Effects of stimulus context on magnitude estimations and category ratings of perceived loudness--the spacing of intensity intervals

Effects of stimulus context on magnitude estimations and on category ratings were examined for a range of stimulus intensities of a 1-kHz tone. The stimuli were distributed in equal-interval steps of energy so they formed a perceptual cluster of high-intensity tones with a perceptual outlier at the lowest intensity. According to the Invariance Principle, the shape of the response function should not be affected by the distribution of stimulus intensities. However, neither magnitude estimations nor category ratings yielded the linear functions predicted from the Invariance Principle when plotted on log-log axes. Instead, both procedures yielded concave-upward response functions for the group data as well as for the individual data sets of the six subjects. Moreover, unlike previous reports of a nonlinear relationship, we found a linear relationship between magnitude estimations and category ratings. Rather than implying an equivalence of the underlying sensory scales, however, our results may imply subjects used a similar attention strategy for both procedures. We consider some theoretical suggestions, including an attention-band concept, for modification of a multistage stimulus-response (S-R) transformation model.