You know when you have a decision to make, the standard advice is to think everything through and weigh the pros and cons and reason your way to the right choice. But today we have a story about the limits of our rational minds to help us make decisions. It comes to us from our friends at Radio Lab.

(Soundbite of music)

JAD ABUMRAD: Hey, Steve.

INSKEEP: Thats Jad Abumrad of WNYC.

ROBERT KRULWICH: And this is me, Robert Krulwich.

INSKEEP: Oh, sorry, Robert, didnt mean to leave you out. Robert Krulwich as well.


INSKEEP: Okay, now, before we get started, remind us what Radio Lab is.

ABUMRAD: Radio Lab is a show where we explore big ideas that make us rethink ourselves.

KRULWICH And also the world all around us.

ABUMRAD: Right, and today were thinking about, as you said, how we make decisions. So Steve, let me just get things started by asking you - how many numbers do you think you can remember at once?

INSKEEP: I have no idea. Test me.

ABUMRAD: All right. Ready?


ABUMRAD: Four, six, one, seven, eight, two, three, 33

KRULWICH: This always a trick question with him.

ABUMRAD: Zero...

INSKEEP: Four, six, seven, one, eight, two, three, 33, nine, one, and then after that I dont know what it is.

KRULWICH: Thats good, actually, because, you know, I can do four, seven.

(Soundbite of laughter)

ABUMRAD: Robert is a special case, but it turns out theres a classic study in psychology that asks this very question. It happened in 1956, there was a psychologist named George Miller who asked people to memorize a bunch of different stuff - numbers, letters, musical notes - and what he found is that the average human being can hold about seven items in their short-term memory, seven.

INSKEEP: Like a phone number?

ABUMRAD: Exactly. Now the interesting thing is what happens to our decision-making powers when you try and get more than seven in your head.

KRULWICH: Hmm, what?

Unidentified Man #1: You want me to shut the door?

Unidentified Man #2: Yes...

ABUMRAD: Well, let me introduce you to someone.

Professor BABA SHIV (Stanford Graduate School of Business and Marketing): Im Baba Shiv, a professor here at the Stanford Graduate School of Business and Marketing. A lot of my research has to do with the brain.

ABUMRAD: And tricking people.

Prof. SHIV: Oh yeah, absolutely.

(Soundbite of laughter)

KRULWICH: (Unintelligible) I want to you to tell about one particular experiment that he did.

Prof. SHIV: So the experiment its pretty straightforward.

ABUMRAD: It goes like this. He got a bunch of subjects together. He said, okay, Im going to give you all a number.

Prof. SHIV: A number

ABUMRAD: on a little card, youre going to read the number, and I want you to commit that number to memory.

Prof. SHIV: Take as much time as you want to memorize the number.

ABUMRAD: Then he says

Prof. SHIV: Youre now going to walk to the next room and recall the number. And thats what subjects think. The subjects think that theyre going to be doing in that study.

ABUMRAD: They know that they are going to be in one place getting a number, going to another place, reciting that number.

Prof. SHIV: Thats right.

ABUMRAD: Thats all they know.

Prof. SHIV: Thats all they know.

KRULWICH: What they dont know is that not everybody is getting the same kind of number.

Prof. SHIV: Some people get a seven-digit number, some people get a two-digit number.

Prof. SHIV: That I can do by the way. I think I can do two digits.

ABUMRAD: No, I doubt it.

(Soundbite of laughter)

ABUMRAD: All the subjects have to do is theyve got to memorize the number, walk out of room one down the hall, room two, then recite their number. Now, just imagine. You with me?

Prof. SHIV: Mm-hmm.

ABUMRAD: Person with a two digit number in the head is walking out of room one.

Unidentified Woman #1: One, two is my number. I can definitely remember this.

ABUMRAD: Down the hall, same time someone with seven digits in their head

Unidentified Man #3: 1228932

ABUMRAD: Walks down the hall.

Unidentified Man #3: 289

ABUMRAD: Now, heres where the trickery comes in. As theyre walking down the hall, memorizing, all of a sudden

Unidentified Woman #2: Excuse me.

Unidentified Man #4: Oh.

ABUMRAD: ...they pass the lady in the hallway, and shes holding something.

Unidentified Woman #2: Sorry to interrupt you, but would you like a snack?

Unidentified Woman #1: Um

Unidentified Man #3: Sure.

ABUMRAD: She says, here, have a snack just as our way of saying thanks for participating in the study. You can have one of two snacks. You choose

Unidentified Woman #2: You can choose between either A) a big fat slice of chocolate cake, or B) a nice bowl of fruit salad.

ABUMRAD: Meanwhile, theyve both got these numbers still in their head. Now, heres the weird thing. When they finally make their choice

Unidentified Woman #2: What would you like? Some yummy cake

Unidentified Man #1: Hmm.

