A probabilistic model is developed for the pair-comparison
design in which the unfolding principle
that governs the choice process uses a discriminal process
analogous to Thurstone’s Law of Comparative
Judgment. However, this process is governed by the
square of the distance between the location of the person
and the stimulus, rather than controlled by the location
of the stimulus as in Thurstone’s formulation.
A simulation study demonstrates the feasibility of estimation,
and two examples use real data to show the
implications of the unfolding models for psychological
research. Index terms: choice data, item response
theory, pair comparisons, preference data, unfolding.