万圣节糖较少的孩子更快乐？

STEVE INSKEEP, HOST: Oh, there will be many ghosts and ghouls walking around tonight as trick-or-treaters take over America's streets. But underneath the costumes are human beings, which means they're driven by human psychology. And NPR's Shankar Vedantam, who comes by each week to tell us about social science research, has some research this week on what really makes trick-or-treaters happy. Hi, Shankar.

SHANKAR VEDANTAM, BYLINE: Hi, Steve.

INSKEEP: OK. Isn't this kind of obvious - what makes trick-or-treaters happy is candy?

VEDANTAM: That's right, Steve. And more candy is better, right?

INSKEEP: OK.

VEDANTAM: Well, it turns out that that might not actually be the case. So, researchers ran...

INSKEEP: What?

VEDANTAM: Researchers ran this very interesting study some years ago on Halloween night where trick-or-treaters showed up at the door, and some of them were given this wonderful, great candy bar, and others were given this great candy bar and a piece of bubble gum. Now, in any rational universe, you would imagine that the kids who got the candy bar and the bubble gum would be happier than the kids who got just the candy bar. I spoke with George Wolford. He's a psychologist at Dartmouth College. And along with his fellow researchers, Amy Doe and Alexander Rupert, they found something quite different. Here's Wolford.

GEORGE WOLFORD: Those children that got both the full-sized candy bar and the bubble gum second rated how delighted they were to get these treats lower than those people that got the candy bar only.

INSKEEP: Whoa, whoa, whoa, whoa, whoa. So, you're saying if you get less, you are actually happier, even though you would assume the bigger bag of treats would be what would make people happier.

VEDANTAM: That's right. And I can feel the anger of America's children streaming at me right now as I say this, Steve. But to understand what actually is going on, we have to go back even further into the crypt to an earlier study done by Daniel Kahneman. Wolford calls this one of his favorite studies in all of psychology. And we have to switch topics from Halloween to colonoscopies.

(LAUGHTER)

INSKEEP: Of course. What's going on here? Help me out.

VEDANTAM: So, Kahneman recruited a bunch of doctors to conduct a study among patients getting colonoscopies. Some of the patients got the regular colonoscopy - uncomfortable, unpleasant procedure - and the others got the same uncomfortable and unpleasant procedure, but at the end of it, the doctors didn't remove the tube from the patient's bodies. They actually left the tube in there a little while longer. Now, again, in any rational world, you would imagine that the patients that got the colonoscopy with the extra discomfort would rate their overall experience as being more painful and more unpleasant. But Kahneman found this actually was not the case, that the patients who got the extra discomfort actually thought the colonoscopies, as a whole, went better, and they were more likely to show up, then, for follow-up treatment.

INSKEEP: Suddenly, I'm wondering: Is that because they think it's supposed to hurt? And if it hurts really bad, maybe it's doing what it was supposed to do.

VEDANTAM: Well, it actually comes down to the order in which these things happen. And that's the connection with the Halloween candy study. With the Halloween candy study, the kids got the great treat first, and then a lesser treat afterwards.

INSKEEP: Oh, let down.

VEDANTAM: Exactly. Whereas, with the colonoscopies, they got the unpleasant procedure first, and then they got something that was slightly less unpleasant afterwards. And it turns out that when we think about experiences, Steve, we don't think about the experience as a whole. We're significantly biased by how the experience ends. So, if we have a great experience, Steve, that starts to go downhill, we rate the overall experience as being less good. Whereas if something starts out terribly, and then starts to get better toward the end, we rate the overall experience a little bit better. Wolford actually has a theory to explain this.

WOLFORD: If you're in a painful experience and it's getting better, then there's a sense in which things are improving. So, what you're judging is the trajectory. With positive goods, if I'm going from a nice treat to a lesser treat, the trajectory is going the wrong way.

INSKEEP: OK. So, if I get a candy bar, and then they throw in some bubble gum, it's like, oh, that's kind of a letdown. But you're suggesting - the implication here is if I get some bubble gum, and then they add a candy bar, that might be awesome.

VEDANTAM: Exactly right. So, the order in which you receive the treats is very important. If you get the lesser treat first and the nicer treat second, you're likely to be very happy. But if you get the nice treat first and the lesser one second, you're likely to be more dissatisfied with the overall experience. By the way, this has been found in a number of other settings, as well. Wolford conducted an experience with DVDs, and he found that when you give people a DVD of a very nice movie and then follow it up with a movie that was less good, people are less satisfied than if you just gave them the great DVD upfront.

INSKEEP: Shankar, thanks very much.

VEDANTAM: Thanks, Steve.

INSKEEP: That's NPR's science correspondent Shankar Vedantam. And we'll find out the end of this interview makes you happier than the beginning, I suppose, when you contact him on Twitter. He's @HiddenBrain. You can also talk to this program: @MorningEdition, @NPRInskeep, @NPRGreene.