Disinhibition in The Gravity Error?

Increasingly flexible deployment of behavior is a hallmark of cognitive development - but even as adults, it can be difficult to overcome our habits. For children, this difficulty is even more pronounced. One classic demonstration of this difficulty comes from the gravity error, in which children are presented with an apparatus like the one pictured here; a ball may be dropped into one of three pipes, each of which "snakes around" before arriving at one of three locations at the bottom of the apparatus. The task is to find the location of a ball after it is dropped into one of the pipes. Successful performance requires that children overcome the prepotent tendency to assume the ball drops straight down, called the "gravity error," and instead to use their knowledge of the structure of the pipes to direct their searching.

Consistent with the idea that the overcoming prepotent responses is a relatively late-developing ability, many children younger than 4 show robust "gravity errors" on this task, in which they mistakenly search in the location directly underneath the location where the ball was originally dropped regardless of the pipe structures. In contrast, many children older than 4 are able to search in the correct location for the ball.

What mechanisms allow subjects to overcome the gravity error and ultimately search in the correct location? One account posits that increasing ability to inhibit competing representations is the major agent of change. According to this view, children who succumb to the gravity error are unable to inhibit searching directly below the location in which the ball was released.

Authors Freeman, Hood and Meehan set out to test this inhibition hypothesis with the following logic: if the youngest children who succeed at this task are able to do so because they inhibit a tendency to search directly below the release location, they should be also more likely to avoid searching in that location if they're told to avoid finding the ball. Instead, these children would be more likely to search in a third, neutral location than in the location directly below the ball (hereafter the "gravity location"), even though either location would be a safe choice in a task where they had to avoid finding the ball. The authors predicted this pattern because searching in the "gravity location" would involve disinhibition of the inhibition previously directed at that location.

Accordingly, Freeman et al. found that a majority of 4 year olds showed exactly this pattern. By the age of 5, however, a majority of children showed exactly the opposite pattern. And by 7 years of age, children showed no tendency to reach preferentially for either correct location in the avoidance task. What can be made of these results?

Freeman et al. argue that at 4 years, children must inhibit the gravity location in order to succeed at the original task. Then, when told to avoid finding the ball, they still avoid reaching to the gravity location even though that would be the safest place to search in an avoidance task. Instead, they search at a neutral location that does not require this effortful disinhibition. In contrast, the authors suggest that 5 year olds are aware that the gravity location is the "safest" choice in the avoidance task, and 7 year olds are aware that both locations are correct and thus there is no need to preferentially reach to one location or the other.

Are there alternative explanations?

One view is that because of the way the tasks were structured (continually alternating back and forth), the youngest children may actually have had difficulty in switching their behavior between avoiding the ball's true location and approaching the ball's true location. According to this view, repeated task-switching could result in interference for both the gravity location and the ball's true location. This possible alternative could be address by using a blocked design, in which one would expect an even stronger trend in the same direction if disinhibition is difficult for 4 year olds.