In 2002, having spent more than three years in one residence for the first time in my life, I got called for jury duty. I show up on time, ready to serve. When we get to the voir dire, the lawyer says to me, “I see you’re an astrophysicist. What’s that?” I answer, “Astrophysics is the laws of physics, applied to the universe—the Big Bang, black holes, that sort of thing.” Then he asks, “What do you teach at Princeton?” and I say, “I teach a class on the evaluation of evidence and the relative unreliability of eyewitness testimony.” Five minutes later, I’m on the street.
A few years later, jury duty again. The judge states that the defendant is charged with possession of 1,700 milligrams of cocaine. It was found on his body, he was arrested, and he is now on trial. This time, after the Q&A is over, the judge asks us whether there are any questions we’d like to ask the court, and I say, “Yes, Your Honor. Why did you say he was in possession of 1,700 milligrams of cocaine? That equals 1.7 grams. The ‘thousand’ cancels with the ‘milli-’ and you get 1.7 grams, which is less than the weight of a dime.” Again I’m out on the street.
You might think that the things that get people to change their behavior are things that are memorable, that they can use their analytical brain to set down a long-term trace, or even just emotional, but surprisingly what we see is the brain regions that seem to be involved in successful persuasion. We can predict who will use more sunscreen next week based on how their brain responds to an ad today. The brain regions that seem to be critical to that are brain regions involved in social thinking, in thinking about yourself and thinking about other people. So this seems to be more about our identity and the identities that we’re capable of trying on. If I can’t try on the identity that you’re suggesting to me—being a sunscreen-using person, or a nonsmoker, or something like that—the ad is much less likely to stick.
William James said long ago that we have as many identities as people that we know, and probably more than that. We are different with different people. I’m different with my son than I am with you. We have these different identities that we try on, and they surround us… I’m really interested in looking at that as a mechanism of persuasion when it comes to regular old persuasion, when it comes to education, when it comes to public health, and when it comes to international issues as well. It’s finding that latitude of acceptance and finding out how to use it successfully.