Faculty Bibliography

It is well known that discrimination response variability increases with stimulus intensity, closely related to Weber's Law. It is also an axiom that sensation magnitude increases with stimulus intensity. Following earlier researchers such as Thurstone, Garner, and Durlach and Braida, we explored a new method of exploiting these relationships to estimate the power function exponent relating sound pressure level to loudness, using the accuracy with which listeners could identify the intensity of pure tones. The log standard deviation of the normally distributed identification errors increases linearly with stimulus range in decibels, and the slope, a, of the regression is proportional to the loudness exponent, n. Interestingly, in a demonstration experiment, the loudness exponent estimated in this way is greater for females than for males

The power function exponent for loudness is traditionally determined by means of a process of magnitude estimation. It is demonstrated in this paper that the exponent can also be obtained by using the procedure of absolute identification of sound intensity. It has been shown that subjects' responses to tones of a given intensity are distributed in a normal distribution whose variance depends on the range, R, over which the tones are distributed. By means of a standard statistical transformation, the normal density in log space is converted to the corresponding probability density in linear space. The power function exponent can then be obtained directly from the linear probability density. We also suggest that there is a direct relationship between the information calculated from experiments on absolute identification of sound intensity and the neurophysiological, poststimulus histogram measured in a nerve fiber in the auditory nerve

This paper considers the information transmitted in absolute judgments as encoded in a stimulus-response matrix (e.g., see Garner and Hake, 1951). When transmitted information is plotted against the number of stimulus categories in the matrix, one obtains a curve that increases monotonically toward a plateau, which is the maximum information transmittable per stimulus for the particular range of stimuli employed. We demonstrate that although the maximum information transmitted is an attribute of the stimulus continuum itself, the shape of the curve is an empirical property of the stimulus-response matrix, which is determined, in part, by maintaining a constant stimulus category width. Therefore, in principle, each curve of information transmitted vs number of stimulus categories can be determined by a single point: the rightmost point on the graph.