Perceptual constancy of a global spectral property: spectral slope discrimination.

The current study investigated perceptual constancy for spectral slope discrimination when fundamental frequency (F0) and spectral shape were varied across three complex stimuli within a single trial. The three stimulus variables were global or emergent properties of a complex sound. The selection of the stimulus variables was in keeping with notions that perception may be organized in terms of a source-filter model of complex sound production; F0 and spectral slope represent properties of sound sources and spectral shape typically represents a filter property. According to the source-filter model, interaction between stimulus properties should depend upon whether the typical origin of the property was common to the source spectrum or the filter transfer function. The four experiments in the current study demonstrated a significant performance decrement in spectral slope discrimination when F0 (a second source property) varied. However, spectral slope discrimination was minimally altered when spectral shape (a filter property) was varied. The study supported claims that listeners treat source properties as a unit which, in perception, is relatively independent of filter properties.