dependent aspects of cognitive functioning can have a significant influence on task performance. However, domain-specific aspects (e.g., task strategies and prior knowledge) are as important, if not more so, in children’s learning. Furthermore, considerable evidence supports cognitive load theory (CLT), which argues that the seemingly infinite intellectual capacity of humans is primarily attributable to modifications in long-term memory; short-term memory, at all ages, is tightly constrained to consideration of a maximum of five to seven elements at a time (Sweller and Chandler, 1994). Even well-practiced adults can only process three or four variables simultaneously without compensating for their constraints by some sort of “chunking” or bundling strategy or linear processing (Halford et al., 2005). So, although students’ capabilities almost certainly do improve over the course of their years in K–12, many aspects of real-world engineering design are beyond the cognitive processing limitations even of adults.

Based on their review of the literature, Silk and Schunn came to the same conclusion—that the large number of variables involved in most engineering contexts can easily overwhelm the limited cognitive resources of most individuals, adults or students (Halford et al., 2005; Kuhn, 2007; Kuhn et al., 2000; Schauble et al., 1991). They also found that meta-level knowledge about the nature of causality and the goal of testing can organize their thinking about design. In addition, simplifying tasks by focusing on sub-problems and using external representations (physical and mathematical) are effective strategies that can be taught to students in the K–12 setting. In fact, they found that a number of strategies can help young students overcome memory constraints and lead to mature learning, as well as authentic engineering practice. Research shows that these strategies can be learned in classroom settings.

For example, one strategy is to help students build schemas for analyzing multivariable systems, such as the strategy of assuming additive and consistent effects while controlling independent variables. Although these concepts can be explained at the meta-level, evidence suggests that they can be taught to young children by explicit instruction or experimentation (Keselman, 2003).

“Chunking” is another strategy for overcoming memory constraints. Similar to context-specific schemas, chunking involves creating a mental representation of a situation as a discrete element in memory with many aspects hidden underneath it (Chase and Simon, 1973; Miller, 1956). Another strategy—functional decomposition—is a design-specific strategy that can also be used to simplify a system and focus on one part of it. For example,



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