Making sense of emotion: evolution, reason & the brain.

We often define the basic goals of human striving in terms of emotion: we yearn for happiness and do our utmost to avoid misery. (1) But making the distinction between positive and negative emotions is not as simple as saying that we seek the former and shun the latter. Emotions often have a will of their own and may resist attempts to be disciplined. Victims of wartime atrocities and natural disasters, for example, may unwillingly suffer from involuntary flashbacks in which they re-experience the trauma, eliciting intense fright that threatens or undermines adjustment. But some individuals--such as journalists, photographers, and Peace Corps workers--are willfully drawn to those very fear-ridden circumstances, not to mention people who find their (sometimes compulsive) joy in activities most of us fear--parachute jumping, mountain climbing, or extreme skiing. Likewise, our lives may become devastated by the prototypical emotion we all desire, passionate love, and we may ruin our health with the delights of food and drink. Still, for most of us, life without emotion would not be worth living. But at the same time, others have regarded emotion as a dark, alien force to which we helplessly succumb, to our own detriment.

Clearly, emotions resist simple interpretation. The purpose of this essay is to discuss the conflicting nature of emotion in light of modern research in psychology and neuroscience. I start with some philosophical considerations that lead to a conceptualization of emotion that ties emotion to the body via evolutionary biology and neuroscience. I then review how contemporary science has addressed some of the classic questions of emotion research.

The conflict-ridden nature of emotion has been evident throughout recorded intellectual history. Almost 2,500 years ago, at the birth of Greek philosophy, Demokritos said that we need wisdom to cure the mind of emotion the way we need medicine to cure bodily ailments. (2) This idea was central to the Epicurean and Stoic philosophical movements, which predicated their notions of the good life on the insight that we are disturbed not by things themselves but by what we make of them. Reason tells us that we need not fear death because we shall not be there to experience it. We should enjoy food, drink, and intellectual exchange in the context of cultivating friendship. But we should not let emotions associated with insatiable desires for ephemeral things--such as wealth, fame, and power--seduce us. In contrast, the early Christians did not trust the power of reason to control emotion, but made a handful of problematic emotions central to the deadly sins (the committing of which did make death something to fear): avarice, lust, envy, gluttony, indifference, pride, and wrath.

The Stoics made an interesting distinction--between the first and second 'movements' of an emotion. The first movement is reflexive, such as when we instinctively duck for a swooping bird or stop dead when confronted by a snake. The second movement is what we make of this instinctive response: How dangerous is the situation? Will the bird attack again? Is the snake poisonous? This process of evaluation depends on voluntary mental activity. For example, after the initial surge of erotic excitement upon encountering an overwhelmingly attractive potential partner, one might then rationally analyze the situation, which may result in emotional deactivation by shifting one's attention to something less evocative. By making the second movement the essence of emotion, the Stoics changed the meaning of emotion from an automatic and involuntary response to something individuals could consciously control and take responsibility for.

The enigmatic nature of emotion may be one reason science has long neglected it. But there are other reasons as well. The way we normally know emotions is through feelings, which are elusive, capricious, and probably changed by the very act of observing them. Above all, they are observable only in the mind's eye of the emoter. Feelings, therefore, elude science, which aspires for an objective database in which observers can agree on raw data accessible to many observers. Accordingly, some have argued that the subjective nature of feelings excludes them from the realm of science.