“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 ofthe 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.

Test of the Ratio Judgment Hypothesis

“…If we can discriminate ratios from differences, we must be capable of producing these two orders in terms of judged ratios and of judged differences. However, it has been found that the order of A, B, and C obtained in terms of judged ratios and that obtained in terms of judged differences are the same order (Birnbaum & Elmasian, 1977;De Graaf & Frijters, 1988;Mellers, Davis, & Birnbaum, 1984;Parker & Schneider, 1974;Schneider, Parker, Farrell, & Kanow, 1976). This finding shows that people are incapable of distinguishing intensity ratios from intensity differences.…”

Labeled Magnitude Scales: A critical review

“…For continua that do not contain a natural, well-defined zero point, such as taste and smell intensity, ratios cannot be calculated. Therefore, a 'difference' operation is most logical (De Graaf & Frijters, 1988;Schifferstein, 1995). On the other hand, for continua with a clearly defined zero point, such as line length and area size, a 'ratio' operation may be more plausible (Schneider & Bissett, 1988).…”

Two operations for "ratios" and "differences" of distances on the mental map.

“…For a variety of continua, judgments of “ratios” and “differences” of subjective magnitudes appear to be monotonically related (Birnbaum, 1978, 1980, 1982; Birnbaum & Elmasian, 1977; Birnbaum & Veit, 1974; De Graaf & Frijters, 1988; Elmasian & Birnbaum, 1984; Hardin & Birnbaum, in press; Schneider, 1982; Schneider, Parker, & Upenieks, 1982; Veit, 1978, 1980). Because actual ratios and differences would not be expected to be monotonically related in the factorial designs used in this research (Krantz, Luce, Suppes, & Tversky, 1971; Miyamoto, 1983), such experiments provide nontrivial tests of Torgerson's (1961) hypothesis that subjects perceive or appreciate but a single relation between a pair of stimuli, despite instructions to judge “ratios” or “differences.” 1…”