| Summary: | The aim of this dissertation was twofold: (1) to examine task co-representation and joint action in efforts to identify necessary preconditions under which shared representations are formed and (2) to determine whether alternative explanations can account for the social Simon effect (SE). Using joint Simon effect protocols (e.g., Sebanz & Knoblich 2003), we began (Study 1) by showing that when paired participants responded to the same stimulus-response alternative, the joint SE was absent. When participants performed under a competitive context (Study 2), the joint SE was elicited, even though co-representation would have been disadvantageous with respect to the task goal. Next, we examined the influence of spatial and response discrimination factors on the joint action correspondence effect. Our first investigation (Study 3) did not support the assumption that the co-actor may be providing a reference for the spatial coding of alternative responses. Using Ansorge and Wühr’s (2004) response discrimination hypothesis as a framework, we showed in subsequent studies (Study 4 & 6) that a SE could be elicited in a Go/No-Go task when spatial codes were used to discriminate between alternative responses. This was demonstrated when a standard 2-choice task preceded a Go/No-Go task and when participants performed two independent tasks alongside each other. Examination of event-related potentials pertaining to action inhibition suggested reduced action suppression on no-go trials when performing with a co-actor compared to performing with alone under these independent task conditions. In a final study (Study 7), we explored task co-representation using a different experimental paradigm—the response-precuing task. Our results did not provide clear evidence for task co-representation. In cases where the ‘social’ SE was not observed, we propose that a form of ‘social loafing’ or an individualistic mindset approach to the joint action task may have been in operation. Our overall findings encourage further investigation of how task context can modulate the joint SE and highlights how an individualistic mindset can potentially preclude co-representation.
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