This dissertation describes three sets of experiments on speech and audition. The first two sets use psychophysical methods to investigate mechanisms of spatial hearing employed by the human auditory system. Results of the first experiments suggest that there is no simultaneous contrast illusion in hearing and that spatial frequency contrast sensitivity functions have a lowpass shape and a low cutoff frequency. The second experiments on increment thresholds for spatially-extended auditory signals suggest that the auditory system is most sensitive to spatially broad signals; a minimum auditory angle experiment using spatially-extended stimuli reproduces established results. As a whole, the results of the first two sets of experiments suggest that auditory mechanisms of spatial hearing lack spatial opponency and have broad receptive fields.

The third experiment investigates whether EEG can be used to discriminate among words imagined by a human subject in the context of imagined sentences. Features identified by a procedure that involves linear discriminant analysis, sequential forward selection and leave-one-out cross validation can be used to discriminate among single words and to discriminate among sentences in which particular words are varied.