The Pleasure Instinct: Why We Crave Adventure, Chocolate, Pheromones, and Music - Gene Wallenstein (2008)
Part III. The Pleasure Instinct and the Modern Experience
Chapter 10. Pleasure from Repetition and Rhythm
It appears probable that the progenitors of man, either males or females or both sexes, before acquiring the power of expressing their mutual love in articulate language, endeavored to charm each other with musical notes and rhythm.
—Charles Darwin, The Descent of Man
Existence equals pulsation.
—Ellen Dissanayake, Homoaestheticus
As we saw earlier, our innate preferences for proportion and symmetry have been crafted by the pleasure instinct as a means to encourage newborns, toddlers, and older children to seek out optimal forms of spatial stimulation to fine-tune the developing visual system during synaptogenesis and synaptic pruning (see chapter 8). In the previous chapter, we discussed how this preference has been co-opted during our species’ phylogenetic history through sexual selection, since such visual features can also be used as fitness indicators for mate identification and mate choice. In this chapter we will consider a temporal example and examine how our innate preference for repetition and rhythm impact many of our everyday behaviors, some of which may also be magnified through sexual selection.
The development of the primary auditory cortex and associated brain structures of all mammals depends critically on the precisely timed expression of key genes triggered when the organism experiences environmentally relevant stimuli to fine-tune the system. As was remarked earlier, the details of development are not in the genes, but rather in the patterns of gene expression. Between the twenty-fifth and thirtieth weeks of gestation, fetuses become sensitive to sounds and will move in relation to Mother’s voice especially. But beyond Mother’s voice, they also hear the steady rhythm of her heartbeat and respiration.
After birth, infants continue to seek out certain forms of auditory stimulation, particularly those that are repetitious and rhythmic. For instance, newborns and infants are extremely sensitive to the prosodic elements of speech, those that are rich in emotional meaning. Of course, prosody is the backbeat of the well-known singsong style of motherese that dominates parent-infant dialogue during the first year of life, with its emphasis on simple pitch contours, broad pitch range, and syllable repetition. Experiencing acoustic rhythm during the latter period of gestation and then as a newborn and toddler seems to be a key requirement for normal growth and maturation of the neural systems that process auditory information. Recall from chapter 7 the experiments by neurobiologists Michael Merzenich and Edward Chang of the University of California at San Francisco showing that newborn rats failed to develop a normal auditory cortex when reared in an environment that consisted of continuous white noise. After only a few months, the scientists found significant physiological and anatomical abnormalities in the auditory cortex of the noise-reared rats when compared to rats raised in a normal acoustic environment. Moreover, these abnormalities persisted long after the experiment ended. Most interesting of all, when the noise-reared rats were later exposed to repetitious and highly structured sounds, their auditory cortex rewired and they regained most of the structural and physiological markers that were observed in normal rats.
Rhythm also seems to have a calming effect on newborns and children through several sensory modes. For instance, it is commonly known that older infants, children, and even adults employ various “comfort actions” of rocking back and forth, or doing some other form of rhythmic, repetitive action to relieve tension or stress. Various religious groups practice meditation and prayer using a combination of rhythmic chanting, rocking, and repetition of key phrases. Babies as young as four months old are calmed by repetitive sounds containing consonant rather than dissonant intervals. Auditory rhythms built using intervals such as the “perfect fifth,” with a pitch difference of seven semitones, or the “perfect fourth,” with a pitch difference of five semitones, are calming to babies and adults from all cultures. Hence the experience of repetition and rhythm is critically important during brain development and can have a marked impact on the behavior of babies, children, and adults.
Indeed, most parents might observe that their babies tend to self-stimulate their brain growth by producing highly repetitious and rhythmic sounds. Ren, our latest arrival who is now seven months old, does exactly the things Kai did at this age. She seems to take great pleasure in quickly repeating the same syllable, often with slight variation in pitch toward the end of a series—her own, babbling version of motherese. She also demonstrates innovation by abruptly changing the melody slightly by alternating syllables with different pitch—beep, bop, beep, bop. She has not experienced all of these individual melodies, yet she is clearly able to take basic sounds and string them into novel series, and she does so with great joy.
An early preference for experiencing repetitious and rhythmic stimulation could have a profound effect on many forms of adult behavior. Indeed, such preferences may lead to the development of our fondness for a host of pleasurable phenomena such as music production and perception, dance, poetry, and ritualistic behaviors, to name but a few. As an example, let us consider music, since it has received the most recent attention in terms of its evolutionary origins.
