I argue that altruistic behavior and its variation across cultures may be caused by mental cognitive mechanisms that induce cooperative behavior in contract-like situations and adapt that behavior to the kinds of contracts that exist in one's socio-cultural environment. I thus present a cognitive alternative to Henrich et al.'s motivation-based account. Rather than behaving in ways that reveal preferences, subjects interpret the experiment in ways that cue their social heuristics. In order to distinguish the respective roles of preferences and cognitive processes that determine economic behavior, we need more ethnography of strategies “in the wild.”