or distal (i.e., upcoming). The present set of studies asks whether observers can predict the distal goal of two-step action sequences when presented with communicative modulations of the first movement component of the sequence. We conducted three online experiments in which we presented participants with animations of a box moving to a first target location before moving onwards to a final, either near or far, target location. The second movement component and the target locations were occluded. After observing the first movement, participants were asked to select the most likely final target location, i.e., the distal goal of the sequence. Experiment 1 showed that participants relied on the velocity modulations of the first movement to infer the distal goal. The results of Experiment 2 indicated that such predictions of distal goals are possible even when the second movement in the sequence does not contain any velocity information, thus suggesting that the information present in the first movement plays the major role in the process of linking movements to their distal goals. However, Experiment 3 showed that under some circumstances the second movement can also contribute to how observers predict a distal goal. We discuss these results in terms of the underlying simulation processes that enable observers to predict a distal goal from the observation of proximal communicative modulations.

The contribution of eye gaze and movement kinematics to the expression and identification of social intention in object-directed motor actions

The intention to include another person in an interaction (i.e., social intention) is known to influence the spatio-temporal characteristics of motor performances. However, the interplay between these kinematic variations and the social cues provided by eye gaze has not been properly assessed yet. In the present study, we tested whether limiting the access to eye gaze altered the motor-related effects of social intention on motor performances. In a dyadic interaction, the agents' task was to displace a dummy glass to a new position with the intention to fill it themselves (personal intention) or having it filled by the observers facing them (social intention). The observers performed their action only when they were able to identify a social intention in agents' action. The task was performed while having access to observers' eye gaze or not, through the manipulation of an occluder. Results showed an effect of social intention on agents' motor performances, that induced an amplification of the kinematic spatio-temporal parameters. Such amplification was smaller when the observers' eye gaze was not available. In this latter condition, the identification of the social intention in the observed actions was impaired. Altogether, the results suggest that the presence of eye gaze cues contributes significantly to the success of social interaction, by facilitating the expression and the understanding of social intentions through the kinematics of object-directed actions.

Individual differences in cooperative and competitive play strategies

INTRODUCTION

Cooperation and competition are common in social interactions. It is not clear how individual differences in personality may predict performance strategies under these two contexts. We evaluated whether instructions to play cooperatively and competitively would differentially affect dyads playing a Pong video game. We hypothesized that instructions to play cooperatively would result in lower overall points scored and differences in paddle control kinematics relative to when participants were instructed to play competitively. We also predicted that higher scores in prosociality and Sportspersonship would be related to better performance during cooperative than competitive conditions.

METHODS

Pairs of participants played a Pong video game under cooperative and competitive instructions. During competitive trials, participants were instructed to score more points against one another to win the game. During the cooperative trials, participants were instructed to work together to score as few points against one another as possible. After game play, each participant completed surveys so we could measure their trait prosociality and Sportspersonship.

RESULTS

Condition was a significant predictor of where along the paddle participants hit the ball, which controlled ball exit angles. Specifically, during cooperation participants concentrated ball contacts on the paddle towards the center to produce more consistent rebound angles. We found a significant correlation of Sex and the average points scored by participants during cooperative games, competitive games, and across all trials. Sex was also significantly correlated with paddle kinematics during cooperative games. The overall scores on the prosociality and Sportspersonship surveys were not significantly correlated with the performance outcomes in cooperative and competitive games. The dimension of prosociality assessing empathic concern was significantly correlated with performance outcomes during cooperative video game play.

DISCUSSION

No Sportspersonship survey score was able to predict cooperative or competitive game performance, suggesting that Sportspersonship personality assessments are not reliable predictors of cooperative or competitive behaviors translated to a virtual game setting. Survey items and dimensions probing broader empathic concern may be more effective predictors of cooperative and competitive performance during interactive video game play. Further testing is encouraged to assess the efficacy of prosocial personality traits as predictors of cooperative and competitive video game behavior.

The influence of cooperative action intention on object affordance: evidence from the perspective-taking ability of individuals

In complex interactive scenarios, action understanding lies at the heart of social interactions. Nevertheless, the ability to understand action intention may differ among people. The current study distinguished two groups of participants with different social intention-understanding abilities (high and low) based on a perspective-taking task to investigate the influence of social intention on object affordance under conditions of individual and cooperative action intention. In the affordance perception experiment, participants were shown a video with the presenter reaching to grasp an object in different grips and asked to classify objects into kitchen or non-kitchen items by pressing the left- or right-hand button under the two intention conditions. The results showed that the object affordance effects were modulated by the participants' understanding of social intention in the interactive scenarios. Specifically, the object affordance effects were observed only in the high perspective-taking ability group under the condition of cooperative action intention. However, under the condition of individual action intention, object affordance effects were shown in both the high and low perspective-taking ability groups, and the difference between the two groups was not significant. This study suggests that processing of object affordance depends greatly on the contextual correspondence of perception and action and that the understanding of cooperative action intention can affect the activation of object affordance.

