A recent issue of Science has a couple of interesting articles on Cooperation and altruism. There are two types of agents Cooperators (C) and Defectors (D). Groups of only cooperators have a higher average fitness than groups of defectors, but defectors have a higher individual fitness than cooperators (Nowak 2006). Defectors will inevitably take over any group of cooperators if there are not any mechanisms to work against it. So, for cooperation to have evolve, mechanisms to prevent invasion by defectors must be in place. Such a battery of defense mechanisms against defectors may be seen ostrachism and punishment of rule violators and costly displays of allegience (Costly Signaling). But the article by Nowak indicates another possible mechanism.
One thing I found particularly interesting was a simple rule that describes under what conditions altruistic cooperation can take place in a situation of indirect reciprocity. Indirect reciprocity takes place in situations where there is no possibility for direct reciprocity, either because the persons will never meet again or becaue one is in a subordinate position and cannot reciprocate. In these cases altruistic helping behavior is explained by the fact that ”helping someone establishes a good reputation, which will be rewarded by others” (1561). A good reputation, therefore, increases the possibility that others will help you. Nowak concludes: ”Indirect reciprocity can only promote cooperation if the probablity, q, of knowing someone’s reputation exceeds the cost-to-benefit ratio of the altruistic act: q>c/b”(1561)
This is an interesting observation because the probaility of knowing someone’s reputation is dependent on factors such as population size, proximity of the action to home and dissemination of information about reputation. It is interesting to notice that gossip seems to be exactly this, information about reputation. Gossip therefore increases q which increases the sustainable cost-to-benefit ratio in the group. If the probability of knowing someones reputation is higher it is possible to establish cooperation with higher costs to lower benefits. Thus – gossiping populations favor altruistic acts. Gossip is therefore also a mechanism in fighting invasion by defectors.
Supporting online material containing the relevant equations: http://www.sciencemag.org/cgi/data/314/5805/1560/DC1/1
Nowak, M. A. (2006). "Five Rules for th eEvolution of Cooperation." Science 314(8 December): 1560-1563.
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2 comments:
What exactly is gossip? I mean is there an analytical definition that distinguishes it from other types of communication?
David Sloan Wilson and Kevin Kniffin define gossip thus: "we define gossip to include positive and negative talk about commonly associated people" (http://biology.binghamton.edu/dwilson/Wilson%20publications/DSW08.pdf). I think this definition as sufficiently precise and aims exactly at the reputation of people.
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