Response predictability in joint action


In a recent study, Campos-Moinier and Brunel (2021) modified the joint Simon task to demonstrate that shared online information was not essential to represent actions in a joint task. The participant and co-actor sat side-by-side, each with their own display, and a barrier restricting visual input to their own display. The stimulus was presented on one of the two displays. Participants had to respond as quickly as possible to their assigned stimulus, even when it appeared on their partner's unseen display. Campos-Moinier and Brunel showed that: 1) a joint Simon effect (JSE) could be obtained even when actors did not share online information, and 2) the magnitude of the JSE was correlated with the variability of the co-actor's reaction times (RT) on compatible trials. The authors reasoned that in the absence of shared information, participants relied upon external feedback of the co-actor's responses (hearing them respond) to code their actions and resolve self-other discrimination, as well as used the predictability of their co-actor's responses to make decisions about their own responses. We propose that Campos-Moinier and Brunel's task modifications substantially changed the nature of the joint Simon task. Incompatible responses would always be longer than compatible responses because participants must wait for the co-actor's response-produced auditory feedback. Indeed, their reported "JSE" is not even contingent on performing the task with another person. In the present study, we show that Campos-Moinier and Brunel's joint action effect can be replicated when participants complete the same task with a computer as the "co-actor".

Acknowledgments: Supported by Natural Sciences and Engineering Research Council of Canada