BINAURAL SUMMATION AFTER LEARNING PSYCHOPHYSICAL FUNCTIONS FOR LOUDNESS

Do response-related processes affect perceptual processes? Sometimes t hey may: Algom and Marks (1990) produced different loudness exponents by manipulating stimulus range, and thereby also modified the rules of loudness summation determined by magnitude scaling. The present study manipulated exponents by having a dozen subjects learn prescribed pow er functions with exponents of 0.3, 0.6, or 1.2 (re sound pressure). S ubjects gave magnitude estimates of the loudness of binaural signals d uring training, and of monaural and binaural signals after training. D uring training, subjects' responses followed the nominal functions rea sonably well. Immediately following training, subjects applied the num eric response scales uniformly to binaural and monaural signals alike; the implicit monaural-binaural loudness matches, and thus the basic r ules underlying binaural summation, were unaffected by the exponent le arned. Comparison of these results with those of Algom and Marks leads us to conclude that changing stimulus range likely influences underly ing perceptual events, whereas ''calibrating'' a loudness scale throug h pretraining leaves the perceptual processes unaffected.