Constrained scaling: The effect of learned psychophysical scales on idiosyncratic response bias

Abstract

We report seven experiments in which subjects were trained to respond with numbers to the loudness of 1000-Hz pure tones according to power functions with exponents of 0.60, 0.30, and 0.90. Subjects were then presented with stimuli from other continua (65-Hzpure tones or 565-nm lights varying in amplitude) and were asked to judge the subjective magnitude of these stimuli on the same numerical scale. Stimuli from the training continuum were presented, with feedback, on every other trial in order to maintain the trained scale. Except for the 0.90 scale, subjects readily learned the predetermined scales and were able to use them to judge the non-training stimuli with group results consistent with those usually reported. Also, in contrast to the usual magnitude estimation results, these results produced extremely low levels of intersubject variability. We argue that such learned scales can be used as "rulers" for measuring perceived magnitudes, according to a common unit.where R is the subjective magnitude of a sensory experience measured by a direct scaling technique (e.g., median or geometric mean magnitude estimation), S is the stimulus magnitude, a is a constant representing the unit of the scale, and m is a constant that varies across sensory con-

Deriving the loudness exponent from categorical judgments

“…In accordance with the results of West et al (2000), we found that the loudness exponent is not necessarily fixed and can vary across subjects. To further determine whether the loudness exponent derived from categorical judgments is, in fact, equivalent to the exponent derived from the magnitude estimation data, one would have to show that the exponent differs significantly at different stimulus frequencies for a given subject.…”

“…The slope of the linear portion of this curve is characteristic of the frequency of the tone studied and varies from above 0.4 for low and high frequencies to approximately 0.3 for tones at 1000 Hz (e.g., Marks, 1974;West, Ward, & Khosla, 2000). We shall show here that the slope of this straight line (the power function exponent) can be obtained from the properties of a stimulus-response matrix constructed from an experiment on absolute identification of sound intensity.…”

The influence of instructions on the adjustment of scales

“…Subjects can, for example, be trained to use experimenter-def ined judgment functions (Baird, Kreindler, & Jones, 1971;West, Ward, & Kosla, 2000). Our study is another case in point, showing that the weighting of successive contexts is governed by instructions.…”

Reversed dimensional analysis in psychophysics

“…Even in psychophysics, such models are subject to criticism (Baird, 1997;Luce & Krumhansl, 1988;Marks, 1974;Marks & Algom, 1998;West, Ward, & Khosla, 2000). Stevens' law, Y 5 CF n , is criticized because of deviations from a power function, as well as high variability in the exponent n due to factors not related to variations in the stimulus F. Anderson (1975Anderson ( , 1992 considered this law to be a conceptual misdirection because of both the use of a simple function across all sensory modalities and the in-capability of handling such aspects of sensation as context and hedonics.…”