The present book adds to the broad field of investigations concerning what affects and determines human cooperation. It provides new insights into internal and external factors that influence such decisions. Rather than presenting a closed and universal examination, this book should be seen as...

Altruists and envious people who meet in contests are symbionts. They do better than a population of narrowly rational individuals. If there are only altruists and envious individuals, a particular mixture of altruists and envious individuals is evolutionarily stable.