THE DEVELOPMENT OF EXECUTIVE FUNCTION IN EARLY ...

3. When the rules did not span major branches, however, even 3- to 4-year-olds were able to treat the same
stimulus in two different ways. That is, under these circumstances, 3- to 4year-olds effectively redescribed the
test card and inhibited their old way of responding.
The third experiment in Study 2 (i.e., Experiment 6) replicated these findings in a single test, while also
assessing whether the separated stimuli used in the unidimensional version in Experiment 5 might have
accounted for children's success. According to Shepp and Barrett (1991), as well as work with adults (see
MacLeod, 1991), the use of spatially separated stimuli may facilitate analysis of the stimuli into dimensions or
attributes. The findings from Experiment 6, however, clearly indicate that conflict among rules, but not spatial
separation of the stimuli, determines performance on the DCCS.
Taken together, the results of Study 2 show that conflict among rules is a key determinant of difficulty, but that
conflict interacts with dimensionality.
Perseveration is, therefore, at least partly a function of rule complexity, and cannot be attributed to a general
problem with inhibitory control—either at the level of responses or at the level of representations. Similarly,
it cannot be explained by a general difficulty redescribing stimuli. The redescription hypothesis cannot
account for the finding in Experiment 6 that children performed significantly better on the Unidimensional
Separated version than they did on the Bidimensional Separated version. These two versions should be
equally likely to alert children to the need to redescribe the test cards. From the perspective of CCC theory,
however, a difference between these versions would be expected because only the Bidimensional Separated
version
requires children to use rules nested under different major branches of the tree structure in Figure 3. CCC theory
holds that 3- to 4-year-olds fail to resolve conflict at a particular level of complexity at the level of specific
rules—because they have difficulty formulating a higher order rule for selecting between dimensions.
Study 3 examined further what types of conflict in typical executive function problems pose difficulties for 3- to
4-year-olds by asking whether children who perseverate on the DCCS perseverate on specific rules as opposed
to dimensions per se or particular stimuli. Although children perseverated on the Partial Change version (in
which the values of the dimension that was relevant on the preswitch phase were retained during the postswitch
phase), they performed well when the values of both dimensions were changed (Total Change version). These
findings suggest that children perseverate on specific rules (e.g., "If red, then there"), consistent with CCC
theory, according to which the selection and use of preswitch rules increases the activation level of those rules
(Marcovitch & Zelazo, 2000) .
Study 4 was designed to replicate Study 3 and also to examine the possible role of negative priming on the
DCCS in relation to other possible sources of difficulty. In the Negative Priming version of the DCCS, the
values of the dimension that was relevant during the preswitch phase were removed during the postswitch
phase. Results indicated that this version was as difficult as the standard version, as would be predicted if the
competing rules are negatively primed and thus inhibited during the preswitch phase. Further work suggested
that negative priming depends on the active selection of one pair of rules against a competing alternative. In
Experiment 9, children performed well on the Negative Priming (redundant preswitch) version, in which test
cards were identical to the target cards during the preswitch phase so children did not need actively to select
against competing rules. Children also performed well in the Redundant version, suggesting that persistent
activation may also depend on attending selectively to the preswitch rules.
IMPLICATIONS FOR ALTERNATIVE ACCOUNTS OF THE DEVELOPMENT OF EXECUTIVE
FUNCTION
Memory Accounts
Several influential accounts of development during the preschool years suggest that age-related changes in
executive function will be limited by the development of children's memory (e.g., Case, 1992, 1995; Gordon &
Olson, 1998; Olson, 1991; Pascual-Leone, 1970). It is possible that the growth of memory, perhaps particularly
working memory, constrains the number of rules that children can use in the DCCS. For example, 3-year-old