Context effects on musical chord categorization: Different forms of top-down feedback in speech and music?

Abstract

A critical issue in perception is the manner in which top-down expectancies guide lower-level perceptual processes. In speech, a common paradigm is to construct continua ranging between two phonetic endpoints and to determine how higher level lexical context influences the perceived boundary. We applied this approach to music, presenting subjects with major/minor triad continua after brief musical contexts. Two experiments yielded results that differed from classic results in speech perception. In speech, context generally expands the category of the expected stimuli. We found the opposite in music: the major/minor boundary shifted toward the expected category, contracting it. Together, these experiments support the hypothesis that musical expectancy can feed back to affect lower-level perceptual processes. However, it may do so in a way that differs fundamentally from what has been seen in other domains.

Figure 1

Score used in each of the four conditions in Experiment 1. Note that within a key (rows), the context sequence was identical, the only difference was in the root of the chord continuum.

Figure 2

Identification results of Experiment 2. A) Percentage of major responses as a function of step and expectancy for major keys. B) The same for minor keys.

Figure 3

Key logistic parameters as a function of expectancy and key in Experiment 1. A) Category Boundary (continuum step). B) Bias (proportion). C) Slope (change in proportion per step).

Figure 4

Harmonic structure of the stimuli in Experiment 1.

Figure 5

Melodic sequences used in Experiment 2.

Figure 6

Identification results of Experiment 2. A) Percentage of major responses as a function of step and expectancy for major keys. B) The same for minor keys. C) Percentage of major responses (grouped across keys) as a function of expectancy.

Figure 7

Key logistic parameters as a function of expectancy and key in Experiment 2. A) Category Boundary (continuum step). B) Bias (proportion). C) Slope (change in proportion per step).

Figure 8

Preliminary major and minor ratings as a function of continuum-step and expectancy for the entire range of stimuli in McMurray et al (in preparation) Panel A: Major Ratings. Panel B: Minor Ratings. Steps corresponding to prototypical major and minor triads are marked with vertical lines.