The combined effects of motor and social goals on the kinematics of object-directed motor action

Voluntary actions towards manipulable objects are usually performed with a particular motor goal (i.e., a task-specific object-target-effector interaction) and in a particular social context (i.e., who would benefit from these actions), but the mutual influence of these two constraints has not yet been properly studied. For this purpose, we asked participants to grasp an object and place it on either a small or large target in relation to Fitts’ law (motor goal). This first action prepared them for a second grasp-to-place action which was performed under temporal constraints, either by the participants themselves or by a confederate (social goal). Kinematic analysis of the first preparatory grasp-to-place action showed that, while deceleration time was impacted by the motor goal, peak velocity was influenced by the social goal. Movement duration and trajectory height were modulated by both goals, the effect of the social goal being attenuated by the effect of the motor goal. Overall, these results suggest that both motor and social constraints influence the characteristics of object-oriented actions, with effects that combine in a hierarchical way.

Predictable real-time constraints reveal anticipatory strategies of coupled planning in a sequential pick and place task

Planning a sequence of two motor elements is much more than concatenating two independent movements. However, very little is known about the cognitive strategies that are used to perform fluent sequences for intentional object manipulation. In this series of studies, the participants’ task was to reach for and pick to place a wooden cylinder to set it on a place pad of three different diameters, which served to modify terminal accuracy constraints. Participants were required to perform the sequences (1) at their preferred speed or (2) as fast as possible. Action kinematics were recorded with the Qualisys motion-capture system in order to implement a real-time protocol to get participants to engage in a true interactive relation. Results revealed that with low internal constraints (at preferred speed), low coupling between the two elements of the motor sequence was observed, suggesting a step-by-step planning strategy. Under high constraints (at fastest speed), an important terminal accuracy effect back propagated to modify early kinematic parameters of the first element, suggesting strong coupling of the parameters in an encapsulated planning strategy. In Studies 2 and 3, we further manipulated instructions and timing constraints to confirm the importance of time and predictability of external information for coupled planning. These findings overall sustain the hypothesis that coupled planning can take place in a pick and place task when anticipatory strategies are possible. This mode of action planning may be the key reason why motor intention can be read through the observation of micro variations in body kinematics.

What Do Theory-of-Mind Tasks Actually Measure? Theory and Practice

In recent decades, the ability to represent others' mental states (i.e., theory of mind) has gained particular attention in various disciplines ranging from ethology to cognitive neuroscience. Despite the exponentially growing interest, the functional architecture of social cognition is still unclear. In the present review, we argue that not only the vocabulary but also most of the classic measures for theory of mind lack specificity. We examined classic tests used to assess theory of mind and noted that the majority of them do not require the participant to represent another's mental state or, sometimes, any mental state at all. Our review reveals that numerous classic tests measure lower-level processes that do not directly test for theory of mind. We propose that more attention should be paid to methods used in this field of social cognition to improve the understanding of underlying concepts.

What first drives visual attention during the recognition of object-directed actions? The role of kinematics and goal information

The recognition of others' object-directed actions is known to involve the decoding of both the visual kinematics of the action and the action goal. Yet whether action recognition is first guided by the processing of visual kinematics or by a prediction about the goal of the actor remains debated. In order to provide experimental evidence to this issue, the present study aimed at investigating whether visual attention would be preferentially captured by visual kinematics or by action goal information when processing others' actions. In a visual search task, participants were asked to find correct actions (e.g., drinking from glass) among distractor actions. Distractors actions contained grip and/or goal violations and could therefore share the correct goal and/or the correct grip with the target. The time course of fixation proportion on each distractor action has been taken as an indicator of visual attention allocation. Results show that visual attention is first captured by the distractor action with similar goal. Then the withdrawal of visual attention from the action distractor with similar goal suggests a later attentional capture by the action distractor with similar grip. Overall, results are in line with predictive approaches of action understanding, which assume that observers first make a prediction about the actor's goal before verifying this prediction using the visual kinematics of the action.

