The sociality of social inhibition of return

Cognitive processes are traditionally studied in individual settings, while the possible effect of the social context is ignored. The present study focuses on the social inhibition of return effect (SIOR; Welsh et al., 2005). According to it, observation of another person's action at a specific location initiates an inhibitory process in the observer at that location. The aim of the present study was to investigate which processes are influenced by the social context (e.g. action representation, attention, etc.) and whether this effect is elicited only in a social context. In a series of four experiments we examined the SIOR effect by developing a dyadic computerized task in which each participant, in turn, responded to a peripherally presented target in two successive trials. The first trial was performed after the other participant had responded and was designed to examine SIOR. The second trial was aimed at studying self-induced IOR. The first two experiments replicated and extended previous findings by demonstrating that information regarding the counterpart's response location was sufficient to produce SIOR. In the third experiment the participants performed the same task but without a counterpart so that SIOR was eliminated. The fourth experiment demonstrated that believing there is a co-actor is enough to elicit the SIOR effect. These findings suggest that knowing that a location was acted upon before by another person (by observation or by prior knowledge) is the minimal condition for the SIOR effect to be evoked.