Comparative judgments with numerical reference points

Abstract

A model of subjective magnitude comparisons is explored, which assumes that subjects compare symbolic stimulus magnitudes with respect to a reference point. The reference point may be established implicitly by the question (e.g., "Which is larger?" vs "Which is smaller?") or be presented explicitly (e.g., "Choose the stimulus closer to X."). The model was tested in five experiments in which subjects judged which of two comparison digits was closer to (or further from) a reference digit. Regression analyses in three experiments revealed that reaction time depended on the ratio of the distances from the comparison items to the reference point. The other two experiments provided evidence that subjects can strategically vary the processes by which they compare stimuli to a reference point. The results indicated that subjects can perform various types of "analog arithmetic" using either the linear number scale or a nonlinear scale of subjective digit magnitude.