A focus on intraindividual change and person-specific pathways is a necessary starting point for developmental science inquiries. However, research often relies on ergodicity-based assumptions about group averages and other variable-centered approaches. Using ideas associated with relational developmental systems metatheory, such as the Bornstein Specificity Principle, we re-examine the ergodicity assumption using Executive Functioning (EF) data from the Measures and Methods Across the Developmental Continuum Project. Participants from Grades 4 to 12 (M age = 14.60) completed three behavioral EF tasks (i.e., working memory, response inhibition, and cognitive flexibility). The final analytic sample included 64 participants who provided data on 30 measurement occasions. Intraindividual and interindividual EF latent constructs appeared to be different, and we identified a wide range of person-specific EF trajectories. These findings challenge the ergodicity assumption framing variable- and group-oriented approaches to individual development. This study demonstrates the feasibility of collecting intensive longitudinal data to understand youth development on an individual level as an alternative to immediate data aggregation and as means to illuminate the use of the specificity principle in understanding human development and in applications pertinent to enhancing the lives of diverse youth across specific times and places in their specific developmental pathways.

注重个体变化和个人特定的途径是发展科学探究的必要起点。但是，研究通常依赖于基于遍历性的关于组平均值的假设以及其他以变量为中心的方法。使用与关系发展系统元论相关的思想（例如，Bornstein特殊性原理），我们使用跨发展连续性项目的措施和方法中的执行功能（EF）数据重新检查遍历性假设。4至12年级（M年龄= 14.60）完成了三项行为EF任务（即工作记忆，反应抑制和认知灵活性）。最终的分析样本包括64位参与者，他们提供了30个测量场合的数据。个体内和个体间EF潜在构造似乎有所不同，并且我们确定了多种针对个人的EF轨迹。这些发现挑战了以遍历性假设为框架的针对个体发展的变量和群体导向方法。