Towards a model of informational masking: The Simpson-Fitter metric of target-masker separation

Abstract

Informational masking (IM) is the term used to describe masking that appears to have its origin at some central level of the auditory nervous system beyond the cochlea. Supporting a central origin are the two major factors associated with IM: trial-by-trial uncertainty regarding the masker and perceived similarity of target and masker. Here preliminary evidence is provided suggesting these factors exert their influence through a single critical determinant of IM, the stochastic separation of target and masker given by Simpson-Fitter's da [Lutfi et al. (2012). J. Acoust. Soc. Am. 132, EL109-113.]. Target and maskers were alternating sequences of tones or words with frequencies, F0s for words, selected at random on each presentation. The listener's task was to discriminate a frequency-difference in the target tones, identify the target words. Performance in both tasks was found to be constant across conditions in which the mean difference (similarity), variance (uncertainty) or covariance (similarity) of target and masker frequencies or F0s were selected to yield the same value of da. The results are discussed in terms of their implications for the development of a model of IM that emphasizes the statistical properties of signals over loosely defined concepts of masker uncertainty and target-masker similarity. © 2013 Acoustical Society of America.