Reevaluation of two models for judgments of perceptual intervals

In Marks and Cain’s (1972) experiment, 12 Ss estimated magnitudes of stimuli presented one at a time and differences in magnitudes of stimuli presented in pairs for heaviness of weight, roughness of emery papers, and area of circles. Their results appeared inconsistent with the two-stage model of magnitude estimation. But the expressions fitted to the data were different from those previously used in tests of the model. An additive constant was omitted. A reanalysis of their data with the constant included yielded support for the model for all three continua. An alternative model proposed by Marks and Cain was reasonably consistent with the da~a for weight, while inconsistent with the data for roughness and area.