grades (Siegler, 1998). Instead, there are many twists and turns and misconceptions that develop along the way. In fact, growth can be difficult to gauge, as it sometime follows a U-shaped pattern, with apparent regressions or intermediate constructions developing as part of the process. In this context, misconceptions or wrong ideas are not necessarily a bad thing, nor are they necessarily a sign of a deeply held systematic alternative theory—some are highly context dependent and even quite transitory. However, they do reflect deeper conceptual difficulties, and understanding the reasons for those difficulties can be instructive. In some cases, misconceptions develop in part because of limited symbolic tools available to students or limitations in conceptual knowledge in other domains (e.g., having mathematics based on natural rather than rational number, having limitations in geometric understandings).

Some misconceptions may stem from alternative ontological commitments that constrain children’s ideas. If children assume that an entity or relation belongs to a fundamentally different kind of thing, that assumption can derail attempts to link up their conceptual system with that of adults or older children. For example, if fire is thought of as a kind of stuff rather than a symptom of an event (combustion), that misattribution of fire to the wrong category (a substance instead of an event) can lead to dramatically different inferences about other properties of fires. More broadly, conceptual change may be more difficult when the child’s naïve conception assigns entities in a domain to a different ontological category than an adult’s conception assigns them (Chi, 2005). In contrast, if a young child initially misconceives an entity as a different sort of thing but in the same ontological category, then conceptual change may be much easier to achieve (Chi, 2005). For example, a child might initially think that germs are like small insects inside the body instead of knowing that they are a different kind of organism, but such a mistake makes the same ontological commitments and would be relatively easy for a child to surmount.

Multiple factors contribute to the changes described in this section. Thus, we need to avoid the trap of looking for a single explanation for such diverse phenomena. Instead, we need to identify the range of important factors and explore how they contribute and interact with one another. Many of these factors may be primarily experiential in nature (rather than maturational in a strict biological sense), and there are a variety of ways that experience can contribute to growth. Even in the case of more maturationally based factors (such as increases in working memory, processing speed, capacity for attention, self-regulation, executive function), there is evidence for interactions with experiential factors in these developments as well. For example, many factors (knowledge, processing speed, strategies) affect measured short-term storage span of memory, and, although measured short-term storage span increases with age, many argue that short-term storage



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