This Is Your Brain on Music: The Science of a Human Obsession

by Daniel J. Levitin

To begin with, what might be the evolutionary basis for emotions? Scientists can’t even agree about what emotions are. We distinguish between emotions (temporary states that are usually the result of some external event, either present, remembered, or anticipated), moods (not-so-temporary, longer-lasting states that may or may not have an external cause), and traits (a proclivity or tendency to display certain states, such as “She is generally a happy person,” or “He never seems satisfied”). Some scientists use the word affect to refer to the valence (positive or negative) of our internal states, and reserve the word emotion to refer to particular states. Affect can thus take on only two values (or a third value if you count “no affective state”) and within each we have a range of emotions: Positive emotions would include happiness and satiety, negative would include fear and anger.