By Hannah Meyers

I try not to think too much about my brain. But Laurence Tancredi’s new book compels the reader to consider whether choices are simply shaped by the chemistry in our heads—and whether that makes us crazies, jerks or just human.

Tancredi writes in the nerdy authorial voice that marks a gifted scientist, but when we start hearing about psychopaths and love affairs, the book really heats up. Since the author is a psychotherapist by trade, he can draw on his patients for individual case studies. Ricky Green, for example, has some problems—in point of fact, he’s a psychopathic killer. Tancredi was brought in by the court to interview Green and determine the validity of his insanity plea. The narrative gets more and more gruesome as we hear about the homicides themselves, and then about Green’s childhood, which included a sodomizing grandpa and a rapist sister. Later on, Green married an abusive prostitute.

Tancredi builds his analysis of Green, starting with a picture of a pretty normal guy—just a little unhinged—and ending up with scary insights into the killer’s neurological shortcomings. It is explained that, “given the high probability of aberrancies in Ricky Green’s biology, as well as his dysfunctional family and personal histories, his behavior was heavily influenced by biological factors.” Which “affect not only how the brain processes information, but the scope of one’s ability to think about moral considerations.”

All the stories in the book—and there are many entertaining ones—turn on how those factors affect human behavior. For example, a woman comes in who has become involved in an affair with a co-worker, despite having sworn to herself that she never would. Tancredi explains that maybe she is not to blame, because “by finding the man attractive, the woman began a ‘rehearsal,’ which was intensified with every interaction, until the thought that could not be entertained had given rise to activation in parts of her brain before she was consciously aware of it.” This clearly has deep implications for the understanding of morality and individual will.

There is a good deal here about the brain’s chemistry as it relates to sex. In fact, “attraction between people is actually a chemical phenomenon that takes place in the brain. Recent studies point to particular neurotransmitters like dopamine…as largely responsible for mediating ‘chemistry’ or attraction between people.” Most of the data concerns humans, but prepare to be shocked by hormone levels in the brains of male prairie voles during orgasm.

After relationships in general and sex in particular, Tancredi turns to money: the dramatic patterns our brains follow when we think about cash. “Similar to cocaine’s effects on neurons, money is reinforcing as a reward to humans because we have given it this capacity to stimulate… money seems to act on more different pathways of the reward system than do natural rewards, such as food and water.” The plutocrat reading the Wall Street Journal is, chemically, little different from the fiend slavering after his bags of white powder—a comforting thought for at least some of our readers, no doubt.

Inevitably, Tancredi asks whether there is a distinction between people who commit horrendous crimes because they are bad people and those who do it because they are just mad, insane, and not responsible for their actions. After the discussion of how the brain develops and functions, the question seems all the more complex.

Lucky for us and for the world we live in, there is something called neuroplasticity – our brains’ ability to “adapt, by growing new neural connections or eliminating old ones, to changing conditions through learning, rehabilitation, and procedures.” Fortunately, as we can be wired (or wire ourselves) to do what is wrong and indisciplined and self-destructive, so can we wire ourselves to do just the opposite and become good, decent people who exercise, balance our checkbooks and call aged relatives faithfully—good news for all. Just as Jesus can be, Tancredi concludes, “Neuroplasiticity can be our best friend if we’ve gone wrong and want to reform.”

Hardwired Behavior: What Neuroscience Reveals about Morality

By Laurence R. Tancredi

250 pages, $28.99, (Cambridge)