"Ratios" and "differences" in perceived sweetness intensity

Abstract

For a number of perceptual continua, it has been shown in previous studies that subjects use only one quantitative comparison between two sensory impressions of a pair of stimuli, irrespective of whether they are instructed to judge "ratios" or "differences". This comparison can be described by algebraic subtraction. The present study was designed to investigate whether this one-operation theory for psychophysical judgment also applied to the sensory continuum of sweetness. Subjects were presented with pairs of fructose solutions, and judged "ratios" of, or "differences" in, perceived sweetness intensities. The pairs were constructed on the basis of a factorial judgment design. The results showed that the reported "differences" could be adequately described by a difference response model, and that the reported "ratios" could be adequately described by a ratio response model. However, the reported "ratios" and reported "differences" were monotonically related, and the marginal means of the log-transformed response matrix of "ratios" were a linear function of the marginal means of the response matrix of "differences". These results are incompatible with the notion that subjects judged differences when instructed to judge "differences", but ratios when instructed to judge "ratios". The consistency of the ratio response model with "ratio" judgments is probably caused by a comparative operation based on "differences" in combination with an exponential response output function. It may be concluded that subjects judge only "differences", and not "ratios", between perceived sweetness intensities. © 1988 Psychonomic Society, Inc.