Academic journal article Attention, Perception and Psychophysics

Pitch Chroma Discrimination, Generalization, and Transfer Tests of Octave Equivalence in Humans

Academic journal article Attention, Perception and Psychophysics

Pitch Chroma Discrimination, Generalization, and Transfer Tests of Octave Equivalence in Humans

Article excerpt

Published online: 25 September 2012

© Psychonomic Society, Inc. 2012

Abstract Octave equivalence occurs when notes separated by an octave (a doubling in frequency) are judged as being perceptually similar. Considerable evidence points to the importance of the octave in music and speech. Yet, experimental demonstration of octave equivalence has been problematic. Using go/no-go operant discrimination and generalization, we studied octave equivalence in humans. In Experiment 1, we found that a procedure that failed to show octave equivalence in European starlings also failed in humans. In Experiment 2, we modified the procedure to control for the effects of pitch height perception by training participants in Octave 4 and testing in Octave 5. We found that the pattern of responding developed by discrimination training in Octave 4 generalized to Octave 5. We replicated and extended our findings in Experiment 3 by adding a transfer phase: Participants were trained with either the same or a reversed pattern of rewards in Octave 5. Participants transferred easily to the same pattern of reward in Octave 5 but struggled to learn the reversed pattern. We provided minimal instruction, presented no ordered sequences of notes, and used only sine-wave tones, but participants nonetheless constructed pitch chroma information from randomly ordered sequences of notes. Training in music weakly hindered octave generalization but moderately facilitated both positive and negative transfer.

Keywords Octave equivalence . Octave generalization . Note-range discrimination . Music training . Psychoacoustics . Music cognition . Sound recognition

Two acoustic events are separated by an octave when the frequency of the second event is double or half the frequency of the first. This logarithmic relationship between acoustic events spaced an octave apart is a description of the physics of wave transmission. Human perception has evolved to grasp this unique acoustic relationship in speech and music (see, e.g., Burns, 1999; Patel, 2003; Peter, Stoel-Gammon, & Kim, 2008). In all cultures, the production and perception of octaves are fundamental characteristics of music (Crickmore, 2003). That is, although the number of notes in an octave, their labels, and their frequencies can differ in music across cultures, all cultures recognize the similarity between notes an octave apart (the notes are said to have the same pitch chroma); this phenomenon is known as octave equivalence.

Octave equivalence is one of the two most potent determinants of pitch judgments. A second important determinant is pitch height, which is a log-linear scale of pitch in which the more two sounds differ in frequency, the more they differ in pitch. Octave equivalence and pitch height are opposing percepts. For example, a note one-third of the way between two notes separated by an octave is more similar in pitch height to the first note than to the second, whereas the two notes separated by an octave are more similar to one another in chroma than to the note one-third of the way between them.

Perception of octave equivalence has a neural basis: For example, neurons in the auditory midbrain show preferences for harmonically related sounds, and the ventral nucleus of the lateral lemniscus has a structure reminiscent of the pitch helix (Langner & Ochse, 2006). The pitch helix is a spiraling structure that completes a circular motion once in each octave. The helix was first proposed as a theoretical spatial mapping of human pitch height and chroma perception by MoritzWilhelm Drobisch (ca 1846), then used by Shepard (1982) much later in his well-known theory of pitch perception.

Despite all of the evidence and theory supporting the importance of octaves, experimental demonstration of the perception of octave equivalence has been problematic. In the identification of simple melodies, alteration of the octaves of several of the notes reduces identification of the melodies (Deutsch, 1972). …

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