On the nature of emotion.

This essay has tried to make three points. First, humans are capable of a large number of affect states (the exact number is not yet known), each marked by a distinct profile of physiology, cognition, and behavior, and each requiring a distinct name. Second, a distinction should be made among acute emotions, chronic moods, and temperamental vulnerabilities to a particular emotion state. Finally, research on human affects will profit from a return to, and a reinterpretation of, Freud's suggestion of unconscious affect states. Such inquiry would provide a corrective to the current reliance on the verbal reports of phenomenal states on questionnaires or in interviews as either the only, or the primary, index of an emotion. Continued use of this strategy will limit analyses to a small number of heterogeneous states that happen to have a popular English name and will retard discovery of the larger number of affect states that are of significance for human function. Discovery of these states will require use of new sources of evidence to supplement popular ones, including facial and postural expressions, muscle tension, EEG, vagal tone, heart-rate changes, blood pressure, GSR, facial temperature, and blood or saliva indexes of norepinephrine, opioids, and cortisol. When the cosmologist James Peebles was asked to guess the exact numerical answers to a series of astronomical puzzles, like the age of the universe or of a distant star, he replied, "If someone gave me on a tablet of clay the answer and the numbers, I would be disappointed. I would throw it away because the great discoveries are not going to be a final number, but the method you come to apply to learn that number."