Wednesday, February 15, 2012

Daniel J. Levitin, This is Your Brain on Music (2007)

A debate has raged over the past fifteen years as to whether music is an adaptation, a trait that emerged as a result of an evolutionary process. Several well-known psychologists and neuroscientists have weighed in on this subject including Steven Pinker, Daniel J. Levitin, and Pascal Boyer. Pinker, on the one hand, has dismissed music as "auditory cheesecake," while Levitin is convinced that music is an adaptation. Neither, in my view, is precisely correct. In the parlance of evolution, an adaptation is a trait that has a functional role in the life of an organism that evolved and is maintained as a result of natural selection. What we typically think of as music --- a song, with or without words --- is not an adaptation; it is not a trait. As is the case with language and learning, it is our capacity for appreciating, learning, creating, and performing music that is the trait. That capacity has a functional role in the life of an organism.

In How the Mind Works, Steven Pinker referred to music as "auditory cheesecake." It confers no survival advantage, he asserts, but music is merely a "confection crafted to tickle the sensitive spots of at least six of our mental faculties." Music, says Pinker, is a "technology [or a "spandrel" as Stephen Jay Gould might have said], not an adaptation." With music, humans merely exploit the language and communication system that evolved through survival and sexual selection pressures.

Levitin, a former musician and sound specialist turned neuroscientist at McGill University, explains that he "took notice" when Pinker called music "auditory cheesecake" and described music as "useless" as far as biological cause and effect are concerned. In contrast, Pinker puts language, vision, and social reasoning in the category of adaptations that have survival value for the human species. "Music could disappear tomorrow," Pinker says, and our "lifestyle would be virtually unchanged." The musician in Levitin was clearly professionally enraged. So he wrote a book on the subject, This is Your Brain on Music. The final chapter of this book, where Levitin challenges Pinker's views, is titled "The Music Instinct," borrowing a phrase from an earlier Pinker book titled The Language Instinct.

By "instinct," Pinker means that language does not have to be learned. But at its most fundamental level, Pinker does not mean that a language --- the English language, or the Chinese language, or the French language --- does not have to be learned. Humans are not born with genes for English, Chinese, or French language; specific languages are not inherited. At the biological level, we are born with a capacity for language and speech and a capacity for learning a language and speaking that language. In support of his claim that language capacity is a human adaptation, Pinker relies on several attributes, including the fact that it is universal across all cultures and that there are specific brain structures that recognize the rules of speech.

Levitin argues that our capacity for music and learning and creating and performing music is no different. The auditory system that detects, senses, and computes the attributes of music, as well as hands and feet that can be used to to create or establish rhythm, the vocal system that can create tone and pitch, and brain structures that uniquely relate to tone, rhythm, pitch, and chords are physical traits. "Music's evolutionary origin," Levitin writes, "is established because it is present across all humans (meeting the biologists' criterion of being widespread in a species); it has been around a long time (refuting the notion that it is merely auditory cheesecake); it involves specialized brain structures, including dedicated memory systems that can remain functional when other memory systems fail (when a physical brain system develops across all humans, we assume that it has an evolutionary basis); and it is analogous to music making in other (non-human) species. Rhythmic sequences optimally excite recurrent neural networks in mammalian brains, including feedback loops among the motor cortex, the cerebellum, and the frontal regions. Tonal systems, pitch transitions, and chords scaffold on certain properties of the auditory system that were themselves products of the physical world, of the inherent nature of vibrating objects. Our auditory system develops in ways that play on the relation between scales and the overtone series. Musical novelty attracts attention and overcomes boredom, increasing memorability."

Like the English, Chinese or French languages, we still need to learn classical music, folk music, jazz music, and rock and roll music and we need to learn how to perform (speak) these different types of music. And we create technologies for performing music, just like we have created technologies for communicating words.

In The Information, James Gleick (see August 15, 2011 post) cites a 19th century missionary's experience in Africa with tribesmen who communicated across great distances with drum beats, on the one hand an early form of Morse Code, and on the other hand, the drumming relied just as much on rhythm as well as the tone from the beat for conveying meaning. Although it will likely prove impossible to determine, I do not think we can rule out that music (not the same kind of music we think of today) may have been an early prototype for language. Linguistics has led to the discovery that the human brain has formal rules for language syntax. Is the brain not hardwired with formal rules for mathematics and music as well?

