Dichotomy and perceptual distortions in absolute pitch ability

Abstract

Absolute pitch (AP) is the rare ability to identify the pitch of a tone without the aid of a reference tone. Understanding both the nature and genesis of AP can provide insights into neuroplasticity in the auditory system. We explored factors that may influence the accuracy of pitch perception in AP subjects both during the development of the trait and in later age. We used a Web-based survey and a pitch-labeling test to collect perceptual data from 2,213 individuals, 981 (44%) of whom proved to have extraordinary pitch-naming ability. The bimodal distribution in pitch-naming ability signifies AP as a distinct perceptual trait, with possible implications for its genetic basis. The wealth of these data has allowed us to uncover unsuspected note-naming irregularities suggestive of a "perceptual magnet" centered at the note "A." In addition, we document a gradual decline in pitch-naming accuracy with age, characterized by a perceptual shift in the "sharp" direction. These findings speak both to the process of acquisition of AP and to its stability.

Fig. 1.

Scatter plot of piano tone scores as a function of pure tone scores. Data from 2,213 subjects who completed the survey and acoustical test online are presented. The vertical gray line indicates the cutoff value of 24.5 for our operational definition of AP1, as defined in ref. . The dashed diagonal line indicates a theoretical 1:1 correlation between pure and piano tone responses. The gray box indicates the range of scores expected by chance distribution, with mean expected score by chance of 7.125 and with 95% of expected values lying between scores of 3.25 and 11.75. The area of the circle for each data point is proportional to the number of individuals scoring at that point.

Fig. 2.

Visual representation of pure and piano tone deviations as a function of age and of pitch frequency. Flat (negative) and sharp (positive) deviations are color-coded, as indicated in the key, with a value of 0.5 per semitone deviation from the correct response (0 deviation, coded green). Errors of greater than three semitones in either direction are coded gray, and failure to assign a tone within 3 seconds is coded black. Data are summarized for 981 subjects, with an age range of 8–70, who tested AP1. Frequencies are arranged in ascending order from left to right. Scored pure tone frequencies range from D#2 to B7 (77.78–3,951.10 Hz), and piano tone frequencies range from C#2 to A7 (69.30–3,520.00 Hz). Black and gray arrowheads indicate G#'s in pure and piano tone tests, respectively.

Fig. 3.

Pitch perception as a function of age for pure (A–C) and piano (D–F) tones. (A and D) The number of correct pure (A) and piano (D) tone responses plotted as a function of age for the 981 AP1 subjects. Some data are obscured by superimposition of data points. The lines represent the regression, in which Pearson correlation coefficients are −0.251 (with a 95% confidence interval of −0.309 to −0.192, P < 0.0001) and −0.244 (95% confidence interval of −0.302 to −0.184, P < 0.0001) for pure and piano tones, respectively. (B and E) The decline in pitch-naming ability can be visualized. The mean correct responses by age clusters are summarized as follows: 8–19 (n = 319), 20–29 (n = 374), 30–39 (n = 130), 40–49 (n = 100), 50–59 (n = 45), and 60–70 (n = 13). (C and F) The data for the algebraic means of the deviations for all responses within each age group (as above), where a correct response is assigned a value of 0 (no deviation), semitone sharp and flat errors are assigned values of +0.5 and −0.5, respectively, whole tone sharp and flat errors are assigned values of +1.0 and −1.0, respectively, etc. The tritone, which was rarely assigned, was given the value of +3. Unnamed pitches were discarded, and, in calculating the mean, the denominator was decreased from 36 by the number of discarded notes. Error bars indicate SEM.

Fig. 4.

Pitch deviation as a function of pitch chroma. The mean deviations (A) and mean absolute deviations (B) in pitch identification (as calculated in Fig. 3) are plotted for each pitch. The distribution of pitches is given in Materials and Methods.

Fig. 5.

Relationship between nonresponses and correctly identified responses for each pitch chroma. Plotted are percentages of pitch cues unanswered as a function of percentages of pitch cues correctly identified for each pitch class. Data are compiled from responses from 981 AP1 subjects.