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. Author manuscript; available in PMC: 2008 May 27.
Published in final edited form as: Evolution. 2007 Aug 17;61(10):2281–2292. doi: 10.1111/j.1558-5646.2007.00196.x

Figure 2. Direct and indirect reciprocity can lead to the evolution of cooperation.

Figure 2

While direct reciprocity is based on repeated encounters between the same two individuals, indirect reciprocity uses the experience of others. Defectors are always ESS. Cooperators are ESS if w or q exceed (T − R)/(T − P), where w is the probability of another round in direct reciprocity, and q is the coefficient of social acquaintanceship under indirect reciprocity.