Decisions, Thoughts, and Feelings
It is tempting to construct a model of the ideal human being, the modern descendant of Plato's philosopher-king. Such a person would be thoughtful, perceptive, and rational, just like Homo economicus— yet also presumably highly moral and ethical. Decisions would be made and actions chosen based on a careful and sensitive analysis of the circumstances.
The capacity to think like a philosopher-king is, however, quite a recent development in evolution. Outside humankind, rational and moral thinking is very limited or indeed wholly absent in most cases. Yet animals have been making choices since very early in evolution. How did they make them, if they were unable to conduct logical cost-benefit analyses of competing prospective scenarios?
Choosing on the basis of how one feels right now is a simpler process than making rational decisions, and it requires less mental hardware. We suspect that the earliest feelings to emerge in evolution included pain, which functioned as a signal to the organism that it should move in order to escape from being injured and damaged.