Have you ever watched a white rat choose between an 8 and 32 percent sucrose solution by pressing two different bars on variable-interval schedules of reinforcement? No? Lucky you. I devoted two years of what would otherwise have been a misspent youth to running choice experiments with rats in Skinner boxes for my master's thesis on "Choice in Rats as a Function of Reinforcer Intensity and Quality." Boys gone wild!

Since then, the behaviorists' black box has been penetrated by neuroscientists, most recently by Read Montague of the Baylor College of Medicine with Why Choose This Book? (Dutton, 2006). Montague argues that our brains evolved computational programs to evaluate choices in terms of their value and efficiency: "Those that accurately estimate the costs and the long-term benefits of choices will be more efficient than those that don't."

Life, like the economy, is about the allocation of limited resources that have alternative uses (to paraphrase economist Thomas Sowell). It all boils down to energy efficiency. To a predator, Montague says, prey are batteries of energy: "This doctrine mandates that evolution discover efficient computational systems that know how to capture, process, store, and reuse energy efficiently." Those that do so pass on their genetic programs for efficient computational neural processing to make efficient choices. As a result, our brains consume only about one-fifth the energy of a lightbulb.

Unfortunately, these evolved computational programs can be hijacked. Addictive drugs, for example, rewire the brain's dopamine system--normally used to reward choices that are good for the organism, such as obtaining food, family and friends--to reward choosing the next high instead. Ideas do something similar, in that they take over the role of reward signals that feed into the dopamine neurons. This effect includes bad ideas, such as the Heaven's Gate cult members who chose suicide to join the mother ship they believed was awaiting them near Comet Hale-Bopp. The brains of suicide bombers have been similarly commandeered by bad ideas from their religions or politics.

Our brains evolved computational programs to evaluate choices in terms of their value and efficiency.

In The Science of Good and Evil (Times Books, 2004), I argued that we evolved moral emotions that operate similarly to other emotions, such as hunger and sexual appetite. Thinking of these emotions as proxies for highly efficient computational programs deepens our understanding of the process. When we need energy, we do not compute the relative caloric values of our food choices; we just feel hungry, eat and are rewarded with a sense of satisfaction. Likewise, in choosing a sexual partner, the brain employs a computational program to make you feel attracted to people with good genes, as indicated by such proxies as a symmetrical face and body, clear complexion, and a 0.7 to 1 waist-to-hip ratio in women and an inverted pyramid build in men. Similarly, in making moral choices about whether to be altruistic or selfish, we feel guilt or pride for having done the wrong or right thing. But the moral calculations of what is best for the individual and the social group were made by our Paleolithic ancestors. Emotions such as hunger, lust and pride are stand-ins for such computations.

How can we utilize this theory of choice to our advantage? Montague employed functional magnetic resonance imaging (fMRI) to discover that certain brands, such as Coke, "change dopamine delivery to various brain regions through their effect on reward prediction circuitry." The Coke brand has a "flavor" in the ventromedial prefrontal cortex, a region essential for decision making. Just as Coke is a proxy for flavor, hunger a proxy for caloric need, lust a proxy for reproductive necessity, and guilt and joy proxies for immoral and moral behavior, so, too, can we market moral brands to rewire brains to value and choose good ideas.

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