In a choice between any two options, decision makers can be divided into three segments: those who strongly prefer the first option, those who strongly prefer the second option, and those who might choose either option depending on the particular conditions (switchers). In any reference state, such as the experimental control, most switchers are likely to favor one of the two options. Thus, the growth potential of the option favored by switchers in the reference state creates effect propensity in the opposite direction, whereby any condition or manipulation applied to the reference state is more likely to increase the share of the other option. We test this proposition in a series of studies in the context of choices between action (e.g., a gamble or a higher-price/quality) and inaction (e.g., a sure gain or a lower-price/quality) alternatives. The results indicate that a large majority of conceptually unrelated manipulations tend to increase the choice share of action alternatives. This effect propensity can be reversed when the action alternative is the status quo option in the reference (control) state. We discuss the implications of effect propensity for the interpretation of research findings and theory tests.
