1996 年 67 巻 2 号 p. 77-85
Two experiments examined the effect of illusion of control on ingroup favoritism found in the minimal group situation (Tajfel, Billig, Bundy, & Flament, 1971). In bilateral dependency condition, each member made allocation decisions for ingroup as well as outgroup participants. It was exactly the same situation used in the original studies under the minimal group paradigm, and the subjects knew that their reward allocation too depended on others' decisions. In contrast, in unilateral dependency condition, the subjects made allocation decisions knowing that theirs were not dependent on others' decisions. In Experiment 1, an ingroup bias in reward distribution was found in the bilateral dependency condition, but not in the unilateral condition. In Experiment 2, it was found that only those who felt illusion of control exhibited such an ingroup bias. Results of the experiments therefore confirmed that illusion of control explained ingroup favoritism, as Karp, Jin, Yamagishi, and Shinotsuka (1993) originally hypothesized.