Though researchers have investigated the differences between volunteers and non-volunteers for psychological research, little is known about these differences when the research setting is a T-group. In the present study, volunteers and non-volunteers for T-groups were compared on authoritarianism, reported history of self-disclosure, and a series of questions on social relations. Volunteers, especially males, were lower in authoritarianism, whereas no differences were obtained for histories of self-disclosure. Also, female volunteers reported that they were less satisfied with their abilities to relate to others and that they spent less time with others. It was suggested that males may make a choice to volunteer by considering the compatibility of their social and political attitudes and those implied by T-groups. On the other hand, females may make their choice by considering their personal social relationships.