The notion of the extended phenotype was made popular by the evolutionary biologist Richard Dawkins. In general, the phenotype refers to an observable quality of an organism such as its development, morphology, or behavior. This is distinguished from the term genotype, which refers to the set of hereditary instructions an organism contains. It is fairly well accepted that the phenotype can be influenced by three primary factors—the organism’s genotype, transmitted epigenetic factors, and nonhereditary environmental factors. Dawkins argued that the classic idea of the phenotype was too restrictive, since it focused primarily on the phenotypic expression of genes in the organism’s own body. In his popular book The Extended Phenotype, he wrote, “An animal’s behaviour tends to maximize the survival of the genes for that behaviour, whether or not those genes happen to be in the body of the particular animal performing it.” Genes have a long reach in that they may code preferences for a trait or behavior in one organism that, through sexual selection, promotes the emergence of the trait or behavior in others.This is a similar scenario to what we saw with a preference for symmetry and may help us understand how an innate preference for acoustic repetition and rhythm, in the service of brain development, could lead to the evolution of music production.
An appetite for music is ubiquitous among humans. It seems that evidence of music production pops up wherever there are relatively stable human social groups. And music production has been around for quite a while. Percussive and flutelike instruments have been found at Homo sapiens sites throughout Europe and Asia dating as far back as a hundred thousand years. Archaeologists have also found a bone flute at a Neanderthal site near Idrija, in northwestern Slovenia. This flute was made from the polished thighbone of a bear and consisted of four carefully aligned holes drilled into one side. Strikingly similar bone flutes have been discovered at Homo sapiens sites dated between forty thousand and eighty thousand years old.
Traditionally, evolutionary biologists have limited their forays into the study of how music may have evolved. Musicologists and theorists, similarly, have not been greatly concerned with the origins of music or its adaptive value. My sense is that this neglect from both sides is primarily because music has not been viewed as a behavior that has obvious survival value. But as we have discussed in previous chapters, evolution is driven by genes that survive long enough in one organism to be passed on to another organism ad infinitum. Mere survival in a single host is not the endgame of evolution. Darwin himself believed that the evolution of music production and enjoyment was best understood as a sexually selected adaptation.
In his recent book The Singing Neanderthals, anthropologist Steven Mithen argued that the conventional wisdom that music has no direct survival value is dead wrong. Rather, he suggests that in addition to its potential importance in sexual selection, our prelinguistic ancestors relied on music as a means to facilitate communication and cooperation.You might think that the term “cooperation” suggests a need for employing group selection as a theoretical driver of music as an adaptation.4 On the contrary, there is no need to invoke group selection, since one could argue that music production and perception have direct benefits for individuals (and the propagation of their genes) with a strong sense of alliance to the group. Such individuals are better protected from predators and enjoy the many survival advantages tied to group participation such as coordinated foraging, technology sharing, and rearing of offspring.
The evolutionary psychologist Geoffrey Miller of the University of New Mexico has taken a slightly different route. Following Darwin’s lead, he suggests that music production and perception resulted strictly from sexual selection mechanisms. In an interesting retrospective study, Miller took random samples from entries in major musical encyclopedias (more than eighteen hundred samples of jazz albums, more than fifteen hundred rock albums, and more than thirty-eight hundred classic music works). He notes that from this sample,“males produced about 10 times as much music as females, and their musical output peaked in young adulthood, around age 30, near the time of peak mating effort and peak mating activity.” This pattern of results is consistent with a large body of data showing that adaptations for courtship display (across many different species) tend to be sexually dimorphic (exaggerated in one sex) and emerge when the organism reaches sexual maturity. Of course, this study has limitations in that only those individuals with a high degree of professional success as musicians have been recorded in such encyclopedias. There may be key differences between the demographic distributions of everyday, generic musicians who just like to play and listen to music for the fun of fit and the distributions of professionals who have achieved some degree of popular success.
Music production on the African savanna during the time of our hunter-gatherer ancestors was certainly not the complicated, technological affair it is today. Most likely it was a group activity, as it is in many modern tribal societies. Moreover, if ancestral music is similar to what one sees in modern hunter-gatherer societies, it was probably typically accompanied by dance. It is difficult to imagine the hunter-gatherer equivalent to the modern-day jazz concert, with the performers up front surrounded by a much larger group of passive listeners just sitting around.The suggestion I favor is that music and dance were closely aligned in ancient times and served as proxies for fitness, just like symmetry. The primary difference is that body symmetry is a morphological phenotypic trait that can be directly correlated to a host of fitness metrics (see chapter 9), whereas music production and dance are phenotypic behaviors.Thus it might prove more difficult to show how music production is related to fitness. But as Dawkins and others have observed, examples abound in the animal signaling literature where a call, song, howl, or growl has evolved as a courtship display through sexual selection.
