Study Suggests Hand Washing Cleanses The Mind

IRA FLATOW, host:

This is SCIENCE FRIDAY from NPR. I'm Ira Flatow.

How many times have you heard the expression - maybe you've used it yourself: I'm going to wash my hands of something. I'm going to move on, I'm going to disassociate myself from something, I'm washing my hands of this. And this idea of symbolically washing yourself clean is something you see in religion too, of course, like the ritual of baptism.

But could there be a little more to the metaphor? Could washing your hands, the act of methodically lathering up with soap and water, have some tangible effect on your thoughts? A study out this week in the journal Science suggests that the answer is yes, that hand washing can actually change your thinking.

Well, my guest is the lead author of that study. He joins us now to tell us more about that phenomenon. Spike Lee is a graduate student in the Department of Psychology at the University of Michigan in Ann Arbor. He joins us by phone. Welcome to the program.

Mr. SPIKE LEE (Graduate Student, University of Michigan): Thank you so much for having me, Ira.

FLATOW: You're not the moviemaker, right?

Mr. LEE: I am not, unfortunately.

(Soundbite of laughter)

FLATOW: Tell us. How did you get this idea for this hand washing study?

Mr. LEE: I really like how you began the program, by sort of reminding us that there is this religious connotation or religious connection to the washing-away-your-sins metaphor, because that metaphor was actually what motivated us to do this research.

You know, several years ago there was a line of studies that showed that the physical sense of purity is actually related to the moral sense of purity in the human mind.

When we looked at the idea, the metaphor, washing away your sins, we thought, well, okay, that suggests that we should take metaphors much more seriously than we tend to. But what about the broader metaphor? Maybe washing away your sins is just a specific case of a broader phenomenon where people can wipe away, wipe the slate clean, wipe away all kinds of past concerns, not just moral concerns.

And that's why we wanted to test this idea with a classic socio-psychological phenomenon called cognitive dissonance.

FLATOW: Cognitive dissonance.

Mr. LEE: Right.

FLATOW: And so you did experiments with trying to figure out whether washing your hands affects your thinking or not.

Mr. LEE: Exactly, and here the sort of thinking that we care about is the discomfort that people have when they have to make difficult decisions. So think about, you know, choosing where to go for summer vacation, let's just say Paris or Rome, like I did last year...

FLATOW: We should all have those decisions to make, but go ahead. I don't mean to interrupt. Go ahead.

(Soundbite of laughter)

Mr. LEE: And you have to go to one of them in the end. And suppose you choose to go to Paris - here people want to feel that they made the right choice. How do they do that? Well, they focus on the positive features of Paris, the chosen option. They think about how fantastic the French cuisines are, and the art museum is gorgeous and so forth. In comparison, Rome is historically rich, but it's just not as exciting.

So essentially people are focusing on the positive features of the chosen option and the relatively negative features of the rejected option. And as a consequence, they come to like the chosen option even more after they make the choice, compared to before they make the choice. This is called choice justification.

What our studies showed was that when people are not given a chance to wash their hands, they show this classic pattern, you know, as found in hundreds of previous studies. But once you give them a chance to wash their hands, they no longer have any choice justification tendency. They do not feel the need to say to themselves: I made a right choice.

FLATOW: So if you give them the choice again, do they make the same choice, or could be a different choice?

Mr. LEE: That we did not test. What we did test, though, was the expected quality of - using our example, you know, how much do you expect to enjoy Paris compared to how much you can expect to enjoy Rome. So we asked people about the expected quality of consuming certain products, such as CDs and fruit jams.

FLATOW: Right, and you found that the act of washing your hands affects your choice. Does it make you rethink - or is it the act of just standing there, does it make you think about things, or does it make you focus on something else totally, like washing your hands, and that may affect your choice?

Mr. LEE: Right. It's a very interesting thought. I think that it not only distracts you a little bit, I think that it does have this feeling of removing past concerns, and it allows you to sort of move on, and the reason is metaphorical connection.

Now, think back about the washing-away-your-sins metaphor. Psychologically what seems to be happening is that the physical experience of removing germs or dirt or contaminants on your hand is used to provide a basis for an abstract kind of experience, removing residues from your past immoral behaviors. So that's in the case of morality.

Now, in the case of choice, it seems that when people are washing away things, physically washing away things off their hands, they're also abstractly washing away mental residues from their past decisions. So I think that that is what's going on, and that's why it has the power of freeing people from concerns about past decisions.

FLATOW: So you're saying it is the actual, the water that's important here. So if you were distracted by playing with a Rubik Cube or chopping vegetables for dinner that night, you would not expect the same reaction, the same...

Mr. LEE: We would not expect the same reaction. You're absolutely right. And in fact, in the honor group that did not wash their hands, in some ways they were distracted because they were looking at a bottle of hand soap, evaluating the, you know, how attractive they found the bottle of hand soap and so forth. So they were distracted by other thoughts.

The only difference for the hand-washing group was that they actually tested a product with water and soap.

FLATOW: And you also said that it worked with hand wipes also.

