Robert H. Gilkey, Ph.D. (Advisor); Brian D. Simpson, Ph.D. (Committee Member); Scott N.J. Watamaniuk, Ph.D. (Committee Member)
Master of Science (MS)
The effect of masker spatial variability and masker fringe on the perception of a brief tone in noise was investigated in a detection task. Simpson (2011) found large effects of spatial variability (randomizing masker locations from trial to trial) in a masked localization experiment, as well as two effects of masker fringe (masking noise before the onset of the target): 1) cuing the masker location (spatial cuing effect) and 2) temporally separating the onset of the masker and the onset of the target (onset effect). In contrast, in detection studies, the effects of masker spatial variability are small (e.g., Bernstein & Trahiotis, 1997) and the possibility of a spatial cuing effect has not been directly examined. However, onset effects of similar magnitude to those observed by Simpson have been reported (e.g., McFadden, 1966). To determine whether these differences in the effect of masker variability between localization and detection could be attributed to the fact that in localization experiments there is also trial-to-trial variability in the target, we conducted a detection experiment via headphones using a 2 Masker Variability (variable & fixed) x 2 Target Variability (variable & fixed) x 2 Masker Fringe (no fringe & fringe) factorial design. We used a 60-ms, 500-Hz sinusoidal target and a 60-ms Gaussian noise masker (and a 500-ms Gaussian noise masker fringe in the fringe conditions). Masker and/or target location was varied laterally by varying the interaural time difference (ITD) of the fine structure. We found little effect of masker variability, in agreement with previous detection studies, and the presence or absence of target spatial variability did not alter the pattern of results. Because the effect of masker variability was small, there was limited opportunity to observe a spatial cuing effect, but there was an onset effect of fringe that was of similar magnitude to that observed in previous detection studies. In the binaural detection literature, the onset effect is large under dichotic conditions than dichotic conditions. Similarly, the onset effect we observed varied significantly with the spatial separation between the target and the masker, being small when the target and masker were collocated and large when they were widely separated. Various explanations for the results were considered. Spatial transition appears to be a reasonable explanation for the detection results, but not for localization; and segregation appears to be a reasonable explanation for the localization results, but not for detection. Although the data in the literature on the overshoot effect are somewhat inconsistent, it seems possible that overshoot could be used to explain both sets of data.
Department or Program
Department of Psychology
Year Degree Awarded
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