Abstract
Most of our actions are influenced by the social context, in particular, by the presence of others and the actions performed by others. Previous studies have shown that observing others' actions can affect individual performance of the same actions. In order to investigate the effects of the presence of others on an individual's performance of the Simon task, we conducted three experiments in three conditions: individual (only individual presented), joint (two persons performed simultaneously), and nojoint condition (two persons present while only one performed). We developed a new Simon task paradigm, in which each person only responded to on trials designated by special fixation point style. In Experiment 1, two persons performed a Simon task sitting side by side. Simon effect was observed in every condition when the same person made a response in two consecutive trials (‘go’ trial), whereas Simon effect was observed after another person made a response (‘no-go’ trial) only in the joint condition. In Experiment 2, we examined whether Simon effect was observed when a person performed with another person whose color-key assignment was reversed. The result showed no Simon effect in the joint no-go condition. In Experiment 3, two persons with the same color-key assignment performed the task sitting face to face or side by side. In face to face condition, there was no Simon effect in joint no-go condition. These results showed that after go trial Simon effect always occurs and that after no-go trial Simon effect occurs in only the joint condition in which two persons with the same color-key assignment performed the Simon task sitting side by side. This suggests that one's own actions and others' actions are represented in a functionally equivalent way in particular situations. We will discuss a possibility that other's existence, perception of other's action, and the sight of others affect our action in terms of sequential analyses of S-R compatibility in the preceding trial.
Support from 21st Century COE (D-2 to Kyoto Univ.), and PRESTO from JST.