Spatial uncertainty and proximity effects in informational masking identically related to the Simpson-Fitter metric of target-masker separation

Further evidence is provided suggesting a primary dependence of informational masking (IM) on the stochastic separation of target and masker given by Simpson-Fitter's da [Lutfi et al. (2012). J. Acoust. Soc. Am. 132, EL109-113.]. The stimuli were brief bursts of Gaussian noise or words played in sequence as masker-target-masker triads. The apparent position of bursts (words) from left to right was varied independently and at random on each presentation using KEMAR HTRFs. In the 2IFC procedure the listener's task was to choose the target positioned further to the right. Spatial uncertainty of the masker was increased by increasing the position variance of the masker. Spatial proximity of target to masker was increased by decreasing the position mean-difference between target and masker. Performance in both cases was well described by a single linear function relating d' to da; intercepts differed across listeners, but slopes were similar. Comparable results presented at this meeting for the effects of spectral uncertainty and similarity of target and masker suggest that the statistical properties of signals may be a more significant determinant of IM than their specific acoustic properties.