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Publication Detail
Effect of temporal regularity on segregation
  • Publication Type:
    Conference
  • Authors:
    Andreou LV, Chait M
  • Publication date:
    2010
  • Name of conference:
    British Society for Audiology
  • Conference start date:
    01/01/2010
Abstract
The idea that predictive modelling and extraction of regularities plays a pivotal role in the formation of auditory objects has recently attracted considerable attention (Denham & Winkler, 2006). The present study investigates the effect of one basic form of regularity, temporal regularity, on auditory stream segregation. Towards this goal, we departed from the classic auditory streaming paradigm and created a stimulus consisting of temporally independent streams of A and B tones, each with an inter-stimulus interval (ISI) between 100-400 ms (allowing for temporal overlaps between streams). Stimuli were presented in ~1 min trials. Three types of amplitude modulations (AMs) were applied randomly to tones within the streams. Listeners were instructed to attend to one stream and detect a particular sequence of AMs (AM0-AM1-AM2), which occurred about 5 times per trial. In Experiment 1, we confirmed that this task is a suitable objective measure of segregation by measuring performance in 3 conditions: (1) A single stream of either A or B tones (2) A combined presentation with frequency spacing of 11 semi tones (s.t.) (3) A combined presentation with spacing of 4 s.t. Results indicated that, as expected, performance decreases significantly with decreasing frequency separation. In Experiment 2, we investigated the effect of regularity by instructing listeners to attend to one of the streams which was always temporally random, while modulating the properties of the competing stream in 4 ways: (1) random ISI between 100-400 ms, (2) temporally regular, ISI= 400 ms, (3) regular, ISI= 250 ms, and (4) regular, ISI= 100 ms. For a frequency separation of 4 s.t., performance in condition 1 did not differ from conditions 2, 3 and 4 (average dā€™= 2.4). However, for a separation of 2 s.t. we found strong effects of regularity such that performance on conditions 3 and 4 (dā€™= 2.1) was significantly improved relative to condition 1 (dā€™= 1.7). Namely, modulating the regularity status of the competing stream resulted in appreciably improved performance, presumably by helping listeners perceptually segregate the interfering regular stream away from the attended sequence. Contrary to previous studies employing subjective tasks (French-St. George & Bregman, 1989), our results demonstrate that, at least under certain conditions, temporal regularity does affect separation and provide support for models of stream segregation that involve segregation based on the formation of predictive models.
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