The relationship between game play and naturalistic cooperation, generosity, or market involvement is ambiguous at best, making it difficult to link game results to preferences and beliefs guiding decision-making in daily life. Discounting reputation-based explanations because the games are anonymous, while arguing that game play is guided by motivational structures or framing effects reflecting daily life, is inconsistent.

Selfishness narrowly defined as choosing dominant outcomes independent of context is widely rejected by experimentalists. Humans live in two worlds of personal and impersonal exchange; both are manifestations of human sociality, but the emphasis on preferences rather than cultural norms of personal exchange across time too much reflects a limited economic modeling, and fails to capitalize on the fresher experimental economics message of culture and diversity.

Henrich et al.'s findings are generally consistent with the findings of other experimental field studies. However, the methodological variations deployed across field sites produced several systematic biases in their results. Hence, although the project is destined to become a watershed study, their results should be interpreted prudently.

Henrich et al. reject the “selfishness axiom” within a narrowly-defined economic model, and are premature in claiming that they have demonstrated cross-cultural variability in “selfishness” as defined in broader evolutionary theory. We also question whether a key experimental condition, anonymity, can be maintained in the small, cohesive, social groupings employed in the study.

Alternative interpretations are proposed for the finding that market integration is positively related to fair behavior in experimental games. Market activities may produce market relevant concepts and stories that interpret experimental games as incidences of social exchange, and thus may enhance the relevance of (1) market-related preferences or (2) a decision heuristic designed for social exchange.

“Economic man” assumes not only self-interest, but also rationality of choices. The finding that ultimatum game offers can be explained by ambiguity aversion as well as pessimism, plus other findings, suggests the usefulness of taking bounded rationality more into account. Neurodevelopmental and heritability research supports the authors' emphasis on the importance of social learning and socialization.

We would like to thank the commentators for their generous comments, valuable insights and helpful suggestions. We begin this response by discussing the selfishness axiom and the importance of the preferences, beliefs, and constraints framework as a way of modeling some of the proximate influences on human behavior. Next, we broaden the discussion to ultimate-level (that is evolutionary) explanations, where we review and clarify gene-culture coevolutionary theory, and then tackle the possibility that evolutionary approaches that exclude culture might be sufficient to explain the data. Finally, we consider various methodological and epistemological concerns expressed by our commentators.

Matthew Walker's model overcomes the unrefined classical concept of consolidation as a unitary process. Presently still confined in its scope to selective data mainly referring to procedural motor learning, the model nonetheless provides a valuable starting point for further refinements, which would be required for a more comprehensive account of different types and aspects of human memory consolidation.