Meter, a hierarchical mental organization used to group temporal patterns of sound, presents a unique opportunity to study the dynamic cognitive structuring of auditory perception. Often discussed in alternating cycles of phenomenally strong and weak beats, meter appears to guide our attention to expected points in time. Here, we examine the possibility that improved auditory perception occurs at moments when events are most strongly anticipated, and also examine the effect of long-term training and experience that may covary with metric expectations.
Eleven recruited subjects (six musicians and five non-musicians) participated in a two part study. A preliminary study asked listeners to discriminate timing distances between brief pairs of click pulses. The study used an adaptive procedure to determine a stimulus level distance where performance was standardized across participants. Generally, performance rates for all subjects were consistent.
Each participant’s timing distance was used in the main study, where listeners heard equally-spaced sequences click pulses—one of which was temporally reversed in order. While imposing different metric organizations (i.e., hearing clicks groups of two or three), participants were to identify the metric position in which the click pulse was reversed temporally. During this procedure, the electroencephalogram was recorded from participants’ scalps.
Behavioral results indicate that musicians did not perform better than non-musicians at the task, a surprising finding suggesting that long-term training does not affect top-down influence on temporal acuity. Another surprising finding is that the context of click pulses, which can be presented in normal or reversed order, had effects on judgment. Consistent with predictions, conditions with metric groups of three yielded a worse performance overall, suggesting ternary organization of sounds is a more difficult metric hierarchy to maintain. Finally, beat-based differences arose only in comparing weak beats of one metric condition to all other beats; although there was a main effect of reporting metric positions that temporal reversals occurred, support for the notion of beat-based differences that underlie varied levels of attentional focus is spurious.
In analyzing neural signals, preliminary analysis suggests that mentally-maintained meter that is imposed upon sequences with identical stimuli may be observable in the electroencephalogram. However, differences in musician neural responses appear to be highly individualized, and perhaps not observable in non-musicians. However, a comparison of strong and weak beats in neural waveforms for all participants does not show significant differences; thus, evidence for mental representation for meter cannot be reported.
Findings from the study are implicated in understanding the neural mechanics of perceiving and organizing large acoustic structures such as speech and music.