Let's Move It Together: A Review of Group Benefits in Joint Object Control

Cooperación en el rastreo visual de objetos: resultados preliminares

La cooperación tiene sus costos, pero también sus beneficios. En una tarea de rastreo visual de objetos con tres niveles de dificultad (4, 5 y 6 objetivos a rastrear respectivamente) se comparó el rendimiento de cada individuo en dos condiciones: rendimiento individual vs. rendimiento del individuo como parte de una díada. El propósito del estudio fue explorar si la diferencia en rendimiento entre estas dos condiciones se puede atribuir a la cooperación. Diez estudiantes universitarios respondieron un cuestionario de personalidad de auto informe (Big Five) y realizaron la tarea de rastreo visual de manera individual y como parte de una díada. Las díadas se grabaron en video para identificar las estrategias de comunicación, resolución de problemas y acuerdos en la selección de objetivos. Las díadas mostraron puntajes más altos y tiempos de reacción más lentos en comparación con el rendimiento individual. Los tiempos de reacción más lentos se asociaron positivamente con los intercambios verbales y las estrategias de división del trabajo en la díada. La amabilidad y la extraversión, medidas por el cuestionario de autoinforme, se asociaron positivamente con el acuerdo en la selección de objetivos. La interacción entre los miembros de una díada y sus rasgos de personalidad podrían ser relevantes para comprender la cooperación exitosa y sus costos asociados.

Experimental conditions in which dyads outperform individuals in a task of force produced by two people

When participants control periodic isometric force cycling between two target forces, they more accurately control force in a joint action than in an individual action. In some other studies, however, individuals tend to outperform dyads in joint action. The present study thus examined experimental conditions in which dyads outperformed individuals in a task of force produced by two people. This study consisted of two tasks with two target conditions and three force production conditions. The individual task was performed by one participant, and the joint task was performed by two participants. In absolute and relative target conditions, the participants made continuous, discrete, and periodic isometric pressing movements with the index finger. Although no difference was seen in force error between tasks in the continuous condition, the joint task had a smaller error than the individual task in the two other conditions. The joint task had a smaller variable force than the individual task in the periodic conditions, but no difference was seen in force variability between tasks in the two other conditions. Participants mainly controlled force in both tasks in the continuous condition. In the periodic or discrete condition at a prescribed interval, however, participants had to control both force and timing in the individual task, and muscle force must be mainly controlled to compensate for force errors by synchronizing interpersonal force outputs in the joint task. Thus, dyads can reduce the dimensionality of the control problem because they can synchronize their action which provides timing information.

Joint control of visually guided actions involves concordant increases in behavioural and neural coupling

It is often necessary for individuals to coordinate their actions with others. In the real world, joint actions rely on the direct observation of co-actors and rhythmic cues. But how are joint actions coordinated when such cues are unavailable? To address this question, we recorded brain activity while pairs of participants guided a cursor to a target either individually (solo control) or together with a partner (joint control) from whom they were physically and visibly separated. Behavioural patterns revealed that joint action involved real-time coordination between co-actors and improved accuracy for the lower performing co-actor. Concurrent neural recordings and eye tracking revealed that joint control affected cognitive processing across multiple stages. Joint control involved increases in both behavioural and neural coupling - both quantified as interpersonal correlations - peaking at action completion. Correspondingly, a neural offset response acted as a mechanism for and marker of interpersonal neural coupling, underpinning successful joint actions.

Coordination effort in joint action is reflected in pupil size

Humans often perform visual tasks together, and when doing so, they tend to devise division of labor strategies to share the load. Implementing such strategies, however, is effortful as co-actors need to coordinate their actions. We tested if pupil size - a physiological correlate of mental effort - can detect such a coordination effort in a multiple object tracking task (MOT). Participants performed the MOT task jointly with a computer partner and either devised a division of labor strategy (main experiment) or the labor division was already pre-determined (control experiment). We observed that pupil sizes increase relative to performing the MOT task alone in the main experiment while this is not the case in the control experiment. These findings suggest that pupil size can detect a rise in coordination effort, extending the view that pupil size indexes mental effort across a wide range of cognitively demanding tasks.

Dyadic and triadic search: Benefits, costs, and predictors of group performance

In daily life, humans often perform visual tasks, such as solving puzzles or searching for a friend in a crowd. Performing these visual searches jointly with a partner can be beneficial: The two task partners can devise effective division of labor strategies and thereby outperform individuals who search alone. To date, it is unknown whether these group benefits scale up to triads or whether the cost of coordinating with others offsets any potential benefit for group sizes above two. To address this question, we compare participants' performance in a visual search task that they perform either alone, in dyads, or in triads. When the search task is performed jointly, co-actors receive information about each other's gaze location. After controlling for speed-accuracy trade-offs, we found that triads searched faster than dyads, suggesting that group benefits do scale up to triads. Moreover, we found that the triads' divided the search space in accordance with the co-actors' individual search performances but searched less efficiently than dyads. We also present a linear model to predict group benefits, which accounts for 70% of the variance. The model includes our experimental factors and a set of non-redundant predictors, quantifying the similarities in the individual performances, the collaboration between co-actors, and the estimated benefits that co-actors would attain without collaborating. Overall, the present study demonstrates that group benefits scale up to larger group sizes, but the additional gains are attenuated by the increased costs associated with devising effective division of labor strategies.