Mr. LEE: Yeah. Yeah, yeah, yeah, absolutely. In the second study we used antiseptic wipes. The idea was fairly similar. We had half the people look at a packet of antiseptic wipes and tell us how much they liked the design and so forth. The other group also tested it by actually wiping their hands clean.

FLATOW: So are you saying that this morality factor, is that built into us, washing our hands of something, or is it something that we learn and we pick up as we get older?

Mr. LEE: I think that there's - chances are that people learn it, because the human mind works like this. There are thoughts that are intangible, they are very difficult to grasp. Morality is a complex phenomenon, and it seems that in the past few years there's been increasing research suggesting that for complex ideas, abstract thoughts like these, we rely on the physical experience to help us make sense of them.

And by relying on this experience, of course you have to first have those experiences. So I think it's sort of a learning process over an individual's life history.

FLATOW: Let me get a quick call in from Ryan in Boulder. Hi, Ryan.

RYAN (Caller): Hello.

FLATOW: Hi there, go ahead.

RYAN: I just had a quick question about the experimental controls. When the subjects washed their hands, was there a mirror present?

Mr. LEE: I'm sorry?

FLATOW: Was there a mirror? Were they able to look in a mirror while they were washing their hands?

Mr. LEE: They weren't. It was just a sink. They weren't able to actually look at themselves washing their hands.

RYAN: Okay, just simply because I know that in other socio-psychological studies, the presence of a mirror has also changed their decision-making. So it was just a quick question.

FLATOW: Good question, Ryan.

Mr. LEE: Right, you're absolutely right. Making yourself salient(ph) does change people's decision-making quite often.

FLATOW: And so where do you go from here? How can you further this study? What else would you like to know, knowing this?

Mr. LEE: There's something that I've observed in this culture that really fascinates me. You know, if we take the metaphor cleaning - wiping the slate clean very seriously, it shouldn't be just about negative past feelings. It should also apply to positive feelings.

I've heard examples like sometimes when we shake hands with a famous person, we don't want to wash our hands afterwards. And also, although I didn't grow up in America, I know that in this culture there are these baseball players who refuse to wash their lucky socks. Why is that?

FLATOW: That's a superstition. Baseball players are very superstitious. They won't shave. They won't shave if they're in a hitting streak or, you know, things like that.

(Soundbite of laughter)

Mr. LEE: I heard that too. I mean, I play basketball myself, but I do wash my socks. Maybe that's why I don't have that much luck so far.

(Soundbite of laughter)

Mr. LEE: But the interesting thing is, in the morality case or in our choice case is also in some ways superstitious. There's no obvious reason why we have to scaffold(ph) our understanding of abstract thought on physical cleaning.

So I think that wiping the slate clean might wipe away not only negative experiences but also positive experiences. So people might actually avoid washing their hands after they've done something nice, glorious.

FLATOW: You say it's normal to go through this sort of justification phase after making a decision, but suppose we skip that part by washing our hands, maybe. Could that be a problem down the line?

Mr. LEE: I think so. In our studies we measured people's expected quality of the products, right, expected quality of the CDs and expected taste of the fruit jams. Now, we didn't actually measure people's consumption of those products.

So what intrigued us is this idea that, well, perhaps there is negative long-term consequences of washing. So without doing the mental work of justifying the choice, maybe further down the road people will be less likely to enjoy what they buy, and that could be a problem, because, you know, we make decisions and choices, tens and hundreds of them every day. Because we cannot have everything in life, if our goal is to enjoy whatever we can have, then washing your hands might not do you a favor.

FLATOW: So don't wash your hands.

Mr. LEE: It depends on the goal, though, because if all of a sudden our goal changes to a short-term goal of having a fair assessment of different options available on your table, then remember the original pattern of choice justification is that you focus on the positive features of the chosen option and the relatively negative features of the rejected option.

In other words, you have a more biased view of these available options. Washing your hands allows you to have a more accurate, fair assessment of these options. So if that's the goal, washing your hands would do you a favor.

FLATOW: So if you're not sure about your decision, and you want to rethink it, then you should go wash your hands.

Mr. LEE: I think so, to the extent that you have not committed yourself to a certain choice, because choice justification kicks in when you feel that you have committed yourself to certain, to one option already. Just like, you know, I'm going to buy this car now, and you start thinking to yourself, oh yeah, this car really is more attractive and the power and efficiency and so forth, right. But if you haven't made that decision yet, I don't think that choice justification, the mental work, has started occurring.

FLATOW: So it's interesting that it's in both positive and negative. If you're feeling lucky, you don't wash your hands either.

(Soundbite of laughter)

FLATOW: That's kind of interesting. Thank you very much, Spike Lee, for taking time to be with us. Good luck to you. We'll be watching for your next experiments.

Mr. LEE: Thank you so much, Ira, for having me again. It's a pleasure.

FLATOW: You're welcome.

Mr. LEE: Bye-bye.

FLATOW: Have a good weekend. Spike Lee is a graduate student in the Department of Psychology at the University of Michigan in Ann Arbor.

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

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