Although the hand is an important organ in interpersonal interactions, focusing on this body part explicitly is less common in daily life compared with the face. We investigated (i) whether a person's recognition of their own hand is different from their recognition of another person's hand (i.e., self hand vs. other's hand) and (ii) whether a close social relationship affects hand recognition (i.e., a partner's hand vs. an unknown person's hand). For this aim, we ran an experiment in which participants took part in one of two discrimination tasks: (i) a self-others discrimination task or (ii) a partner/unknown opposite-sex person discrimination task. In these tasks, participants were presented with a hand image and asked to select one of two responses, self (partner) or other (unknown persons), as quickly and accurately as possible. We manipulated hand ownership (self (partner)/other(unknown person)), hand image laterality (right/left), and visual perspective of hand image (upright/upside-down). A main effect of hand ownership in both tasks (i.e., self vs. other and partner vs. unknown person) was found, indicating longer reaction times for self and partner images. The results suggest that close social relationships modulate hand recognition-namely, "self-expansion" to a romantic partner could occur at explicit visual hand recognition.
Keywords: hand recognition; self-other discrimination; social relationship.