When a male vole repeatedly mates with a female, a hormone called vasopressin is released in his brain. The vasopressin binds to receptors in a part of the brain called the nucleus accumbens, and the binding mediates a pleasurable feeling that becomes associated with that female. This locks in the monogamy, which is known as pair-bonding. If you block this hormone, the pair-bonding goes away.

I know one lab that studies nicotine receptors and all the scientists are smokers, and another lab that studies impulse control and they're all overweight.

The first lesson about trusting your senses is: don't. Just because you believe something to be true, just because you know it's true, that doesn't mean it is true.

Some men may be genetically inclined to have and hold a single partner, while some may not. In the near future, young women who stay current with the scientific literature may demand genetic tests of their boyfriends to assess how likely they are to make faithful husbands.

Because vision appears so effortless, we are like fish challenged to understand water.

We're trapped on this very thin slice of perception ... But even at that slice of reality that we call home, we're not seeing most of what's going on.

To a space alien or a German Shepherd dog, two humans would be indistinguishable, just as attractive and unattractive space aliens and German Shepherd dogs are difficult for you to tell apart.