Visuo-motor interference is modulated by task interactivity: A kinematic study

Abstract

Extensive evidence shows that action observation can influence action execution, a phenomenon often referred to as visuo-motor interference. Little is known about whether this effect can be modulated by the type of interaction agents are involved in, as different studies show conflicting results. In the present study, we aimed at shedding light on this question by recording and analyzing the kinematic unfolding of reach-to-grasp movements performed in interactive and noninteractive settings. Using a machine learning approach, we investigated whether the extent of visuo-motor interference would be enhanced or reduced in two different joint action settings compared with a noninteractive one. Our results reveal that the detrimental effect of visuo-motor interference is reduced when the action performed by the partner is relevant to achieve a common goal, regardless of whether this goal requires to produce a concrete sensory outcome in the environment (joint outcome condition) or only a joint movement configuration (joint movement condition). These findings support the idea that during joint actions we form dyadic motor plans, in which both our own and our partner's actions are represented in predictive terms and in light of the common goal to be achieved. The formation of a dyadic motor plan might allow agents to shift from the automatic simulation of an observed action to the active prediction of the consequences of a partner's action. Overall, our results demonstrate the unavoidable impact of others' action on our motor behavior in social contexts, and how strongly this effect can be modulated by task interactivity.

Keywords: Dyadic motor plan; Joint action; Machine learning; Motor cognition; Movement kinematics; Social interaction; Visuo-motor interference.

Fig. 1

Experimental setup. Panel (a) shows a photo of the experimental setup, in which the participant and the confederate keep their hands in their respective starting positions. In front of the two agents are placed the two objects used during the experiment. The objects were designed to be grasped with either a precision grip or a whole hand prehension. The bright area represents the projection area. During the experiment, the projection area was dark. Projections were used only during catch-trials, during error trials, and during the joint outcome condition. Panel (b) shows a schematic (not in scale) representation of the experimental setup. The numbers refer to the order in which the actions were performed during each motor sequence (i.e., trial). Press and release sensible sensors were placed in strategic positions to control for correct performance during each trial

Fig. 2

Classification accuracy during noninteractive, joint movement, and joint outcome conditions. Panel (a) shows a bar plot representing the mean classification accuracies of the 100 SVM-LASSO models performed for each condition. Bars indicate standard deviation (SD). White asterisks denote significant (i.e., above chance) classification accuracies (*p < 0.05; **p < 0.01; ***p < 0.001). Black asterisks denote significant differences between conditions (*p < 0.05; **p < 0.01). Panel (b) shows the confusion matrices corresponding to each condition (rows are the true classes). The three histograms of panel (c) represent, for each condition, the empirical distribution of the classification accuracies obtained from the 1000 SVM-LASSO models computed after the random permutation of labels. For each of the three histograms, the solid line represents the mean classification accuracy obtained from the original models of the corresponding condition. The dashed line indicates 0.5 chance level

Fig. 3

Classification accuracy and kinematic profiles of single kinematic features during each condition. Panel (a) shows, for each of the four relevant (i.e., significantly discriminative) kinematic features, a bar plot representing the mean classification accuracies of the 1000 SVM-LASSO models performed for each condition. Bars indicate standard deviation (SD). White asterisks denote significant (i.e., above chance) classification accuracies (*p < 0.05; **p < 0.01; **p < 0.001). Black asterisks denote significant differences between conditions (*p < 0.05; **p < 0.01). Panel (b) represents, for each of these kinematic features, the mean kinematic profiles displayed by participants while performing PG actions on congruent and incongruent trials, during the noninteractive, the joint movement, and the joint outcome conditions. In each plot, the grey line represents the absolute difference between the mean kinematic profile displayed during congruent trials and the mean kinematic profile displayed during incongruent trials. For each kinematic feature, the kinematic difference between congruent and incongruent trials is visibly higher during the noninteractive condition, compared with the joint movement and the joint outcome condition

Fig. 4

Kinematic distance between confederate and participant. The graphs in the first column represent the mean kinematic profiles of Wrist Velocity (a), Wrist Acceleration (b), Grip Aperture (c), and Wrist Height (d), displayed by the confederate while performing PG or WHP actions during the noninteractive condition. The graphs in the second column represent, for each kinematic feature, the mean kinematic profile displayed by participants while performing PG actions during congruent trials (PG-PG motor sequence) or during incongruent trials (WHP-PG motor sequence) of the noninteractive condition. The graphs in the third column represent, for each kinematic feature, the mean kinematic profile displayed by the confederate while performing a WHP action (dotted line), and the mean kinematic profiles displayed by the participants in the first half (light grey) and second half (dark grey) of the trials of the noninteractive condition, while performing a PG action during incongruent trials (i.e. after observing the confederate perform a WHP action). The bar plots in the fourth column represent, for each kinematic feature, the Euclidean distance between the participants’ and the confederate’s kinematic profiles, during the first half and the second half of the incongruent trials of the noninteractive condition. Bars indicate standard error (SE). Asterisks denote significant differences (*p < 0.05; **p < 0.01)