Does an altruist-detection cognitive mechanism function independently of a cheater-detection cognitive mechanism? Studies using Wason selection tasks Ryo Oda a, 4 , Kai Hiraishi b , Akiko Matsumoto-Oda c a Graduate School of Engineering, Nagoya Institute of Technology, Nagoya 466-8555, Japan b Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan c Department of Welfare and Culture, Okinawa University, Naha 902-8521, Japan Initial receipt 16 July 2005; final revision received 27 March 2006 Abstract Subjects performed four deontic Wason selection tasks in three experiments to investigate possible commonalities in people’s performance in making logical inferences in social contexts. These tasks tested sensitivity to another party being an altruist, cheater or willing to share a resource and following a precaution rule in the context of danger. The results indicated no significant association between performance on the altruist detection and the cheater detection tasks. This result suggests that whatever the nature of the altruist-detection algorithm, it functions independently of the cheater- detection algorithm. The results also indicated significant associations between the cheater-detection task and the resource-sharing task. Possible mechanisms and functions of social intelligence suggested by these results are discussed. D 2006 Elsevier Inc. All rights reserved. Keywords: Altruist detection; Cheater detection; Darwinian algorithm; Deontic reasoning; Wason selection task 1090-5138/06/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.evolhumbehav.2006.03.002 4 Corresponding author. Tel.: +81 52 735 5112; fax: +81 52 735 5112. E-mail address: oda.ryo@nitech.ac.jp (R. Oda). Evolution and Human Behavior 27 (2006) 366 – 380