Selecting an appropriate control group for studying the effects of exercise on cognitive performance.

Differences in expectations between experimental and control groups can influence the outcomes of exercise interventions, emphasizing the need to match expectations across study groups. This online study examined whether the expectations to improve the performance of different cognitive tasks differ between various activities commonly used in research on the effects of exercise and cognitive function. Two hundred and five middle-aged adults performed two reaction-time tasks and one memory task. They were then asked to rate, on a 1-5 Likert scale, their expectations to improve performance in those tasks should they engage in six types of activities for three months: brisk walking, resistance exercise, stretching and balance exercises, watching videos with lectures on art, history, and science, a program of relaxation techniques, and yoga/tai chi/meditation. Results revealed that the highest expectations for improvement were associated with relaxation techniques and yoga/tai chi/meditation. Some activities, such as brisk walking and stretch and balance exercises, shared similar expectations. Previous knowledge of the possible beneficial effects of exercise on cognitive performance also led to higher expectations. To establish causal relationships, researchers should strive to use activities that share similar expectations to improve performance for the experimental and control groups. The findings of this study provide such activity pairs. Finally, researchers should also try to match participants with and without prior knowledge of the benefits of exercise to cognitive function between experimental and control groups.