THE DEVELOPMENT OF EXECUTIVE FUNCTION IN EARLY ...

does not appear to be the case for 3- to 4-year-olds in the DCCS. Certainly, further investigation is warranted
regarding the question of whether negative priming is a unitary process or whether different mechanisms
underlie negative priming in different tasks and at different ages.
Negative priming has rarely been investigated from a developmental perspective. However, Tipper and
colleagues (1989) have shown that, compared to adults, evidence of negative priming is weak in 7-year-olds in
a Stroop task. How can negative priming play such an important role in the DCCS if it is difficult to observe
even in middle childhood? One possible answer to this question is that the influence of negative priming is
dependent on task complexity; it may be observed first in less complex tasks and later in more complex tasks
(see Tipper & McLaren, 1990; Stuss et al., 1999, for related arguments). Another possibility is that children
failed to exhibit negative priming in previous studies simply because they failed to attend selectively during the
prime phase. Clearly, however, these questions need to be addressed empirically.
Future research might also explore more fully the variables that are related to negative priming on the DCCS
(e.g., see Fox, 1995; May et al., 1995, for reviews). For example, the spatial separation of target and distractor
has been found to be related to the magnitude of negative priming in adults. In order to examine the effect of
spatial separation on negative priming in the DCCS, the Negative Priming version could be administered with
spatially separated stimulus values (analogous to Experiment 6). Similarly, research on negative priming in
adults shows that when more distractors have to be ignored, any single one of them is less strongly inhibited
(Fox, 1995). In the DCCS, the effect of number of distractors could be tested by adding dimensions to the
stimuli. Further, the adult literature on negative priming suggests that negative priming can be long lasting and
persist despite intervening trials (Allport & Wylie, 2000; Fox, 1995). It is unknown whether and under what
circumstances negative priming is persistent in 3- to 4-year-olds in the DCCS. The time course of negative
priming during the preswitch phase is also unknown. We assume that negative priming builds up gradually in
the course of the preswitch. However, it is possible that negative priming reaches maximum strength even after
a single preswitch trial. In order to examine this question, the number of preswitch trials could be manipulated
in the Negative Priming version, as was done in the standard version by Zelazo et al. (1996), who found that 3-
year-old children perseverated after one preswitch trial.
Future studies could also examine the role of negative priming in other measures of executive function, such as
the Wisconsin Card Sorting Test (Chelune & Baer, 1986), the Flexible Item Selection Task ( Jacques & Zelazo,
2001), and the Day-Night-Stroop task (Diamond et al., 2002; Gerstadt et al., 1994). For example, in the Day-
Night Stroop task, children are instructed to say the word "day" when shown a picture of the moon and stars,
and "night" when shown a picture of the sun. Three- to 4-year-old children's difficulties in the Day-Night Stroop
task are commonly attributed to their lack of inhibitory control (Diamond et al., 2002). Specifically, it is argued
that these children have a difficult time inhibiting a word (e.g., "night" when shown the picture of the moon)
that is semantically related to the word they are supposed to say (e.g., "sun"). However, it is also possible that
children have difficulty overcoming the negative priming that occurs when they respond correctly. Using
various measures of executive function should allow researchers to track the development of negative priming
across a wide range of ages. This research could also be extended to include phenomena such as retrievalinduced
forgetting (Anderson & Bell, 2001; Levy & Anderson, 2002), understanding homonyms (Gernsbacher
& Robertson, 1995), and task switching (e.g., Allport & Wylie, 2002).
Finally, it should be noted that this account points to a reconceptualization of the concept of negative priming
and its development. Negative priming is often conceptualized as evidence of an inhibition mechanism that
allows successful selective attention (e.g., Dempster, 1995; Houde & Guichart, 2001; Tipper et al., 1989).
However, the approach outlined here suggests that the suppression of attention resulting in negative priming
may also be a problem to be overcome in the course of development. This characterization contrast sharply with
most inhibition accounts of executive function (e.g., Carlson & Moses, 2001; Kirkham et al., in press; Luria,
1961; Perner et al., 1999; White, 1965). Whereas inhibition accounts suggest that children perform poorly on