Alix Spiegel: There's a man named Bob Rosenthal. He's a research psychologist. And early in his career, he did this thing. He went into his lab late at night and hung signs on all of the rat cages. And some of the signs said that the rat in the cage was incredibly smart. And some of the signs said that the rat in the cage was incredibly dumb, even though neither of those things was true.
Bob Rosenthal: They were very average rats that you would buy from a research institute that sells rats for a living.
Alix Spiegel: So then Bob brings this group of experimenters into his lab, and he says, for the next week, some of you are going to get these incredibly smart rats. And some of you are going to get these incredibly stupid rats. And your job is to run your rat through a maze and record how well it does.
Lulu Miller: Can you just pick up the rat?
Alix Spiegel: So, Ira, we actually did a very lo-fi, unscientific version of this in that little room in NPR.
Ira Glass: They let you do that?
Alix Spiegel: We didn't ask permission.
Ira Glass: Is that OK to do?
Lulu Miller: Yeah.
Alix Spiegel: Yeah.
Lulu Miller: And you've probably already guessed where this is going.
Alix Spiegel: Yeah. In Bob's real study, the experimenters ran the rats that they had been told were smart.
Lulu Miller: She has sort of an intelligent looking face.
Alix Spiegel: And the rats they had been told were dumb.
Alix Spiegel: It was not even close.
Bob Rosenthal: The results were so dramatic.
Alix Spiegel: In Bob's real study, the smart rats did almost twice as well as the dumb rats.
Ira Glass: Wait, even though they were the same?
Alix Spiegel: Yeah, even though the smart rats were not smart and the dumb rats were not dumb. They were all just the same average kind of lab rat. It was so shocking, people didn't really believe him.
Bob Rosenthal: I was having trouble publishing any of this.
Ira Glass: And so what was going on? Like, what was actually happening to make the rats do this?
Alix Spiegel: So what Bob figured out was that the expectations that the experimenters carried in their heads subtly changed the way that the experimenters touched the rats, and that changed the way that the rats behaved. So when the experimenters thought that the rats were really smart, they felt more warmly towards the rats. And so they touched them more gently.
Bob Rosenthal: We do know that handling rats and handling them more gently can actually increase the performance of rats.
Ira Glass: And how does this play out when it comes to people? How do our expectations of other people work?
Alix Spiegel: Well, what you saw in the rats totally holds for people too. I talked to Carol Dweck, who's a psychologist and researcher at Stanford.
Carol Dweck: You may be standing farther away from someone you have lower expectations for. You may not be making as much eye contact. And it's not something you can put your finger on. We are not usually aware of how we are conveying our expectations to other people. But it's there.
Alix Spiegel: And it happens in all kinds of areas. Research has shown that a teacher's expectations can raise or lower a student's IQ score, that a mother's expectations influences the drinking behavior of her middle schooler, that military trainers' expectations can literally make a soldier run faster or slower. So my question was-- you know, how far does this go?
Alix Spiegel: So Carol, clearly these expectation effects exist on a continuum. So for example, if I expect that if somebody jumps off a building, they will be able to fly, that's not going to work out so well, right?
Carol Dweck: Mm-hmm.
Alix Spiegel: So what does science know about where we should draw the line? Does it have a clear sense of that?
Carol Dweck: No. That line is moving. As we come to understand things that are possible and mechanisms through which a belief affects an outcome or one person affects another person, that line can move.
Ira Glass: Well, from WBEZ, Chicago, it's This American Life. Today on our program, we have a kind of hard to believe example of what expectations can do to people. This story is from a new radio show and podcast that Alix and Lulu are launching this week. It's called Invisibilia. It's about the invisible forces that shape human behavior, like beliefs and assumptions and emotions, which I know sounds a little abstract. But in execution, I have to say it is anything but.