Rationalising Choice with Multi-self Models

This article shows that when multiple selves' preferences are aggregated into a decision, even if the researcher has a fully specified theory of how preferences get aggregated, there are typically no testable implications without restricting the number of selves. This points to the importance of collecting reliable information on the number of selves in interpersonal and intrapersonal decision-making contexts. We establish the result through a linear relationship between the number of selves and the set of choice functions an aggregator is guaranteed to rationalise. The latter relates to a choice function's number of independence of irrelevant alternatives violations, a new measure of irrationality.