Human sensitivity to differences in the rate of auditory cue change.

Abstract

This thesis is concerned with auditory motion perception and the combinations of cues that contribute to human sensitivity of signals that change in spatial position. Measurement of how sensitive individuals are to the rates of change for auditory cues are difficult because of confounds between duration, extent, and velocity of the changing signal. Dooley and Moore (1988) proposed a psychometric “tool” for measuring sensitivity to rate of auditory cue change using a duration discrimination task. They reported that duration discrimination was improved when an additional cue based on rate of change (of intensity or frequency) was present. This provided a “back door” approach to measuring sensitivity to rate of change. The current experiments were designed to measure sensitivity to the rate of change in intensity and spatial position. Experiment 1 investigated whether performance was enhanced in a duration discrimination task when additional cues consisting of rate of intensity change (partial replication of Dooley and Moore, 1988), rate of spatial position change, or both cues were provided. Duration discrimination was not enhanced by these cues, in fact, it was worse. Experiment 2 assessed whether duration discrimination could be used to measure sensitivity to rates of changes in intensity and motion if the rate differences were larger. As in Experiment 1, duration discrimination was not improved, and tended to worsen, when the velocity cues were present. Experiment 3 shifted the focus to a direct velocity discrimination task to determine whether sensitivity to rates of spatial change varied with the mix of directional and distance information that specified velocity. Performance was better when both directional and distance cues were provided, compared to conditions where only one of these cues was available. Moreover, the benefit from having both types of information was significantly better when direction and distance cues were weighted to be perceptually equal for each participant.