Might music production and perception be viewed as having evolved through sexual selection processes as a courtship display? Let us suppose that a preference for repetitious and rhythmic acoustic sounds first emerged as a survival mechanism linked to advantages in brain development. As we have seen in earlier chapters, the preference for repetitious and rhythmic sounds by newborns and babies prompts them to experience as much of these stimuli as possible, which in turn facilitates normal brain growth and maturation during synaptogenesis and synaptic pruning. Studies in rodents and primates have found that a lack of exposure to patterned acoustic stimuli immediately after birth and the months that follow has profound effects on the physiological and anatomical brain structures responsible for audition. These changes to normal brain physiology and anatomy produce marked deficits in normal hearing and functioning. Organisms with deficits in normal audition might have a greater risk of predation (since they can’t hear a predator charging from behind) and other general safety concerns that decrease their likelihood of surviving to reproductive age. A receiver bias such as a preference for repetitious and rhythmic sounds would thus have survival value and could certainly have evolved through natural selection.
But how does the pleasure we naturally find in rhythm lead to the eventual production of Schubert’s String Quintet in C Major or Rhapsody in Blue? There is evidence suggesting that the evolution of music production has been driven by both natural and sexual selection mechanisms. Clearly, music has effects on social communication and cohesiveness that may benefit the individual’s likelihood of survival. My sense, however, is that sexual selection has played as important a role in the evolution of music production as natural selection. Just as was the case for body symmetry, it is possible that an innate receiver bias in the form of a preference for repetitious and rhythmic sounds could have been co-opted as a courtship display through sexual selection.The fact that music is such an elaborate and complex adaptation makes for an even more compelling case. If a preference for rhythmic sounds becomes genetically correlated with the production of rhythmic sounds as a behavioral trait, a positive feedback loop could occur, leading to a Fisherian runaway process. Comparable to the peacock’s plume, this might lead to ever more elaborate displays to vie for the attention of the opposite sex. The trouble with this argument is that it is considerably easier to suggest that music evolved as a sexually selected courtship display than it is to find actual data supporting the claim.
Ironically, going back all the way to Darwin, there are far better examples of how animal signaling—such as calls and songs—serve as courtship displays in species of frogs and birds than how making music may serve a similar purpose in humans. Many species of birds, whales, and primates (for example, gibbons) use song as a sexual display during breeding season. Some songbirds such as the winter wren use bits and pieces from songs they have heard, and reassemble them to form new phrases. That is, they exhibit learning similar to that seen in human music making. Hence, winter wrens can often sing hundreds of different songs. There is now evidence that females from several bird species such as blackbirds, mockingbirds, and warblers prefer males that generate larger song repertoires. Many species of birds also sing songs that have key components such as refrains, symmetry, and reprises similar to what is seen in human music.
So there is a precedent for using signals that have some components in common with human music as a form of courtship display during mating. To demonstrate that human musicality evolved through sexual selection as a result of an initial receiver bias for repetition and rhythmicity, however, we need strong evidence to support a number of basic necessary conditions (similar to the conditions we generated when discussing symmetry and proportion).
Condition 1 The preference for repetition and rhythmicity is expressed at or very near birth. We have provided key evidence for this condition existing in audition in chapter 7 and for other sensory modalities in earlier chapters.
Condition 2 The preference for repetition and rhythmicity generalizes across many object forms. As we saw in earlier chapters, infants take pleasure in both perceiving and producing repetition and rhythm in a number of different domains, including vision, somatic, vestibular (for example, rocking back and forth), and audition. Hence this condition is likely met given the accumulated evidence.
Condition 3 Music has signal properties (qualitative and quantitative) that are similar to the repetitious and rhythmic stimuli that infants enjoy and produce. One way of providing evidence for this condition is to examine the statistical properties of the rhythmic auditory signals most enjoyed by infants and demonstrate a correspondence in music.There is some evidence for this already. As we have seen, infants and adults alike prefer rhythms built from consonant intervals such as the perfect fifth and perfect fourth, with small pitch differences in neighboring tones over dissonant intervals with high pitch differences. It has also been shown that infants prefer rhythms with sharply rising or falling pitch contours.This signal quality is common to both language (that is, prosodic cues) and music. Other evidence might come from showing that the repetitious and rhythmic auditory signals that infants generate as a form of self-stimulation have similar properties to those seen in music.To date this type of study has been limited to demonstrating that some of the key components of musical expression also occur in infant babbling—for instance, repetition, abrupt changes in pitch contour, reprises, and refrains.
Condition 4 Music production is a reliable marker of phenotypic quality. Since music and dance have costs associated with their production, this behavior might serve as a potential fitness indicator. Fitness itself is a vague term. Most often when we hear the word “fitness,” we think of proxies such as general health, avoiding certain illnesses, heterozygosity in select genes, or any number of other traits. But for Homo sapiens with sophisticated cognitive functioning, fitness of the mind may also have been an important indicator. As we have seen, handicaps are often reliable fitness indicators because they are generated at the expense of diverting precious energy from basic system functioning (for example, from growth and immunocompetence) and are often very conspicuous signals that could attract the attention of predators (they are called ornaments for good reason). Music production and dance require large reserves of metabolic energy even for short periods, but we know that modern tribal societies often have ritualistic music and dance that can last many hours and even days. The closest Western equivalent is probably the all-night rave, where young adults typically in their twenties dance nearly continuously from dusk to dawn.
