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.