As parents, we all have expectations for ours kids. For many of us, it seems like those expectations don’t matter at all, and no matter what, our children are likely to do whatever they want, regardless of what we want for them. But it turns out that our expectations are powerful motivators of children’s behavior, whether we realize it or not.

To illustrate just how powerful, let me begin by telling you about a classic study in psychology that is not about children, but about rats (because, well, most research in psychology starts with rats). In the study, undergraduates came into a lab and were told that they were going to be tasked with replicating a previous experiment. They were given one of two types of white rats, and over the course of a week, they were asked to train the rats to run a maze. Half of the students were told that they would receive “bright” rats, who, based on , should learn to run the maze quickly. The other half were told that they would receive “dull” rats who should perform more poorly on the maze than the bright ones. Overall, the bright rats did run the maze more successfully than the dull rats by the end of the experiment. Further, over the course of the five days, the bright rats showed evidence of learning, running the maze more successfully with each day, while the dull rats showed little or no improvement over time.

Sounds pretty unsurprising, right? What if I told you that there were no actual differences between the rats at the beginning of the study; the rats weren’t actually “bright” or “dull”, and there were no real differences between them, including their age or . How then, do we explain these results? The researchers concluded that because the undergraduates had different expectations about how the rats should behave, they handled the rats differently when training them to run the maze, in ways that matched their expected potential (Rosenthal & Fode, 1963). The effect—where expectations eventually translate into real differences in behavior—has since been dubbed the “Rosenthal effect.”

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You might be thinking to yourself, okay fine, but what does this have to do with kids? It turns out that the same researchers found similar effects in elementary school kids just a few years later. They didn’t ask children to run mazes; instead, they gave children in 18 different elementary school classrooms an test in the beginning of the school year. They then told the teachers that based on this test, the researchers had identified about 20% of kids in each classroom that they expected to “bloom” over the course of the school year and demonstrate a high level of academic achievement. The catch was, the 20% of children identified as “bloomers” were chosen at random—their IQ scores weren’t higher than the rest of the kids in their class. Nonetheless, at the end of the school year, the “bloomers” in each classroom were actually performing better and showed increases in IQ compared to their classmates. In other words, a sort of self-fulfilling prophecy was at work, and the students that were expected to succeed, in the end, did (Rosenthal & Jacobson, 1966).

Much more recent research echoes these findings. I’m sure you’ve heard somewhere that boys perform better than girls at math in school. This isn’t just an unfortunate myth, boys really do outperform girls at math in high school (Miller & Halpern, 2014). At much younger ages, girls perform just as well as boys in math, and even outperform boys in other subjects like reading. But, starting in kindergarten and first grade, parents expect that boys will outperform girls in math (Entwisle & Baker, 1983; Miller & Halpern, 2014).

You can imagine that if IQ can be affected by a teacher’s expectations about a child’s abilities, math skills should be no different. So it’s possible that one reason we start to see boys outperforming girls in math later in is that for years, we expect them to do worse. And in fact, in a recent study looking at the relationship between parents’ expectations and their child’s math performance, researchers reported that the more mothers thought that boys were better than girls at math, the worse their daughters felt about their own math ability (Tomasetto, Mirisola, Galdi, & Cadinu, 2015). What’s worse is that by the ripe old age of 6, girls are already becoming less and less interested in games for “smart” kids and are less likely than boys to say that members of their own are “really, really, smart” (Bian, Leslie, & Cimpian, 2017).

The point here is that our expectations for kids—whether we are aware of them or not—can actually affect their behavior. Sometimes we can’t help the expectations that we have, and we all have them. But knowing that our expectations might affect how our children behave and perhaps even how they learn suggests that maybe expecting the best isn’t such a bad idea. If we expect that our children or our students or even our friends are going to fail, we are in some way setting them up to fail. But instead, if we expect that they will succeed, we might be giving them exactly the kind of support they need to do just that.