UC Irvine

This thesis covers three experiments related to processing rapid sequences of auditory and visual stimuli. Experiment 1 builds on the discovery that 70% (30%) of listeners perform near chance (perfectly) in classifying rapid sequences of tones (tone-scrambles) as major vs minor. Experiment 1 investigated the relationships between performance in various musical tasks, including the major/minor tone-scramble task. Skill in (1) judging the direction of pitch-change between two successive tones and (2) detecting the presence of an out-of-scale note in a melody were necessary but not sufficient for skill in classifying major vs minor tone-scrambles. These results suggest that skill in classifying major vs minor tone-scrambles requires a cognitive asset beyond those required for the interval-direction and scale-violation tasks. Experiment 2 tested how rhythm and pitch interact to control perceived majorness vs minorness. Participants classified three different types of tone-scrambles as major vs minor. All comprised 15 tones. In one condition, tone-scrambles had no rhythmic variation; in a second condition, every 5th tone was twice as long as the other 12 tones; in a third condition, every 5th tone was as long as a standard tone but was followed by a rest. Rhythmically accentuated tones influenced judgments both more strongly and differently than unaccentuated tones. Moreover, the final tone influenced judgments differently than either standard tones or other rhythmically accentuated tones. Strikingly, when its final tone was a tonic, a tone-scramble was substantially more likely to be judged as "major." Experiment 3 explored how people can use top-down attention to bind information about brightness and loudness. Participants strove to classify rapid streams of disks varying in brightness presented simultaneously with noise-bursts varying in loudness in accordance with different attention instructions. Participants were able to attend to loudness only and ignore variations in brightness, but they had more trouble attending to brightness only and ignoring loudness. The various attention filters achieved by participants demonstrated that top-down attention can powerfully modulate the binding of loudness and brightness in dynamic displays.