Publications of van der Wel, R.P.

Making oneself predictable: Reduced temporal variability facilitates joint action coordination

Performing joint actions often requires precise temporal coordination of individual actions. The present study investigated how people coordinate their actions at discrete points in time when continuous or rhythmic information about others' actions is not available. In particular, we tested the hypothesis that making oneself predictable is used as a coordination strategy. Pairs of participants were instructed to coordinate key presses in a two-choice reaction time task, either responding in synchrony (Experiments 1 and 2) or in close temporal succession (Experiment 3). Across all experiments, we found that coactors reduced the variability of their actions in the joint context compared with the same task performed individually. Correlation analyses indicated that the less variable the actions were, the better was interpersonal coordination. The relation between reduced variability and improved coordination performance was not observed when pairs of participants performed independent tasks next to each other without intending to coordinate. These findings support the claim that reducing variability is used as a coordination strategy to achieve predictability. Identifying coordination strategies contributes to the understanding of the mechanisms involved in real-time coordination.

Let the force be with us: Dyads exploit haptic coupling for coordination

People often perform actions that involve a direct physical coupling with another person, such as when moving furniture together. Here, we examined how people successfully coordinate such actions with others. We tested the hypothesis that dyads amplify their forces to create haptic information to coordinate. Participants moved a pole (resembling a pendulum) back and forth between two targets at different amplitudes and frequencies. They did so by pulling on cords attached to the base of the pole, one on each side. In the individual condition, one participant performed this task bimanually, and in the joint condition two participants each controlled one cord. We measured the moment-to-moment pulling forces on each cord and the pole kinematics to determine how well individuals and dyads performed. Results indicated that dyads produced much more overlapping forces than individuals, especially for tasks with higher coordination requirements. Thus, the results suggest that dyads amplify their forces to generate a haptic information channel. This likely reflects a general coordination principle in haptic joint action, where force amplification allows dyads to perform at the same level as individuals.