 On the heels of work on the effects of time (finite iteration versus infinite iteration) and memory/cognitive ability (finite state automata versus Turing machines), attention soon turned to environmental constraints. Nowak and May looked at the spatial distribution on a two-dimensional grid of ‘cooperators’ and ‘defectors’ in iterated prisoner’s dilemmas and found cooperation to emerge among players without memories or strategic foresight (Nowak &amp; May 1992). This work led to the study of network topology as a factor in social behavior (Jackson 2010), including social norms (Bicchieri 2005; J. Alexander 2007), signaling (Skyrms 2003), and wisdom of crowd effects (Golub &amp; Jackson 2010). When social ties in a network follow a scale-free distribution, the resulting diversity in the number and size of public-goods games is found to promote cooperation, which contributes to explaining the emergence of cooperation in communities without mechanisms for reputation and punishment (F. Santos, M. Santos, &amp; Pacheco 2008).