The Interplay Between Face-to-Face Contact and Feedback on Cooperation During Real-Life Interactions

Cooperation forms the basis of our society and becomes increasingly essential during times of globalization. However, despite technological developments people still prefer to meet face-to-face, which has been shown to foster cooperation. However, what is still unclear is how this beneficial effect depends on what people know about their interaction partner. To examine this question, 58 dyads played an iterated Prisoner’s Dilemma game, sometimes facing each other, sometimes without face contact. Additionally, explicit feedback regarding their decisions was manipulated between dyads. The results revealed that participants were more cooperative when they saw each other compared to when they could not, and when receiving reliable compared to unreliable or no feedback. Contradicting our hypothesis that participants would rely more on nonverbal communication in the absence of explicit information, we observed that the two sources of information operated independently on cooperative behavior. Interestingly, although individuals mostly relied on explicit information if available, participants still cooperated more after their partner defected with face-to-face contact compared to no face-to-face contact. The results of our study have implications for real-life interactions, suggesting that face-to-face contact has beneficial effects on prosocial behavior even if people cannot verify whether their selfless acts are being reciprocated.

The role of perspective in discriminating between social and non-social intentions from reach-to-grasp kinematics

Making correct inferences regarding social and individual intentions may be crucial for successful interactions, especially when we are required to discriminate between cooperative and competitive behaviors. The results of previous studies indicate that reach-to-grasp kinematic parameters may be used to infer the social or individual outcome of a movement. However, the majority of the studies investigated this ability by presenting reach-to-grasp movements from a third-person perspective only. The aim of the present study was to assess whether the ability to recognize the intent associated to a reach-to-grasp movement varies as a function of perspective by manipulating the perspective of observation (second- and third-perspective) within participants. To this end, we presented participants with video clips of models performing a reach-to-grasp movement with different intents. The video clips were recorded both from a lateral view (third-person perspective) and from a frontal view (second-person perspective). After viewing the clips, in two subsequent tasks participants were asked to distinguish between social and non-social intentions by observing the initial phase of the same action recorded from the two different views. Results showed that, when a fast-speed movement was presented from a lateral view, participants were able to predict its social intention. In contrast, when the same movement was observed from a frontal view, performance was impaired. These results indicate that the ability to detect social intentions from motor cues can be biased by the visual perspective of the observer, specifically for fast-speed movements.

Sensorimotor Coarticulation in the Execution and Recognition of Intentional Actions

Humans excel at recognizing (or inferring) another's distal intentions, and recent experiments suggest that this may be possible using only subtle kinematic cues elicited during early phases of movement. Still, the cognitive and computational mechanisms underlying the recognition of intentional (sequential) actions are incompletely known and it is unclear whether kinematic cues alone are sufficient for this task, or if it instead requires additional mechanisms (e.g., prior information) that may be more difficult to fully characterize in empirical studies. Here we present a computationally-guided analysis of the execution and recognition of intentional actions that is rooted in theories of motor control and the coarticulation of sequential actions. In our simulations, when a performer agent coarticulates two successive actions in an action sequence (e.g., "reach-to-grasp" a bottle and "grasp-to-pour"), he automatically produces kinematic cues that an observer agent can reliably use to recognize the performer's intention early on, during the execution of the first part of the sequence. This analysis lends computational-level support for the idea that kinematic cues may be sufficiently informative for early intention recognition. Furthermore, it suggests that the social benefits of coarticulation may be a byproduct of a fundamental imperative to optimize sequential actions. Finally, we discuss possible ways a performer agent may combine automatic (coarticulation) and strategic (signaling) ways to facilitate, or hinder, an observer's action recognition processes.

Facilitation effect of observed motor deviants in a cooperative motor task: Evidence for direct perception of social intention in action

Spatiotemporal parameters of voluntary motor action may help optimize human social interactions. Yet it is unknown whether individuals performing a cooperative task spontaneously perceive subtly informative social cues emerging through voluntary actions. In the present study, an auditory cue was provided through headphones to an actor and a partner who faced each other. Depending on the pitch of the auditory cue, either the actor or the partner were required to grasp and move a wooden dowel under time constraints from a central to a lateral position. Before this main action, the actor performed a preparatory action under no time constraint, consisting in placing the wooden dowel on the central location when receiving either a neutral ("prêt"-ready) or an informative auditory cue relative to who will be asked to perform the main action (the actor: "moi"-me, or the partner: "lui"-him). Although the task focused on the main action, analysis of motor performances revealed that actors performed the preparatory action with longer reaction times and higher trajectories when informed that the partner would be performing the main action. In this same condition, partners executed the main actions with shorter reaction times and lower velocities, despite having received no previous informative cues. These results demonstrate that the mere observation of socially driven motor actions spontaneously influences the low-level kinematics of voluntary motor actions performed by the observer during a cooperative motor task. These findings indicate that social intention can be anticipated from the mere observation of action patterns.