Eight experiments were performed to investigate factors affecting the discrimination of two characteristics of very brief tones. The subjects (adults with normal hearing) were asked to rate targets that differed either by amplitude envelope or by a change in frequency. For the majority of the trials, a target was followed (after a brief silent interval) by a pure tone referred to as a "mask". Two factors affecting discrimination within this simple paradigm were examined in detail; the frequency separation and the duration of the silent interval between the target and the mask. For most of the other conditions, a target and mask were embedded in a series of sounds that were presented with an isochronous rhythm. Several features of these "background" sounds were varied across the experiments, including their timbre, presentation rate and frequency relationships with the target and mask. / Superior discrimination was obtained when targets were able to perceptually "emerge" from a background of tones or noises. Specifically, performance was strongest when a target was easily segregated from the other sounds in the series by timing factors or through having a unique frequency. Discrimination was also enhanced when the interfering effects of the mask were removed through association with other tones in the sequence. The data suggest that a simple "interruption" model of processing, in which the presence of a mask disrupts subjects' ability to process individual characteristics of a target, does not adequately explain the differences in discrimination observed across the conditions. A more comprehensive explanation could consider attentional factors that may influence subjects' ability to accurately identify which tone in a sequence is to be rated. However, a perspective based on auditory segregation seems to most consistently explain the data; individual characteristics of a target were most easily discriminated when the target was perceived as belonging outside of an auditory group formed by the background sounds. This was especially true when the mask was likely to have been perceived as belonging within the group due to frequency proximity and/or rhythmic regularity.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.35490 |
| Date | January 1998 |
| Creators | Weaver, Lisa L. |
| Contributors | Bregman, Albert (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Psychology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001656231, proquestno: NQ50281, Theses scanned by UMI/ProQuest. |
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