Objective measures of auditory scene analysis

We describe objective measures of two aspects of auditory scene analysis (ASA). We show that the build-up of auditory streaming can be measured using a behavioural task - detection of a temporal shift of one tone relative to another - that is easiest when the two tones are part of the same stream. This paradigm is used to show that performance can be improved by requiring participants to briefly divert their attention away from the tones, a manipulation that has previously been shown to increase the number of “one stream” judgements in a subjective task. A physiological measure of streaming build-up is also obtained using the mismatch negativity paradigm. In contrast to the strong effects of attention on streaming, we show, using fMRI measures of the brain response to veridical and illusory vowels, that the continuity illusion does not depend strongly on attention.