Trends in Cognitive Sciences
Absolute pitch: perception, coding, and controversies
Introduction
The study of the memory codes used for musical pitch is one of the oldest in experimental psychology, beginning with Helmholtz, Fechner, Stumpf and Wundt. Indeed, the Gestalt psychology movement was launched with the following question: how is it that a melody composed of specific musical pitches retains its identity despite transposition and when none of the original pitches are present? A related question is that of why some people are able to label all the notes of the musical scale as effortlessly as most of us label colors – a phenomenon known as absolute pitch (AP). Recent findings from neuroimaging, psychophysics, developmental psychology and cognitive science are converging to create a critical mass of knowledge on which to build new theories and experiments.
Research on absolute pitch has grown exponentially over the past 120 years. Defined as the ability either to identify the chroma (pitch class) of a tone presented in isolation or to produce a specified pitch without external reference 1, 2, 3, AP occurs in 1 in 10 000 people [2]. People with AP presumably possess an internal template to map musical tones to linguistic labels. Sometimes regarded as a mark of musicianship, AP is in fact largely irrelevant to most musical tasks. Being unable to turn it off, many possessors of AP perform dramatically poorer at judging whether a melody and its transposed counterpart are the same, a task that non-AP musicians accomplish with ease 4, 5.
Comparisons are often made between color labelling in most humans and pitch labelling in AP possessors [2], because AP possessors categorize and label pitches quite effortlessly and automatically. However, the human visual system is constructed in such a way as to allow discrete categories to emerge readily: information about color is separated into three (or sometimes four) streams by cones in the retina [6], and remains separated up to the cortex. By contrast, information from the cochlea and peripheral auditory system is much more continuous and lacks the one-to-one mapping between excitation patterns and percepts [7]. Accordingly, pitch and color perception are phenomenologically different: colors are experienced as belonging to categories; pitches are experienced (by most of us) as continuous. The fact that some individuals place pitches into categories requires an explanation of what is different about these individuals in their development or neural architecture.
Section snippets
Absolute pitch versus relative pitch
AP should not be confused with relative pitch (RP), an ability all trained musicians learn that allows them to identify or produce musical ‘intervals’, or relations between pitches (see Box 1). A trained musician presented with the tones A and C will identify the musical interval as a ‘minor third’ without being able to name either component tone. Told that the first note was an A, she will use her learned knowledge of musical scales to report that the second note was a C. Interestingly, if we
AP: phenomenology
The mental codes used to represent color invoke categories (e.g. red, green, blue). For AP possessors, pitch categories are as fixed and familiar as color categories are for the rest of us, although category width can be idiosyncratic from person to person [10] (Figure 1). When AP possessors hear a familiar piece of music played in the wrong key (either when it is transposed, or when an instrument has been tuned to a different standard), they often become agitated or disturbed. To get a sense
Absolute pitch is not ‘perfect’ pitch
It is important to emphasize that AP possessors do not have an exceptional pitch acuity. Absolute pitch is neither ‘absolute’ nor ‘perfect’ in the ordinary uses of those words; ‘absolute’ refers to judgments established independently, rather than by comparison. The terms ‘absolute’ and ‘perfect’ both imply in the lay mind a level of precision not typically present in AP possessors, who frequently make octave errors (confusing tones that are half or double the frequency), and semitone errors
Origins of AP: phylogeny and ontogeny
Many animals show preferential processing for absolute qualities of stimuli over relational information; it is a cornerstone of learning theory that relational processing requires greater cognitive sophistication. With regard to pitch procesing, rats and wolves have been shown to use AP information, in the latter to identify members of their own pack. Starlings and rhesus monkeys first attempt to solve pitch tasks with AP, and if that fails, can resort to RP as a secondary strategy [22].
Critical periods
Studies suggest that AP is acquired before the age of 9 32, 33, 34, and no case exists of an adult successfully acquiring it [2]. This has led to conjecture that, like grammar and phonology in spoken [35] and signed languages [36], AP must be acquired during a ‘critical period’ or maturational stage before the development of other cognitive skills that might undo it. Indeed, the existence and high incidence of late-acquiring AP possessors among developmentally delayed populations such as
AP: neuroanatomy
AP possessors show neuroanatomical differences and different results on neural tests from non-possessors, especially in working memory and associative memory systems [3], although cause and effect have not yet been teased apart. When listening to transposed tone sequences non-possessors show a mismatched negativity and an attentive P3 evoked response potential (ERP), indicating the activation of working memory 45, 46, whereas AP possessors appear to use long-term memory instead [47]. This is
How is AP acquired?
Controversy exists as to whether AP acquisition requires explicit training 32, 40 or can result merely from incidental exposure to music 38, 60. Most possessors report having acquired the ability without remembering when or how it occurred [32]; all report having had music instruction. The failure to remember the learning episode can be taken as evidence that AP is a form of ‘semantic memory’ but does not necessarily imply that the learning was incidental.
Our own view is that AP is probably
Conclusions
A small percentage of the population has direct access to pitch information in the form of linguistic codes that they can apply to pitches. Research in this area suggests that access to some of this information might exist in a much larger proportion of the population. Infants appear to be born with the capacity to attend to and make use of absolute pitch information in melodic recognition tasks, although general development or musical training causes a strategic shift towards relative pitch
Acknowledgements
The preparation of this report was supported by an FCAR/FQRNT Strategic Professor Award and the Bell Canada Chair in the Psychology of Electronic Communication to DJL, by grants from NSERC (228175–00), SSHRC (410–2003–1255), and VRQ (2201–202) to DJL, and a CIRMMT doctoral fellowship to SER. We thank Giulia de Prophetis, Catherine Guastavino, Hadiya Nedd-Roderique, and Regina Nuzzo for help with the figures. We are grateful to Evan Balaban, Ed Burns, Tina Chin, Caroline Palmer, Gottfried
References (70)
Absolute pitch
Intervals, scales, and tuning
Computational approaches to the development of perceptual expertise
Trends Cogn. Sci.
(2004)Developmental aspects of infant's cry melody and formants
Med. Eng. Phys.
(2002)People with absolute pitch process tones with producing P300
Neurosci. Lett.
(2002)Absolute pitch and planum temporale
Neuroimage
(2001)Functional anatomy of pitch memory: An fMRI study with sparse temporal sampling
Neuroimage
(2003)- et al.
Musical structure is processed in ‘language’ areas of the brain: A possible role for Brodmann Area 47 in temporal coherence
Neuroimage
(2003) Cortical plasticity in an early blind musician: an fMRI study
Magn. Reson. Imaging
(2003)Absolute pitch: An approach for identification of genetic and nongenetic components
Am. J. Hum. Genet.
(1998)