THE DEVELOPMENT OF EXECUTIVE FUNCTION IN EARLY ...

Procedure. Testing took place in a quiet area at children's day care center or in a university laboratory, and all
procedures were videotaped. All children were tested individually in one 20- to 25-minute session. Children
were given 5-minute breaks between the tasks in order to minimize any interference or carryover effects. After
children were seated at the table and were comfortable with the experimenter and the setting, the experimenter
told the children a set of rules for separating the test cards.
In the standard version, two examples from a particular category (e.g., the brown car and the white plane from
the vehicle category; see Table 1) were chosen as target cards and affixed to the two sorting trays. During the
preswitch phase, children were first told one pair of rules (i.e., shape rules or color rules) for separating the test
cards, which consisted of 10 white cars and 10 brown planes. Children who sorted by color during the
preswitch phase were told: "If it's brown put it here, but if it's white put it there." In the course of explaining the
game, the rules were stated repeatedly in different ways. For example, children were told, "All the ________ go
here," "If it's __________ then it goes here," and "Only ____________ go here."
The experimenter then sorted one test card face-down into each tray to illustrate what children were supposed to
do. After these demonstration trials, preswitch test trials commenced. On each preswitch trial, the