Abstract
Two experiments used subjective and objective measures to study the automaticity and primacy of auditory streaming. Listeners heard sequences of “ABA–” triplets, where “A” and “B” were tones of different frequencies and “–” was a silent gap. Segregation was more frequently reported, and rhythmically deviant triplets less well detected, for a greater between-tone frequency separation and later in the sequence. In Experiment 1, performing a competing auditory task for the first part of the sequence led to a reduction in subsequent streaming compared to when the tones were attended throughout. This is consistent with focused attention promoting streaming, and/or with attention switches resetting it. However, the proportion of segregated reports increased more rapidly following a switch than at the start of a sequence, indicating that some streaming occurred automatically. Modeling ruled out a simple “covert attention” account of this finding. Experiment 2 required listeners to perform subjective and objective tasks concurrently. It revealed superior performance during integrated compared to segregated reports, beyond that explained by the codependence of the two measures on stimulus parameters. We argue that listeners have limited access to low-level stimulus representations once perceptual organization has occurred, and that subjective and objective streaming measures partly index the same processes.
Highlights
We present a brief review of the literature as it pertains to the automaticity and primacy of auditory streaming, followed by two experiments that combined percept reports and a performance-based measure with a simple model
Late deviants were better detected in the switch condition than the attend condition, main effect of task on d=, F(1, 11) ϭ 6.17, p ϭ .030, p2ϭ .36; no interaction with ⌬f, F(1, 11) ϭ 1.33, p ϭ .274, p2 ϭ .11, indicating that the removal of attention from the tones during the first part of the sequence, or the switch of attention itself, improved performance compared to the late attend condition in which the tones were attended throughout
That partial resetting in the proportion of segregated reports over trials and participants reflects two phenomena: first, that the immediate percept following a silent gap or switch of attention is likely to be of integration; second, that the prevalence of streaming prior to the interruption or change of attentional focus has a bearing on the subsequent perceptual dynamics
Summary
Twelve naïve listeners (five males, age range 20 –31 years, mean age ϭ 24.5 years) with normal hearing (average pure tone threshold Ͻ20 dB HL for 500 –3,000 Hz, the frequency range spanned by the stimuli) were recruited from the Medical Research Council Cognition and Brain Sciences Unit participant panel and paid for their time. In occasional “deviant” triplets the B tone occurred 50 ms later than in the standards. These parameters were chosen to match conditions in Carlyon et al (2001), Cusack et al (2004), and Thompson et al (2011), and were anticipated to generate intermediate levels of streaming for maximal sensitivity of both measures to the attention manipulation. The eight combinations of deviant position (none; early only; middle only; late only; early and middle; early and late; middle and late; early, middle, and late) were represented across sequences
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