Pascal Boyer writes in Religion Explained, " The fact that the brain comes equipped with many specialized inferences and can run them in the decoupled mode may explain why humans the world over engage in a host of activities that carry no clear adaptive value. To illustrate this, consider the auditory cortex of humans, which must perform several complicated tasks. One of these is to sort out the sounds of language from other noises. Information about noises is sent to associative cortical areas that categorize the sounds and identify the nature of their source. Information about the source's location is handled by other specialized circuitry and sent to specific systems. The auditory system must also isolate the sounds of language. All normal humans have the ability to segment a stream of sound emerging from someone else's mouth in terms of isolated sounds, then send this purified representation to cortical areas specialized in word identification. To turn a stream into segments, the system must pay attention to the specific frequencies that define each vowel and the complex noises of consonants, as well as their duration and their effects on each other. To do this, the auditory cortex comprises different subsystems some of which specialize in pure tones and others in more complex stimuli. All this is clearly part of a complex, evolved architecture specialized in fine-grained sound analysis, a task of obvious adaptive value for a species that depends on speech for virtually all communication. But it is also has the interesting consequence that humans are predisposed to detect, produce, remember, and enjoy music. This is a human universal. There is no human society without some musical tradition. Although the traditions are very different, some principles can be found everywhere. For instance, musical sounds are always closer to pure sound than to noise. The equivalence between octaves and the privileged role of particular intervals like fifths and fourths are consequences of the organization of the cortex. To exaggerate a little, what you get from musical sounds are super-vowels (the pure frequencies as opposed to the mixed ones that define ordinary vowels) and pure consonants (produced by rhythmic instruments and the attack of most instruments). These properties make music an intensified form of sound experience from which the cortex receives purified and therefore intense doses of what usually activates it. So music is not really a direct product of our dispositions but a cultural product that is particularly successful because it activates some of our capacities in a particularly intense way." Boyer adds, "This phenomenon is not unique to music. Humans everywhere also fill their environments with artifacts that overstimulate their visual cortex, for instance by providing pure saturated color instead of dull browns and greens of their familiar environment. . . . These activities recruit our cognitive capacities in ways that make some cultural artifacts very salient and likely to be transmitted."

My own view is that language and music are means of communicating information and that language and music were preceded by proto-language and proto-music, both probably emerging in the same relative human time period. Both, in my view, were likely essential to human evolution as a social species. It also may be true, as Darwin surmised, that music was favored by sexual selection pressures. I think back to the views of V.S. Ramachandran (see October 25, 2011 post) attempting to resolve the discrepancy of views between Steven Pinker and S.J. Gould on language and evolution. For Ramanchandran, language did not evolve from some general mechanism for thinking (Gould), but neither did it evolve specifically for purposes of communication (Pinker). What is innate and what evolved, says Ramachandran, is the competence to acquire rules of language. The actual acquisition of language occurs as a result of social interaction. Ramachandran believes that language was enabled by cross linkages in the brain between different motor maps (e.g. the area responsible for manual gestures and the area responsible for orafacial movements). Can we say that what is innate about music is the competence to acquire rules of music, and that the actual acquisition of music occurs as a result of social interaction? If we think of music simply (at least initially) in terms of rhythm and vocal intonation, there is little to separate music and language including symbolic attachments. The most significant difference, however, is that music appears to reach and appeal to human emotions in a way that language perhaps does not. (See January 14, 2012 post and November 6, 2011 post).

Neuroscientist Daniel J. Levitin has made his career studying music and the human brain. In This Is Your Brain on Music, Levitin explains each of the attributes of music --- pitch, rhythm, tempo, contour, timbre, loudness, reverberation, meter, key, melody, and harmony --- and describes how the brain's architecture is essentially hardwired to deal with each element. "Different aspects of music are handled by different neural regions --- the brain uses functional segregation for music processing, and employs a system of feature detectors whose job it is to analyze specific aspects of the musical signal such as pitch, tempo, timbre, and so on. Some of the music processing has points in common with the operations required to analyze other sounds; understanding speech, for example, requires that we segregate a flurry of sounds in words, sentences, and phrases, and that we are able to understand aspects beyond the words, such as sarcasm. Several different dimensions of a musical sound need to be analyzed --- usually involving several quasi-independent neural processes --- and they need to be brought together to form a coherent representation of what we are listening to."

When we comprehend music, not as a song, but in terms of its attributes --- pitch, rhythm, tempo, contour, timbre, loudness, reverberation, meter, key, melody, and harmony --- we can recognize that these are not "technologies" as Pinker refers to music.

In the discussion of Christof Wolff's biography of J.S. Bach (see January 14, 2012 post), I mentioned the long-associated relationship of music and mathematics. Steven Pinker describes our "mathematical intuition" --- babies have the capacity to register quantities very early, which may not necessarily involve counting as we know it, but to distinguish between more or less and later to distinguish intuitively in terms of probabilities. From early mathematical intuition emerges human activity such as counting, measuring, shaping, estimating, moving, and proving. Each of these activities leads to more formal mathematical reasoning: counting (arithmetic), measuring (real numbers, calculus) shaping (geometry, topology) estimating (probability, statistics), moving (mechanics, calculus, dynamics), proving (logic). Formal mathematics emerges from our mathematical intuition, says Pinker. This same reasoning informs me that formal music emerges from our musical intuition --- our capacity for appreciating, learning, creating, and performing music.

While music exploits some of the same neural pathways that speech and language exploit, the fact that there are specially evolved components of the brain that are used in processing some of the elements of music would suggest that our capacity to appreciate, learn, and manipulate the attributes of music had some independent evolutionary value. Levitin observes that music "technology" has been around a long time --- at least 60,000 years based on musical artifacts that have been uncovered. But our capacity for music --- by which I mean our capacity for appreciating, learning, creating and performing music --- must have preceded the creation of musical artifact: there is music in song; there is music in tapping fingers and feet, which does not require a flute or drum. The origins of human language and whether it preceded music are, like the origins of music, murky. There is evidence that human language is at least 50,000 - 100,000 years old. For those who subscribe to the view that a FoxP2 gene mutation contributed to the development of human speech, that might put language in the 50,000 - 60,000 years ago range, about the same time as the oldest age of musical artifacts. It is therefore not entirely outside the realm of plausibility that our language instincts and our music instincts co-evolved or that one only slightly --- in the eons of evolutionary timescale --- preceded the other in human evolution.

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