Music and dance production also consume vast amounts of metabolic energy used by the brain to derive creative expressions that will attract the attention of potential mates. The overwhelming majority of energetic costs associated with being a big-brained hominid are linked to that big brain. No body part or system even comes close in its energy requirements to the ongoing metabolic demands of our brain. Hence traits that are reliably linked to increasing the already high energy demands of the brain would be honest indicators of fitness in this broader sense.
Miller has made some suggestions in this regard.“Dancing reveals aerobic fitness, coordination, strength, and health. Because nervousness interferes with fine motor control, including voice control, singing in key may reveal self-confidence, status, and extroversion. Rhythm may reveal the brain’s capacity for sequencing complex movements reliably, and the efficiency and flexibility of the brain’s ‘central pattern generators.’ Likewise, virtuosic performance of instrumental music may reveal motor coordination, capacity for automating complex learned behaviors, and having the time to practice.” If some of these putative associations or others could be demonstrated through empirical studies, this would represent a major step forward in showing that the evolution of music was indeed driven, at least in part, through sexual selection.
Condition 5 Adults who can produce music enjoy greater mating success (when all other potential confounding variables are controlled) than their unmusical counterparts. As with condition 4, this condition might also be extended to include dance. There is, of course, the anecdotal evidence about rock stars having magnetic-like attraction for members of the opposite sex, but I suspect that there are so many confounding variables (for example, confidence, extroversion, wealth, exposure, fame) that it is practically impossible to draw any meaningful conclusions from such stories. To demonstrate that this condition is true, we need evidence from prospective, well-controlled experimental studies. One line of experimentation should be designed to determine if individuals who exhibit the best dance or music production ability are viewed as more attractive than their counterparts after being matched for certain covariables such as age, gender, and key personality traits. The second line of experimentation would support condition 4 as well as condition 5 by testing whether the individuals who are seen as being the most attractive are also seen as being the fittest. Such experiments should also attempt to answer the specific dimensions of fitness that are particularly relevant to music production and dance.To my knowledge, such studies have not been conducted to date and await a motivated researcher.
Condition 6 Adults prefer repetition and rhythmic stimulation in many forms, even those unrelated to music production and perception. A growing body of data indicates that adults are attracted to repetition and rhythm in many contexts across many sensory domains. Children and adults take pleasure from certain comfort actions such as rocking back and forth or producing repetitive movements of one body part or another. Such movements are pleasing in their own right but also reduce tension and stress. Dancing, running, walking, swimming, sex, and a host of related activities are other forms of repetitive motor behavior that clearly please adults.
Language production and associated social dynamics have a very specific rhythm that can be pleasurable. Indeed, experiments have demonstrated that when speaking, people tend to choose words that fit rhythmically into their statement—a type of melodic intonation of spoken language. The pleasure some individuals find in poetry, which depends strongly on rhythm and meter, is another example of our attraction to repetition and rhythmicity.
Many nonmusical sounds of nature that are rhythmical are pleasurable to adults and children. Judging by their impressive sales, quite a few people fall asleep each night to the soothing beat of the ocean produced by a sound generator. Other options include the sound of crickets, rhythmic winds, flowing brooks, and birds. As long as there is sufficient variation in the sequence and the sounds are rich enough to reflect the natural world, the rhythm is very pleasing.
Although many studies have examined our proclivity to prefer temporal order to chaos, clearly there is a need for more systematic research to map out the full extent of the sensory domains involved. I suspect that we have just touched the surface in really understanding how this preference presents itself in everyday behaviors.
Hence we have fairly good evidence supporting conditions 1, 2, 3, and 6, and we need quite a bit of additional data to convincingly support conditions 4 and 5. But I am convinced that evidence will emerge if we make the effort to conduct carefully controlled studies.
To this point, we have discussed two very different examples—one spatial and one temporal—that illustrate the way the pleasure instinct can impact our everyday lives and behaviors. In the next chapter we will consider the manner in which the pleasure instinct places high costs on those individuals who abuse it. We are all equipped with brains that have evolved to face specific challenges and circumstances from our ancestral past. Many of these challenges and the conditions in which they originated are quite different from, and in some cases in direct opposition to, those that exist in the modern world. In a real sense, we are all of another time.The innate preferences that have been forged by the pleasure instinct to help facilitate brain growth and maturation have consequences far beyond our love of symmetry, proportion, rhythm, and repetition (to name just a few). Let us now turn toward the darker side of the pleasure instinct—addiction.