A series of six studies investigated whether an amodal or modality-specific model of perception best accounted for auditory and visual processing of temporal patterns. Intramodal and intermodal pattern pairs were presented to subjects in a same-different paradigm. The first two studies found that performance on all modality pairs changed in parallel with age and complexity or delay. These data were consistent with the amodal model of perceptual processing: the modality of the patterns did not affect performance. The last four studies found that when considerably more difficult comparisons were combined with blocking on intramodal and intermodal trials a difference emerged between the two types of trials. Intramodal performance was superior to intermodal performance. The effect was subtle though and difficult to isolate. At no point in these studies was there evidence of modality-adeptness; visual and auditory processing of the temporal patterns was equally proficient. A multicoding model was proposed to accommodate these results, in general accord with information processing and amodal models of perception.

The frequency-following response (FFR) is a scalp-recorded evoked potential which faithfully mimics an auditory stimulus waveform. Some research has attempted to relate the FFR to pitch perception based on FFR spectral peaks which correspond to the perceived pitch of the evoking stimulus, but these explanations are not definitive because the pitch of the evoking stimulus is often equal to the waveform envelope frequency or nonlinear distortion products also represented in the FFR. The experiments herein attempt to clarify the relevance of the FFR to pitch perception and as an assay of nonlinear distortion in the auditory system. Using harmonic and inharmonic "missing fundamental" complex tone stimuli, it is demonstrated that: (a) missing fundamental pitch is not represented as a spectral peak in the FFR, (b) the FFR contains energy at the stimulus envelope frequency, primary tone frequencies, and nonlinear distortion product frequencies, and (c) human pitch perception can be predicted by a weighted average of envelope-locked and phase-locked neural activity in the FFR. The origin and properties of nonlinear distortion products measured in the FFR are also investigated.

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Previous research (Scheffers, 1983) has indicated that differences in the fundamental frequencies (F(,0)s) of the two simultaneous components in a vowel mixture facilitate the perceptual separation of the vowels. Experiments 1, 2, and 3 were an extension of that work using simultaneous synthesized vowels. They investigated (a) the effects of using vowels with gliding F(,0)s, and (b) the effects of using crossing versus parallel glides. The results indicated that perceptual separation was better when the mixture contained gliding vowels than when it contained steady state ones. In addition, it was found that the separation effect was even stronger when the glides were crossing as compared to being parallel. Experiment 4 investigated the role of formant peaks in vowel identification by employing a vowel mixed with a simultaneous pulse train masker. It was found that the vowel was better identified when the masker was a gliding pulse train as compared to a steady state one. In Experiments 5, 6, and 7 mixtures of unfiltered and filtered (high- and low-pass) pulse trains were used with steady state and gliding F(,0)s and different F(,0) separations. The results indicated that increased F(,0) differences and the use of glides facilitate the perceptual separation of simultaneous sounds. The superior effect of the crossing glides can be explained in terms of the common frequency modulation of the harmonics in each subset (component of the mixture) and the subsequent decorrelation of the harmonics in the two subsets. The type of filtering used had no apparent effect indicating that separation was possible for high-pass filtered pulse trains, probably based on periodicity (timing) information. These findings were discussed in terms of mechanisms of processing.

Thesis (M.A.)--State University of New York at Binghamton, Psychology Department, 2005. / Includes bibliographical references.

Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 105-106)

Thesis (M. Aud.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 66-68).

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed June 17, 2008). PDF text: xiii, 172 p. : ill. (some col.) ; 2 Mb. UMI publication number: AAT 3294945. Includes bibliographical references. Also available in microfilm and microfiche formats.