Childhood adversity is thought by most experts to be bad for cognitive development: for instance, people who grow up in stressful environments tend to score lower on tests of memory and IQ. They also perform worse on tests of impulse inhibition, which in turn predicts success and competence in later life.

Now a new study suggests that the picture of how unreliable environments affect cognition is not purely one of harm. Wondering whether there might actually be benefits, psychologist Chiraag Mittal and his colleagues at the University of Minnesota ran a series of experiments in which they measured both inhibition and task switching.

In the inhibition test, the 103 adult participants had to try to ignore a flash on one side of a screen so they could identify which direction an arrow was facing when it flashed briefly on the other side. The switching test involved categorizing colored shapes by either shape or color, as instructed by a changing word on the screen. Being good at shifting means a person is able to let their responses be guided by the situation rather than an internal goal. It is an aspect of cognitive flexibility, which is thought to underlie abilities such as creativity.

The researchers assessed the participants' childhoods in terms of both “harshness” (using questions about socioeconomic status) and “unpredictability” (using degree of agreement with statements such as “People often moved in and out of my house on a pretty random basis”). They also included a condition where subjects were prompted to feel uncertainty via reading an unsettling news story, a well-established laboratory technique.

The results show that when participants felt uncertain, those who had experienced unpredictable but not harsh childhoods performed worse at inhibition but better at shifting than those whose childhoods were not unpredictable. The finding makes sense: inhibition is important for pursuing long-term goals and is thus most useful in stable environments, whereas the ability to shift rapidly among different demands would presumably be most useful in changeable environments. The implication is that kids who grow up in adverse environments are not impaired so much as shaped. “This is one of the first studies showing that early unpredictability shapes people's cognition adaptively rather than impairing it,” Mittal says.

There is much we do not yet understand about the mechanisms at work here, cautions Celeste Kidd, a cognitive scientist at the University of Rochester who also studies children's cognitive development. As a new finding, this study needs replicating, she says, but she is enthusiastic about the approach. “People don't usually think about these things in terms of adaptive processes,” Kidd says. “This is positing that there are certain abilities that are better developed through unstable environments than stable ones; it's very cool.”