While concurring that the evidence from individual differences supports a Meliorist view in the rationality debate, this commentary suggests that (1) the evidence does not clearly support a two-systems interpretation against an interpretation in terms of idiosyncratic differences in mental models, and that (2), especially where interactional processing is concerned, evidence from experimental game theory should also be considered.

This commentary suggests that an equilibrium framework may be retained, in an evolutionary model such as Gintis's and with more satisfactory results, if rationality is relaxed in a slightly different way than he proposes: that is, if decisions are assumed to be related to rewards probabilistically, rather than with certainty. This relaxed concept of rationality gives rise to probabilistic equilibria. (Published Online April 27 2007).