This assumption is questioned in the upcoming Advanced Research Techniques Forum. One of the papers, Models of Sequential Evaluation in Best-Worst Choice Tasks, raises serious concerns. The authors present convincing evidence that respondents make sequential choices and that usually the worst alternative is selected first and then the best selected from the remaining alternatives. The conclusion is that we need different best and worst choice parameters, and as a result, Sawtooth's MaxDiff analysis can be misleading. Moreover, the authors note that their findings support the idea of preference construction. That is, pre-existing preferences are not revealed in the choice task, but instead, preferences are created in order to solve the choice task. The paper ends with the following sentence: "We think that it is very important in the model development stage to stop and think about whether the tool that is used to collect data on preferences makes sense and is consistent with anticipated decision processes on actual purchasing decisions."
So we have another reason not to add a MaxDiff package to the R library. However, I do not believe that the paper takes its argument to its logical conclusion. The example from their analysis is a study of hair concerns. They ask respondents to indicate their most and least concern in choice sets of 5 alternatives chosen from the complete list of 15 concerns in all. For example, which of the following items are you the most and least concerned about?
- My hair is coming out more than it used to
- My graying hair is unflattering
- My hair is dry
- I have unruly, unmanageable hair
- My hair is stiff and resistant
Now, if preference were well-formed and established, then perhaps such an unrealistic choice task would still reveal my "true" preferences. But if preferences are constructed in order to solve the choice task at hand, then little that I learn in this study can be generalized to the marketplace. Context and order effects are robust and common in choice modeling because we do not store fully-formed preferences for the thousands of features that we will encounter given all that we purchase over time. Instead, we use the choice task to assist us in the construction of preference for the particular situation in which we find ourselves (situated cognition). Only when the choice tasks mimics the real world can we learn anything of value. Even then, we may have problems because experiments and data collection are always obtrusive.
A previous post, Incorporating Preference Construction into the Choice Modeling Process, provides a more detailed discussion of these issues.
A previous post, Incorporating Preference Construction into the Choice Modeling Process, provides a more detailed discussion of these issues.
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