THE DEVELOPMENT OF EXECUTIVE FUNCTION IN EARLY ...

year-olds have difficulty whenever they are required to use rules that span major branches in a hierarchical
tree structure. According to CCC theory, when children are asked to play the "red game" and then the "rabbit
game" with reference to a single stimulus, they must formulate a higher order rule, select a dimension (i.e., a
setting condition), and then select the appropriate rule.
EXPERIMENT 5
Experiment 4 demonstrated that 3- to 4-year-olds failed to switch flexibly even when they were required to use
a single pair of rules (as opposed to two pairs of rules in the standard DCCS). According to CCC theory, failure
on the Pruned Tree (single test card) version resulted from the inability to construct a higher order rule.
However, it is also possible that young children are simply incapable of sorting the same test card in two
different ways within an experimental context.
Experiment 5 was designed to test this hypothesis directly by presenting 3- to 4-year-olds with a version of the
DCCS in which only one dimension (e.g., color) was used: the Unidimensional (single test card) version.
Although the wording of the rules in this version was identical to the wording in the Pruned Tree (single test
card) version (i.e., "If it's the _______________ game put it here, but if it's the ________________ game put
it here"), CCC theory predicted that 3- to 4-year-olds would perform well on this version because only one
dimension, and therefore only one major branch of the tree in Figure 3, need be considered. In contrast,
however, if children were unable to sort a single test card in two different ways, either because of weak
inhibition or because of difficulty redescribing stimuli, then they would be expected to fail this version.
Method
Participants and design. Sixteen 3- to 4-year-olds (M = 41.7 months; range: 38 to 47 months; 7 girls and
9 boys) were recruited in the same fashion as in Experiment 1.
All children received two instances of the Unidimensional (single test card) version, one with color rules and
one with shape rules, in a counterbalanced order. In this version, the target cards were unidimensional (e.g., a
blue patch vs. a green patch, or an outline of a car vs. the outline of a flower). The test card, on the other hand,
displayed both values of the relevant dimension only (see Figure 10). For color rules, the test card was half
green and half blue. For the shape rules, the test card displayed the outline of a flower on one lateral side and
the outline of a car on the other lateral side. For each task, half of the children were required to first sort by one
level of the dimension (e.g., play the green game) and then switch to the second level (e.g., play the blue
game).
Procedure. The Unidimensional (single test card) version was administered in a similar fashion to the Pruned
Tree (single test card) version in Experiment 4. On test trials, children were shown the green/ blue card and told,
"If it's the green game put it here, but if it's the blue game put it here. Let's play the green (blue) game. Where
does this one go?" After the first task, children were given a brief intermission (approximately 2 minutes). Then
the second task was administered in an identical fashion (except with cards and rules from the other dimension).
The total procedure took approximately 10 minutes to administer.
Results
Group analyses. An initial repeated-measures ANOVA failed to detect any differences in number of correct
postswitch trials on the two sorts. Thus, to simplify the analyses and to keep them comparable to Experiment 4,
the results were averaged across both tasks. A one-way (Order) ANOVA was then conducted to test for possible
order effects. The analysis revealed no significant effect of order, and therefore this variable was excluded from
further analyses.
A one-way (Sex) ANOVA failed to reveal any effect of sex, F(1, 14) = 0.95, ns. In general, children performed
very well on this task, averaging 4.2 out of 5 on the postswitch phase (SD = 2.4), significantly above the
chance level of 2.5 out of 5, t(15) = 5.6, p < 0.01. These results remained significant even after excluding
children who failed the preswitch phase (averaging fewer than 4 out of 5 correct; n = 4).