Zelazo – preschool years

Because executive function refers to the deliberate, the processes involved in deliberate, goal-directed problem solving, it’s necessary to create more and more difficult problems in order to assess executive function at different ages, as children get older. And so one task that we’ve investigated quite extensively, is something called the dimensional change card sort which is quite useful for studying executive function during the preschool period, between, for example, about three and five years of age. 

And in this task children are shown target cards and then, for example, a red rabbit and a blue boat. And then they’re given a series of test cards that would be sorted differently depending on whether you were sorting by shape or by colour. So they match one target on one dimension, and the other target on the other dimension. And children are told to sort the cards, for example, first by shape, and then after they sort a card or two by shape, they’re told, “Okay, stop. I want you to play a new game. We’re not going to play the shape game anymore. Now we’re going to play the colour game.” 

In the colour game, red ones go over here, blue ones go over here. “Here’s a red one, where does it go?” And curiously, three-year-olds typically perseverate in that task. They persist in sorting by that initial dimension even though they’ve been told the new rules. And you can ask these three-year-olds, you can say to a child who’s persisting in sorting by shape, but now being told to sort by colour, you can say, “We’re playing the colour game now, right?” And they say, “Right”. And you say, “So where do the red ones go in the colour game?” And they point to the right box. And you say, “So what about this red one?” And they turn around and they sort it incorrectly by shape. 

So again, that’s a situation where you need to think flexibly, you need to keep the relevant rules in mind, you need to inhibit a tendency to persist in sorting according to the old dimension, and younger children have considerable difficulty with all three of those aspects of executive function. Whereas older children tend to behave correctly in that situation.