Model selection and multiple research goals: The case of rational addiction

A comparison of rational addiction and time inconsistency models of addiction highlights the complexities of model selection when researchers have goals in addition to empirical fit. Although currently the two models of addiction are underdetermined by data, each offers a different understanding of addiction; moreover, the two models offer starkly different policy implications. When the goals of understanding and policy usefulness are added to the goal of empirical fit, a more complex account of model selection is needed. First, the principle of parsimony loses some of its force when researchers also value understanding and policy usefulness. Second, when economists value understanding as well as pure prediction, a broader justification of the realism of assumptions becomes possible. Third, because radically different policy advice flows from these empirically equivalent models, this literature underscores the difficulty of separating the seemingly positive analysis of consumer behavior from normative analysis.