Cognitive load in percentage change problems : unitary, pictorial, and equation approaches to instruction

Eighth grade students in Australia (N = 60) participated in an experiment on learning how to solve percentage change problems in a regular classroom in three conditions: unitary, pictorial, and equation approaches. The procedure involved a pre-test, an acquisition phase, and a post-test. The main goal was to test the relative merits of the three approaches from a cognitive load perspective. Experimental results indicated superior performance of the equation approach over the unitary or pictorial approach especially for the complex tasks. The unitary approach required students not only to process the interaction between numerous elements within and across solution steps, but also to search for critical information, thus imposing high cognitive load. The pictorial approach did not provide a consistent approach to tackling various percentage change problems. Coupled with the need to coordinate multiple elements within and across solution steps, and the need to search for relevant information in the diagram, this approach imposed high cognitive load. By treating the prior knowledge of percentage quantity as a single unit, the equation approach required students to process two elements only. Empirical evidence and theoretical support favor the equation approach as an instructional method for learning how to solve percentage change problems for eighth graders.