**Faculty Candidate at MIT Sloan School of Management**

What makes people willing to pay costs to benefit others? I will explore this question from a cognitive perspective, using a combination of formal evolutionary game theoretic models and behavioral experiments. In particular, I focus on the trade-off between ease and flexibility in decision-making. I will present models that suggest that processes that are relatively cheap (in terms of time and effort) but inflexible should tend to favor cooperation, as cooperation is typically long-run payoff-maximizing (due to forces such as repeated interactions, reputation concerns, and institutions). Exerting more effort to adapt flexibly to the details of the situation, however, leads to defection in atypical situations where cooperation does not actually pay off in the long run (e.g. 1-shot anonymous interaction). Thus, cooperation in such 1-shot settings can be explained as part of an optimal strategy, functioning as a cost-saving heuristic for social interaction. I will then present empirical data from laboratory experiments validating the predictions of this modeling framework: increasing the cost of deliberation (e.g. by applying time pressure or cognitive load) increases cooperation in 1-shot economic cooperation games (where cooperation is costly) but has no effect in strategic games where cooperation can be payoff-maximizing (and thus the inflexible heuristic is appropriate).