Cognitive load theory, learning difficulty, and instructional design (Sweller)
Sweller, J. (1994). Cognitive load theory, learning difficulty, and instructional design. Learning and Instruction, 4, 295-312.
Sweller states that the two most important goals of learning are schema acquisition and automation (which can also be interpreted as the storing of automated schemas in long-term memory). In order to encourage the achievement of these goals, it is important to reduce the cognitive load that the instructional task places on the learner. Since intrinsic cognitive load is related to the inherent difficulty of the lesson (i.e., the number of interacting elements), the instructional designer must instead focus on reducing extraneous cognitive load, which is due to the way the lesson is constructed. Sweller mentions several principles that may be used to predict the effects of various instructional features on extraneous load. They include the split-attention effect, the redundancy effect, and the worked example effect. Finally, Sweller reminds the reader that these principles come into play only when the lesson is of sufficiently high complexity. If the overall imposed cognitive load is not high, then the level of extraneous load becomes of little or no consequence.
Schema acquisition and automation are the primary mechanisms of learning. Schema is defined as a “cognitive construct that organizes the elements of information according to the manner with which they will be dealt” (p.296). Schemas provide the basic unit of knowledge. Miller’s “chunks” and Schank and Abelson’s “scripts” may both be considered schema. Knowledge is organized into schemas that affect how new information is addressed. Schemas may be organized around categories such as subject matter and problem solving strategy (i.e., according to solution mode).
Information processing can be either controlled or automatic (Schnieder & Shiffrin, 1977; Shiffrin & Schnieder, 1977; Kotovsky, Hayes & Simon, 1985).
- Controlled processing – when the information needs to be consciously attended to, deliberate thought.
- Automatic processing – occurs without conscious control, when processing occurs automatically without conscious effort allowing attention to be directed elsewhere (compare the act of reading for experienced and beginning readers)
- The process of going from controlled to automatic processing (“automation”) affects everything learned, including schemas themselves.
The function of learning is to store automated schemas in long-term memory. Differential access to a large store of schemas is a critical characteristic of skilled performance. (Research comparing experts and novices (De Groot, 1965; Egan & Schwartz, 1979; Jeffries, Turner, Polson & Atwood, 1981; Sweller & Cooper, 1985). Experts’ schemas permit them to recognize and “chunk” rather than remember or learn.
Schema acquisition and automation also reduce working memory load. Schemas increase the amount of information that can be held in working load by chunking individual elements into a single element. Schemas not only permit long-term storage but also ameliorate working memory limitations. Similarly, automated processing requires less working memory space — thus, automation circumvents limited processing capacity.
Students will often try to solve novel problems through means-end analysis, which involves “attempting to extract differences between each problem state encountered and the goal state and then finding problem solving operators that can be used to reduce or eliminate those differences” (p.299). Students who engage in mean-end analysis may solve the problem but will not achieve schema acquisition and automation (the real purpose of the exercise). Some instructional techniques that may facilitate learning (by reducing extraneous load) include utilizing a goal-free strategy (“Find the value of as many angles as possible”) and worked examples. Another technique involves using partially completed problems that students had to complete themselves.
Split attention effect – instructional materials are assimilated much more rapidly when presented in integrated rather than conventional format with much higher subsequent test performance levels.
Redundancy effect – in the case where the diagram contains all the necessary information (and thus the text is redundant), extraneous cognitive load can be reduced by eliminating the text rather than integrating it with the diagram.
Cognitive load imposed by instructional material can be due to:
- The intrinsic complexity of the core information (instructors have no control; determined largely by element interactivity).
- The cognitive activities required of students because of the manner in which the information is presented (extraneous).
The level of element interactivity refers to the extent to which the elements of a task can be meaningfully learned without having to learn the relations between any other elements. Low – when elements of a task can be learned in isolation; high – when a task cannot be learned without simultaneously learning the connections between a large number of elements.
“A means-ends strategy invariably involves high element interactivity because it requires problem solvers to simultaneously consider the goal, the current problem state, differences between them, problem solving operators and relations between these various entities” (p.309).
What constitutes an “element” depend on the knowledge of the learner as well as the characteristics of the material. “When dealing with high interactivity tasks requiring the learning of multiple elements, we are dealing with schema acquisition. The schemas being acquired may be considered higher or lower level. The elements involved in higher order schema acquisition may be lower level schemas” (p. 305).
If total cognitive load is not excessive due to relatively low intrinsic cognitive load, then a high extraneous cognitive load may not matter. “A high degree of element interactivity may be an essential condition for the generation of the effects associated with cognitive load theory” (p.310).
With material with high element interactivity, failure to assimilate all the elements is interpreted as a failure to understand the concept. With material with low element interactivity, failure to assimilate all the elements is interpreted as a failure to learn or remember (understanding is not invoked).
“…The concept of understanding is only applied to some but not other material. The perspective taken in this paper suggests that information that needs to be “understood,” rather than merely learned, consists of material that has a high degree of element interactivity. Material that has a low level of interactivity only needs to be learned rather than both understood and learned. In this context, understanding can be defined as the learning of high element interactivity material. In fact, it can be suggested that all information falls on a continuum from low to high element interactivity and learning is the only cognitive factor operating. When the schemas associated with high element interactivity material have been acquired, people feel they have understood the material. When the schemas have become automated, it is understood very well” (p.311).