Commitment and evolution: connecting emotion and reason in long-term relationships

Long-term interpersonal relationships are everywhere. People instinctively establish contact with strangers, invest in getting to know each other, and often go to great lengths to avoid losing existing relationships. Many relationships yield obvious benefits for involved parties, monetary or otherwise, and it is only rational to establish and maintain them. Yet, it sometimes seems difficult to find rational explanations for the existence or continuation of certain relationships in which people ignore their own instrumental interest and practical advantages. The apparent explanation for such seemingly irrational behavior is that, with regard to relationships, people are especially prone to act under the influence of emotions. It has been argued, in fact, that many of the strongest emotions people experience in life, both positive and negative, are somehow linked to relationships. This work attempts to answer why such emotions came to diverge from rationality in the first place. Building on previous work, we use evolutionary theory and computer simulations to provide mathematical models of relationship-building, and to thereby compare different strategies with regard to commitment to long-term partners. Subsequently, we test some of the implications of these models using human subjects in controlled cross-cultural experiments.