Abstract
In daily life we often encounter situations in which we have to coordinate our actions with others to perform a task. Such joint action is considered to be fundamental to social interactions. In this study we set out to explore how interpersonal movement coordination in a joint action task is guided by the use of visual information from the task environment. To this end we designed an (interpersonal) ball-and-beam task in which agents control the motion of a golf ball on a two-meter long beam by (jointly) changing the inclination of the beam through manipulation of the height of (one of) the hand-held extremities. In the experiment 24 healthy participants (15 men, 9 women, age 19-34) were to roll the ball as often as possible between two targets on the beam (distance 140 cm, width 15 cm), with a point awarded for each ball motion direction reversal occurring within a target. The experiment consisted of a solo and a duo session, each containing 15 two-minute trials, in which participants performed the ball-and-beam task either alone or in cooperation with another participant. Ball and beam motions were tracked using passive reflective markers and Kinovea motion capture software. In both sessions, we found that the overall performance on the task improved over practice, accompanied by an increase in beam amplitude and a decrease in ball cycle time. Perception-action coupling was first explored in the solo sessions, allowing two different types of behavioral dynamics to be identified. We tentatively conclude that these different dynamical patterns emerge from differences in the visual information used at the level of the ball trajectory. The next step in the project is to explore the role of visual information in guiding interpersonal coordination in the duo (i.e., joint action) version of this simple yet rich experimental paradigm.