© The IO Foundation 2014. Why do some decision makers prefer big multilateral agreements while others prefer cooperation in small clubs? Does enforcement encourage or deter institutional cooperation? We use experiments drawn from behavioral economics and cognitive psychology - along with a substantive survey focused on international trade - to illustrate how two behavioral traits (patience and strategic reasoning) of individuals who play key roles in negotiating and ratifying an international treaty shape their preferences for how treaties are designed and whether they are ratified. Patient subjects were more likely to prefer treaties with larger numbers of countries (and larger long-term benefits), as were subjects with the skill to anticipate how others will respond over multiple iterations of strategic games. The presence of an enforcement mechanism increased subjects' willingness to ratify treaties; however, strategic reasoning had double the effect of adding enforcement to a trade agreement: more strategic subjects were particularly likely to favor ratifying the agreement. We report these results for a sample of 509 university students and also show how similar patterns are revealed in a unique sample of ninety-two actual US policy elites. Under some conditions certain types of university student convenience samples can be useful for revealing elite-dominated policy preferences - different types of people in the same situation may prefer to approach decision-making tasks and reason through trade-offs in materially different ways.