This example is consistent with many recent studies that have also reported high levels of reciprocity in comparable situations (Allen-Arave et al. 2008; Gurven 2004; Gurven et al. 2000; Koster 2011; Nolin 2010; Wiessner 2005 136; Ziker 2007).
In the first experiment, social experience of the focal rats was manipulated by pairing them with cooperative or defective partners (stooges) that had either produced food for them ('cooperator') or not ('defector') in the identical but role-reversed situation (direct reciprocity [ 19]).
Here, we artificially created a situation of strong reciprocity (i.e. by employing susceptible cheats), but natural associations between pyocins and pyoverdine suggest that strong reciprocity may occur in natural populations of P. aeruginosa and perhaps bacteria in general.
A reciprocity arrangement introduced to improve the situation has become, Mr. Spacey said, "a bit of a star system," leaving out "a lot of people who don't qualify under the heading of international stars but are nonetheless brilliant, seasoned actors".
In situations characterized by diffuse reciprocity, there is an expectation that there will not be an equivalence of obligations or concessions in any one exchange, but, rather, a balance is expected over an ongoing, potentially indefinite, series of exchanges with a group of partners.
Thus, our study was aimed at investigating the effect on direct reciprocity between users on cooperation-dominant situations and how network structures affect the users' interaction strategy.
Costly signalling theory is a useful tool for understanding food sharing among hunter gatherers because it can be applied to situations in which delayed reciprocity is not a viable explanation.
As in trust, reciprocity is also expressed in different situations: in the examples above, the banker will work harder to maximize the earnings of the trustful investor, and a person that just stayed for free in someone else's house will more likely consider hosting as well [8].
Formal and informal rules were negotiated between the park administration and the community to ensure a win-win situation for both parties, demonstrating reciprocity.
7 This dynamical picture closely resembles the situation with the evolution of direct reciprocity.
