II. THE PRESCHOOL PROBLEM SOLVING STUDY: SAMPLE, DATA, AND STATISTICAL METHODS

The executive tasks administered to preschoolers varied in stimulus type, presentation format, and response requirements with the goal of sufficiently holding the preschool child's interest within and across tasks to maximize the amount of data that could be collected. Tasks were designed with varying a priori demands on working memory, inhibition, and flexible shifting. Because the end-goal was to model individual variation across the preschool period, the same measures were administered at each time point. The downside of this measurement approach is that performance, even in preschoolers, may be subject to practice effects. Specific efforts, such as changing the colors and shapes of containers used in delay tasks, were implemented to try to minimize carryover across sessions. Tasks also were administered in a fixed order to hold possible carryover effects constant across participants, see Table 1 for the order of administration.