God Soul Mind Brain

proposition that people can examine rationally; it is a link, forged mainly during your upbringing, that connects the sight of a face to a tinge of negative emotion.

    Advertisers bow to the amygdala, although they may not know it by name. The image of an attractive, scantily clad woman prods the sex nucleus in the hypothalamus. Photograph her holding a beer, and show the picture to a man a few times, and soon his amygdala learns a new link. When he thinks about beer, or sees a beer, he feels just a little bit sexy. The connection from his cortex (which processes the image and the thought of beer) to his hypothalamus sex nucleus is burned straight through his amygdala. That slight sexy tinge of feeling he has in reaction to beer has nothing to do with rational thought. He may not even remember seeing the ad. No matter; it still has its effect.

    We tend to think that our convictions are absolute. We look inside of ourselves, examine the tendrils in the amygdala that have grown up organically as a result of our particular training history, and we think that we have found access to universal truth.

    For example, a fundamentalist might hold in his cortex for a moment the thought of homosexuality. A link in his amygdala activates the anger and disgust and dread centers in his hypothalamus. These centers send output widely around the brain and body, the heart, the gut, the skin, and his cortical mechanisms for perception receive that emotional signal. He says, “Homosexuality is wrong. I know it, I am convinced of it, because I feel it in my heart, in my gut. I sense it to be true.” But what he feels is not a universal truth. His brain has no access to a repository of celestial truths. He is experiencing the consequence of a learned connection in his amygdala. Although he may invent rationalizations after the fact, intellectual reasons to support his moral conviction, the reasons are peripheral. At the center of his belief is a perception that homosexuality is wrong and disgusting. He perceives the emotional consequence of his amygdala tapping his hypothalamus.

    Someone else, with a different training history and therefore a different set of connections through the amygdala, arrives at quite the opposite moral conviction and is convinced of the principle of equal rights.

    My point here is not whether one or the other conviction is more constructive (my sympathies are decidedly with the egalitarian point of view), but that neither side represents a fundamental moral truth of the universe. There are no fundamental moral truths of the universe. Morality is not defined outside of us; it is a physiological construct of the brain.

    The brain basis of morality is an emerging area of study. Scientists such as Green and Cohen have begun to pioneer the topic. At its core is the realization that when we plumb inwardly for moral truth, we follow a specific process of firing up thought X and assessing its emotional tinge. We may say to ourselves, “On deep reflection, I realize that X is wrong,” or, “X is right.” But the inner reflection does not reveal anything about a moral framework of the universe. Instead, the inner reflection is a way of assessing our own quirky, culturally and personally learned emotional associations.

    The trainability of the amygdala was originally studied in rats. For example, as Ledoux showed, it is possible to train a rat to fear a red light by shocking the rat’s foot every time the light turns on. If the rat’s amygdala is then damaged, the link disappears and the rat no longer fears the light. Therefore the link between perceiving a red light and experiencing fear runs through the amygdala. If your foot were shocked every time a light turned on, your amygdala would learn the same connection. To some extent you train up your amygdala in this way, through life’s various metaphorical foot shocks and reward pellets.

    The most useful property of the amygdala, however, is not that it can be trained by reward and punishment, but that it can learn through socialization. We believe what the people around us believe. We believe what we are taught. Above all, we believe what we see others believing . This tendency for beliefs to spread by social imitation is the topic of the final chapter.

Chapter 10

    Memes and the brain

    From gods and spirits, perhaps not surprisingly, this book has come to the general topic of human culture. My goal in this final chapter is to explore briefly how brain