Part of our job here is to make you smarter, so here are excerpts from a radio interview with Gary Marcus, a psychology professor at New York University. For more about the predisposition toward violence, get hold of a book by Richard Rhodes called Why They Kill.

Well, there are lots of behaviors that are tied to genes, but they’re not tied as closely as some people might think. So, the popular way of thinking about genes is that you have a gene for a particular trait. There’s a wonderful cartoon that talks about a gene for delusions of stock market grandeur. But, we don’t really have a gene for delusions of stock market grandeur, but we do have genes that affect all kinds of aspects of our personality. They do that by working together with other genes and by working with the environment. So genes don’t really dictate things. They give us options. They give us opportunities. And they can influence us. Push us a little bit in one direction or another …

There’s a great example, which I actually talked about in an op-ed in the L.A. Times last week. There’s a particular gene that causes a predisposition for violence, but only for people that are raised in abusive families. So, if you have the particular version of the gene, you can think of it as giving you two different strategies, one of which isn’t particularly violent, the other of which is. And, it’s actually the environment that brings out the aggression.