Unidentified Woman #2: ...or some healthy fruit?

ABUMRAD: The people - the people, this is crazy - the people with two digits in their head

Unidentified Woman #1: You know, I love cake but I think Ill take the fruit.

ABUMRAD: Almost always choose the fruit.

Unidentified Woman #1: Its healthy.

ABUMRAD: Whereas the people with seven digits in their head almost always choose the cake.

Unidentified Man #3: You know, the cake. I want the cake.

ABUMRAD: And were talking by huge margins here.

Prof. SHIV: It was significant. I mean, this was like in some cases, 20, 25, 30 point difference.

KRULWICH: So what does

ABUMRAD: Meaning if you have seven digits in your head you are twice as likely to choose cake than fruit, twice.

KRULWICH: So lets give them

(Soundbite of laughter)

KRULWICH: So the people with the seven digits get the cake. I get that part. I dont know why.

ABUMRAD: That doesnt interest you? As to why they would choose

KRULWICH: Well, yeah, why?

ABUMRAD: Okay, good.

(Soundbite of laughter)

ABUMRAD: Now that Ive got your interest, Ill tell you the theory.


ABUMRAD: And this is where it gets interesting. It seems that the brain is anatomically organized into different systems.

Mr. JONAH LEHRER (Science Writer): Dual systems is what theyre called.

ABUMRAD: Thats Jonah Lehrer, science writer, who we often call when talking about brainy stuff. According to Jonah, you have a rational deliberative system which is sort of more to the front of the brain, and then deeper in the brain you have an emotional unconscious system. According to Jonah, these two systems are often at war.

Mr. LEHRER: Theres constant competition between the rational brain and the emotional brain. Theyre always competing for attention and to guide and direct your behavior.

ABUMRAD: Especially when you have a tough choice like Baba Shivs cake versus fruit. There the competition is fierce.

Prof. SHIV: The emotional automatic system is just pushing them towards the cake.

ABUMRAD: The emotional brain loves sweet gooey chocolate cake.

Unidentified Man #4: Chocolate frosting.

ABUMRAD: Thats really what you want.

Unidentified Man #4: Give me a chocolate now.

ABUMRAD: On the other hand

Prof. SHIV: The deliberative system on the other hand comes and says wait a second.

Unidentified Man #5: Im thinking about this choice carefully.

Prof. SHIV: This probably is not good for you because

Unidentified Man #5: Calories, sugar, high fat content.

Mr. LEHRER: Think about your waistline.

Unidentified Man #5: Its going to make you chubby.

Mr. LEHRER: Think about your cholesterol.

Unidentified Man #5: It is not good for your health. It is not good for your self esteem.

Prof. SHIV: And that acts as a check.

ABUMRAD: But if you give that rational deliberative system seven numbers, just seven to memorize...

Unidentified man #5: 1228936, 12285, 122, one, a cholest 122...

ABUMRAD: Suddenly the rational brain has clearly too much to keep track of.

Unidentified Man #5: Or 2

ABUMRAD: Its getting tired.

Unidentified Man #5: 2

ABUMRAD: It cant put up as much of a fight.

Unidentified Man #5: Oh.

Prof. SHIV: Which means greater likelihood that the emotions will drive their choices.

ABUMRAD: The astounding thing here, says Jonah, is not simply that, you know, sometimes emotion wins over reason. Its how easily it wins. Seven numbers is all it takes to screw up reason.

Mr. LEHRER: Just think about how astonishingly limited that is.

KRULWICH: Yeah, I mean, compared to emotion, team reason is, well, pretty feeble.

Mr. LEHRER And what we always rely on it, all the advice on decision making is stop and think, slow down, take your time, and yet when you actually look at the brain, that can lead you to rely on a feeble piece of machinery.

INSKEEP: Oh, okay, well, Ill just set aside this cake and thank Robert and Jad for stopping in. Thank you, gentlemen.

(Soundbite of laughter)

ABUMRAD: Sure thing.

KRULWICH: We kind of knew youd do the cake.

INSKEEP: Thats Jad Abumrad and Robert Krulwich from the show Radio Lab, a production of WNYC in New York. You can explore Radio Lab at

Copyright © 2010 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by a contractor for NPR, and accuracy and availability may vary. This text may not be in its final form and may be updated or revised in the future. Please be aware that the authoritative record of NPR’s programming is the audio.



Please keep your community civil. All comments must follow the Community rules and terms of use, and will be moderated prior to posting. NPR reserves the right to use the comments we receive, in whole or in part, and to use the commenter's name and location, in any medium. See also the Terms of Use, Privacy Policy and Community FAQ.

NPR thanks our sponsors

Become an NPR sponsor

Support comes from