I assumed this would be a guide to understanding other people's emotional states based on the codes they were expressing (facial expressions, body posture, tone of voice, and so on). Non-verbal (unconscious?) communication seems to be an important feature of human emotional expression. People who never express any emotions at all tend to cause a certain degree of uneasiness in other people, although this is also characteristic of autism - and part of the treatment protocol for autism, I believe, is helping the subject learn how to express their emotional state to others, in a non-intrusive and situationally-appropriate manner.<p>Geek/nerd-wise, the first thing that comes to mind is, what is an emotion? How does it differ from an animal instinct, or from a conscious thought expressed as a symbolic string? Consider, for example, the rather unpleasant emotionally manipulative human type, who first thinks "What emotion should I express now to get what I want" and then deliberately engages in that emotion to trigger a desired response in others. (Young children often have to be gently advised that this is not going to work, some are not taught this and so persist in this behavior as adults). Where does instinct become emotion become thought?<p>Another interesting human behavioral type is the emotional button-pusher, who tries to elicit strong emotions in others, for their own usually unpleasant purposes. The best defense against this dark art is probably meditation, which in part involves learning how to recognize an emotional state at the moment it arises, before one takes any action on it.<p>At the very least, a wise human recognizes that actions are best taken with at least a modicum of rational input, and should never be wholly emotional in nature. And sometimes, having a little cooling off period is the best option of all (particularly with strong emotions). On the other hand, the saying "trust your instincts" should not be disregarded.