Neurophysiological correlates of collective perceptual decision-making

Humans frequently perform tasks collaboratively in daily life. Collaborating with others may or may not result in higher task performance than if one were to complete the task alone (i.e., a collective benefit). A recent study on collective benefits in perceptual decision-making showed that dyad members with similar individual performances attain collective benefit. However, little is known about the physiological basis of these results. Here, we replicate this earlier work and also investigate the neurophysiological correlates of decision-making using EEG. In a two-interval forced-choice task, co-actors individually indicated presence of a target stimulus with a higher contrast and then indicated their confidence on a rating scale. Viewing the individual ratings, dyads made a joint decision. Replicating earlier work, we found a positive correlation between the similarity of individual performances and collective benefit. We analyzed event-related potentials (ERPs) in three phases (i.e., stimulus onset, response and feedback) using explorative cluster mass permutation tests. At stimulus onset, ERPs were significantly linearly related to our manipulation of contrast differences, validating our manipulation of task difficulty. For individual and joint responses, we found a significant centro-parietal error-related positivity for correct versus incorrect responses, which suggests that accuracy is already evaluated at the response level. At feedback presentation, we found a significant late positive fronto-central potential elicited by incorrect joint responses. In sum, these results demonstrate that response- and feedback-related components elicited by an error-monitoring system differentially integrate conflicting information exchanged during the joint decision-making process.

Force asymmetry deteriorates complementary force production during joint action

The present study aimed to determine the effects of force asymmetry on interpersonal force production. This study consisted of an individual task executed by one participant at a time in a pair, and three joint tasks executed by two participants simultaneously under conditions of 1:1, 1:0.75, and 1:0.5. Two individuals produced discrete forces at the same time so that the sum of forces they produced was the target force in the joint task. Under the 1:1 condition, the target force was the sum of the maximum voluntary contraction (MVC) produced by the index finger of each participant × 0.1 (10% MVC). Under the 1:0.75 condition, the investigators manipulated the force produced by only one of the pair, for example, B, but not A. The feedback was also scaled as a result. The target force was the MVC of participant A + the MVC of participant B × 0.75 × 0.1. Similarly, the target force under the 1:0.5 condition was the MVC of participant A + the MVC of participant B × 0.5 × 0.1. The present study found that forces produced by pairs were negatively correlated and the correlation value was higher under the 1:1 condition than the 1:0.75 and 1:0.5 conditions. The absolute error was smaller under the 1:1 condition than the 1:0.5 condition. Complementary force production was attenuated and the error increased as differences between forces produced by two participants increased. Thus, asymmetry of forces produced by pairs deteriorated complementary force production and interpersonal performance.

The Social Situation Affects How We Process Feedback About Our Actions

Humans achieve their goals in joint action tasks either by cooperation or competition. In the present study, we investigated the neural processes underpinning error and monetary rewards processing in such cooperative and competitive situations. We used electroencephalography (EEG) and analyzed event-related potentials (ERPs) triggered by feedback in both social situations. 26 dyads performed a joint four-alternative forced choice (4AFC) visual task either cooperatively or competitively. At the end of each trial, participants received performance feedback about their individual and joint errors and accompanying monetary rewards. Furthermore, the outcome, i.e., resulting positive, negative, or neutral rewards, was dependent on the pay-off matrix, defining the social situation either as cooperative or competitive. We used linear mixed effects models to analyze the feedback-related-negativity (FRN) and used the Threshold-free cluster enhancement (TFCE) method to explore activations of all electrodes and times. We found main effects of the outcome and social situation, but no interaction at mid-line frontal electrodes. The FRN was more negative for losses than wins in both social situations. However, the FRN amplitudes differed between social situations. Moreover, we compared monetary with neutral outcomes in both social situations. Our exploratory TFCE analysis revealed that processing of feedback differs between cooperative and competitive situations at right temporo-parietal electrodes where the cooperative situation elicited more positive amplitudes. Further, the differences induced by the social situations were stronger in participants with higher scores on a perspective taking test. In sum, our results replicate previous studies about the FRN and extend them by comparing neurophysiological responses to positive and negative outcomes in a task that simultaneously engages two participants in competitive and cooperative situations.