Kameda,T.
Takezawa,M.
Tindale,R.S.
Smith,C.M.

Sharing important resources widely beyond direct kin group members is one of the core features characterizing human societies. Moreover, generalized exchange involving many community members (e.g., meat sharing in bands) seems to be a uniquely human practice. This paper explores a computational algorithm for the psychology of social sharing that may underlie such practices, based on the risk-reduction hypothesis in food sharing of Kaplan and Hill [Curr. Anthropol. 26 (1985) 223]. We predicted that, independent of the amount of effort actually invested, uncertainty involved in resource acquisition is a key factor that triggers the psychology of social sharing for both acquirers and nonacquirers of a resource. It was also predicted that the "windfall effect" is independent of individual preferences as to modern distributive ideologies. Four multisample/multimethod studies, using Japanese and American participants, and laboratory as well as vignette experiments, supported these predictions: although the identical fungible resource (money) was under consideration, different psychological processes were triggered, depending on the degree of uncertainty involved in the money acquisition. Implications of the windfall effect for egalitarianism in resource sharing, observed not only in personal advantage. In other words, it seems that an acquirer of a resource under uncertainty shows some egalitarian tendency behaviorally, but not always "willingly." One interesting study illustrates this point. Eckblad and von der Lippe (1995) investigated 261 lottery winners of prizes of 1 million Norwegian krone (=US$150,000). Those winners were asked about various psychological reactions after winning the prizes. One of the most frequent reactions among those respondents was a wish for anonymity, together with fear of envy from others! These observations seem to suggest that social sharing under uncertainty essentially may be characterized as a "vigilant sharing" (Erdal & Whiten, 1994), in which sharing is conducted because of vigilant and envious eyes of nonacquirers who are immediate beneficiaries of sharing. In other words, nonacquirers may play a more active, initiative role in social sharing, implicitly or explicitly, than the acquirer of the resource (cf. Bliege Bird & Bird, 1997; Blurton Jones, 1987; Hawkes et al., 2001; Peterson, 1993). Notice that this view is not contradictory to the risk-reduction perspective, since those who face the immediate risk of resource shortage are nonacquirers and not the acquirer of the resource. (See Kameda et al., submitted, for an evolutionary game model of resource sharing under uncertainty based on these "demand sharing" notions.) In any event, this reasoning suggests that there may be some asymmetry between acquirers and nonacquirers, with the psychology of windfalls being more easily and/or more vigorously activated among nonacquirers. Given that the modern notion of property rights should operate in exactly the opposite way (i.e., sharing is at the acquirer's discretion), this poses an intriguing possibility awaiting future investigations. As often pointed out by various theorists, human resource sharing, including food sharing, is a complex phenomenon, and its adaptive origins are most likely manifold. Given this complexity, a multidisciplinary approach seems to be essential to better understand the phenomenon. We followed such a path in this paper, by linking social psychological experimentation to anthropological findings to shed some light on the psychology of social sharing. Much remains to be done, but we believe that a multidisciplinary approach under the evolutionary perspective will eventually clarify the computational algorithm underlying social sharing in a rigorous manner.

Kameda, T., Takezawa, M., Tindale, R. S., & Smith, C. M. (2002). Social sharing and risk reduction: Exploring a computational algorithm for the psychology of windfall gains. Evolution and Human Behavior, 23, 11-33. (Full text)

Publication year	2002
Document type:	Article
Publication status:	Published
External URL:	http://dx.doi.org/10.1016/S1090-5138(01)00086-1 View
Categories:	ForecastingEducation
Keywords: