When things aren't going well, sometimes you just have to Walk Away.  This is the essence of conditional movement.  A careful consideration of conditional movement strategies such as Walk Away can help us  understand the emergence of cooperation from simple individual-level rules.  I introduced the 'Walk Away' strategy in my 2004 Journal of Theoretical Biology paper "Know When to Walk Away" [download].  You can see my talk on the Walk Away strategy and the the evolution of cooperation at UCLA's Center for Behavior, Evolution and Culture on the web or download it from iTunes U.

What is Walk Away?

Walk Away is cognitively simple, evolutionarily ancient, phylogentically widespread, and generates aggregate dynamics that promote the evolution of cooperation.  It is based on the notion that individuals can leave regions, partners or groups that are insufficiently productive, which can be done by simply co-opting foraging adaptations [download manuscript].  Walk Away is a conditional movement strategy. 

How does Walk Away work?

When individuals use such a Walk Away strategy, this generates differential stability of cooperative partnerships and groups,  increasing the likelihood that cooperators will interact with one another (relative to defectors).   This leads to selection for cooperation in the overall population despite the within-group advantage of defectors.

What are the Implications of Walk Away?

The Walk Away model has several key implications.  First, it demonstrates that complex cognitive abilities are not necessary for the evolution of cooperation [download manuscript] and that Walk Away can outperform other simple strategies such as Tit-for-Tat and PAVLOV [download Aktipis 2004, JTB].  Second, it demonstrates that conditional movement can favor the evolution of cooperation via group selection even when individuals are highly mobile.  This challenges the conclusions of standard group selection models which assume random movement [download manuscript].  Third, Walk Away provides a mechanism by which cooperation can emerge regardless of genetic structure, suggesting that it might play a role in the emergence of complexity at various stages in the evolution of life including the development of multicellularity, symbiosis, parental investment and sociality (project in progress with Aurora Nedulcu).