when we turn to excess work similarly whether the target is food, drugs, alcohol, gambling, or, I suggest, violence. It is a malfunction that reveals what happens when you unhinge desire from the experience of reward.
The work on addictive behavior tells us that independently of how people get started on the path to fulfilling their desires, and whatever leads them to over-consume, consumption loses its luster. The brain is smart: excess is bad and so the reward system shuts off. This creates a major problem because the wanting system is still turned on, looking for pleasure in all the wrong places. The result: unfulfilled cravings.
The work on addiction provides a template for thinking about how individuals step onto a path that leads to excessive harms. In the same way that excessive eating gets going and going out of control when the dopamine system drives an irrational desire to want more and more food that is liked less and less, so too I suggest can excessive harm arise when wanting and liking part company. Individuals start with a desire to acquire wealth, to physically harm those who are unlike them, or taste the sweetness of revenge against someone who acted unfairly. These desires are often linked to a rewarding experience or the anticipation of one, a point I will soon support with evidence. But as such actions and their consequences accumulate, the pleasure derived diminishes. Liking is no longer part of the equation; but wanting is. The result: unsatisfied cravings blind individuals to the harms caused.
To develop the analogy between food, drug, alcohol and gambling addictions on the one hand, and addictions to violence on the other, I need to fill in several missing pieces, starting first with a richer description of the psychology of desire. Everything I have discussed in this section has focused on individuals and their core corporal needs for survival — or in the case of drugs and gambling, recreation. I haven’t said a word about how desire works in the social arena, whether the same systems are in play when we compare our own desires and resources with others, or with other opportunities. When desire is motivated by what others have or have achieved, are the same processes in play as when we eat, drink, or gamble? These are important questions as the desire to accumulate great wealth or to harm others is often motivated by comparison shopping, assessing what others have relative to our own status. The most primal starting point for comparison shopping is the world of hierarchies, a world where the desire to dominate rules.
In social insects, fish, lizards, birds, rodents, whales, apes, or humans, males are bigger and bolder, more boisterous, brash and brazen, and more motivated to get into a brawl than females. Though biologists don’t define the sexes based on these differences, they use them to understand what drives competition for valuable resources and what determines the criteria for dominance status. Biologists define the sexes based on differences in the gonads, the reproductive organs that generate eggs and sperm, and the corresponding effects of sex-specific selection on the mind, body, and behavior. Females are those with larger, more costly gonads, where cost is defined on the basis of how much energy is invested in production. Think eggs versus sperm. This difference sets up an immediate competition, especially for species that have parental care. Once you invest in a big expensive egg, you don’t want to lose your investment. You want to protect it, avoiding harm and minimizing risk. On the other hand, if your investment is small, as is the case for sperm, you are not only freer to take risks, but favored by selection to do so.
These ideas about sexual selection started with Charles Darwin. One hundred years later, they were developed in detail by the evolutionary biologist Robert Trivers. Combined, they provide an explanation for why, in most species including our own,