Abstract: Recent research has shown that example study only(EE) was more effective(higher test performance) and efficient(attained with less effort invested in learning or test tasks) than example-problem pairs(EP). For problem solving, free recall and problem-solving bring a heavy cognitive load. The process of acquiring knowledge is gradual, and fade example can be used as scaffolding to support the transition from schema acquisition to schema application. And Carpenter et al. (2020) showed that the potential of retrieval practice to promote problem solving depends on how well it enhances the memory of the necessary information needed to solve problems. The necessary information needed to solve the problem may be the key step in the solution step. Therefore, in order to reduce the cognitive load and ensure that the necessary information for solving new problems can be retrieved, this study assumes that retrieving the key steps in problem solving in the learning process can promote the performance of problem solving. Through an experiment, this study investigated the influence of retrieving key steps on problem solving. In the experiment, the complementary method is used to determine the key steps in the example. One hundred and twenty college students participated in the material evaluation. One hundred and twenty college students were randomly assigned to four experimental conditions (lack of worked example from step one or step two or step three or step four). Chi-square test was conducted for the number of people who wrote correctly and the wrong number of people. It is found that the fourth step in the example is the key step to solve the problem. For the formal experiment, eighty-nine college students participated in the experiment. The experiment was designed by single factor (learning strategy: worked example repeated learning group, worked example-problem solving group, worked example-key step retrieved group) between subjects. The results show that the main effect of learning strategies is significant, and the test scores of the worked example-key step retrieved group are significantly higher than those of the worked example repeated learning group and the worked example-problem solving group. There is no significant difference between the worked example repeated learning group and the worked example-problem solving group. For cognitive load, the main effect of learning strategies is not significant. As for the comprehensive index of cognitive load, the main effect of learning strategies is significant. And the cognitive load of worked example repeated learning group is significantly higher than that of worked example-key step retrieved group and worked example-problem solving group. There is no significant difference between the cognitive load of the worked example-key step retrieved group and the worked example-problem solving group. The results of this study have a positive influence on actual instructions. For the study of problem solving, teachers can provide appropriate teaching tips for students in the learning process, that students can retrieve the key steps in problem solving, and help students to effectively promote learning and solve problems.

Key words: retrieval practice, worked example, key step