How “social” is the social Simon effect?

Thomas Dolk,Lorenza S Colzato,Roman Liepelt,Simone Schütz-Bosbach,Bernhard Hommel,Wolfgang Prinz

doi:10.3389/fpsyg.2011.00084

Abstract

In the standard Simon task, participants carry out spatially defined responses to non-spatial stimulus attributes. Responses are typically faster when stimulus location and response location correspond. This effect disappears when a participant responds to only one of the two stimuli and reappears when another person carries out the other response. This social Simon effect (SSE) has been considered as providing an index for action co-representation. Here, we investigated whether joint-action effects in a social Simon task involve mechanisms of action co-representation, as measured by the amount of incorporation of another person's action. We combined an auditory social Simon task with a manipulation of the sense of ownership of another person's hand (rubber hand illusion). If the SSE is established by action co-representation, then the incorporation of the other person's hand into one's own body representation should increase the SSE (synchronous > asynchronous stroking). However, we found the SSE to be smaller in the synchronous as compared to the asynchronous stroking condition (Experiment 1), suggesting that the SSE reflects the separation of spatial action events rather than the integration of the other person's action. This effect is independent of the active involvement (Experiment 2) and the presence of another person (Experiment 3). These findings suggest that the “social” Simon effect is not really social in nature but is established when an interaction partner produces events that serve as a spatial reference for one's own actions.

Highlights

Many activities we perform in daily life are carried out together with other people
We were able to replicate the findings of Sebanz et al (2003), confirming that our particular setup was sufficiently sensitive to elicit the social Simon effect” (SSE) in both the synchronous and the asynchronous stroking conditions
We found the effect to be smaller, rather than larger, with synchronous than with asynchronous stroking. The incorporation of another person’s hand into one’s own body schema through the rubber hand illusion (RHI) reduces the SSE as compared to a condition where the co-actor is represented as a separate actor. This interpretation is supported by the subjective rating of the sense of ownership of the co-actor’s hand in the synchronous stroking condition, which indicates that the experimental RHI manipulation was successful across all phases of the experiment

Summary

Introduction

Recent research suggests that joint action can lead to the representation of one’s own and other’s actions This “action co-representation” is thought to facilitate action prediction and coordination of one’s own actions with those of others (Sebanz et al, 2006). Spatial stimulus–response compatibility facilitates task performance, a phenomenon that has come to be known as the Simon effect. This effect disappears when a participant responds to only one of the two stimuli, rendering the task a “go–nogo task” (Hommel, 1996). If the same go–nogo task is shared between two participants so that each of them operates one of the two responses, a Simon effect is observed (Sebanz et al, 2003) – the “social Simon effect” (SSE)

Methods

Results

Conclusion