Explain how expectancy effects are problematic in studies testing the effects of exercise on psychological states

Question

What will be an ideal response?

Answer 1

Expectancy effects is one of the methodological issues that investigators face when testing the effects of exercise on psychological states. If participants in an exercise group are given more attention than subjects in other conditions, such as a wait list control condition (i.e., placement on a waiting list for treatment), then will the exercisers show elevations in mood because of their positive expectations and the attention they receive from staff or because of the effects of exercise itself? How can we best differentiate exercise effects from expectancy effects?

Even comparing exercise to an effective anti-depressant medication can be problematic since differences between an effective medication and an equally effective exercise protocol are not expected to be statistically significant. Without a control group for expectancy factors we cannot rule out the expectancy effect's contribution to the outcome for either treatment group. Therefore, we need an adequate prospective design with good experimental controls to determine the efficacy of exercise on these psychological states and conditions. These studies are less common because using more complex and tightly controlled research designs is more costly and labor intensive for researchers.