Our Senses: An Immersive Experience - Rob DeSalle 2018

Facing the Music: The Neurobiology of Music and Art

“Music is the movement of sound to reach the soul for the education of its virtue.” —Plato

At the risk of violating the famous comedian, actor, and musician Steve Martin’s edict about music that “talking about music is like dancing about architecture,” I will examine the sensory context of music from several perspectives. What really is music, and does it deviate from language? How did it arise in our species? After all, processes akin to music exist in other species, such as in birdsong or cetacean vocalization. Addressing this question includes looking at the neural and genetic basis of music in our species to understand its origin and possible impact on the nervous system. Also, what are neurophysiological bases of the effects of music and the sensory components involved in our perception of it?

Part of the draw to music as a sensory phenomenon is its general appeal to the brain. Music has been called everything from the thing that soothes a savage breast (Shakespeare) to cheesecake for the mind (Steven Pinker) to anything that is too stupid to be spoken (Voltaire). So, the complex relation of music with our brain and the nervous system is a critical story to understanding how our senses are involved in the creation of perception and how the unique perceptions generated by music affect our inner world of emotion and memory. The major sensory input system that receives music is the auditory system. But some humans can read music and have the capacity to “hear” it simply from reading it. Sadly, my predilection for music is as a casual listener, although I did learn to read music when I was young. Unfortunately, my capacity to read music only goes as far as knowing what the notes are supposed to mean. I can hear music in my mind when it is played in front of me, but reading musical notes now has no impact on what I can “hear.” I often have earworms, those annoying tunes that play over and over in the brain. My earworm while writing this chapter was Randy Newman’s “You’ve Got a Friend in Me” from the Toy Story movies that my three-year-old son and I love to watch together. The funny thing is that it is just the line from the title that plays over and over in my earworm. Six simple notes, associated with six syllables, have dominated the downtime of my brain for the past week. Eventually, I know I will lose this earworm, but in some ways I hope it doesn’t go away. Most earworms are irritating at the least, and distracting and distressing at worst. They are difficult to extract from the brain, and this is why Oliver Sacks calls them “brainworms” instead. My attraction to this one earworm is emotional because it is a bond to all three of my children who have watched the Toy Story movies with me, and it has become a part of my memory because even though watching any movie ninety times can be a wearisome task, these particular movies and the earworm itself have become like auditory madeleines to me.

The difficulties that geneticists have encountered in defining music associated with their attempts to unravel the genetic basis of music should be a good example of how hard it is to define music and musical ability. When using genetics to unravel a complex trait, a strong definition of the trait is needed to make any progress. So, what geneticists have done is attempt to dissect the components of music in order to uncover the genetics of this complex trait. To understand the components of music, recall that the music we hear is sound (Chapters 5 and 7), and sounds are essentially waves that cause vibrations. Our ears are inundated with sound, so what is it about music that makes us capable of hearing it and realizing it is music? There is no single characteristic that makes music music. Rather, it is a combination of characteristics about the vibrations being made that our ears detect. It turns out, depending on who you are talking to, that there are anywhere from five to eight major elements of music, and some of them are essential for an understanding of the genetic basis of musical traits. One element, pitch, is usually on everyone’s list. We have already discussed pitch as a major element of sound that is based on the frequency with which the sounds are vibrating and the size of the object that is vibrating. So, for instance, the faster the sound is vibrating and the smaller the item that is vibrating, the higher the pitch will be. Pitches exist on a spectrum from low pitch to high and are measured in hertz. Pitch and vibration frequency should not be confused, which means that pitch is sort of subjective. The range of hearing for a healthy young person is 20 to 20,000 hertz, but not all sounds in this range are considered musical. For instance, the range of pitch on a musical instrument like a piano is from 4.37 hertz (B₈ note) to 2,109.89 hertz (C₀ note). People with absolute, or perfect, pitch are able to hear a sound and to identify it as having a specific pitch without a frame of reference. Such people are easy to identify, and the majority of people with absolute pitch who have been studied are musicians.

The brains of people with perfect pitch have also been examined using brain imaging approaches, and comparisons of musicians with and without absolute pitch have been made. It turns out that a specific part of the brain, called the planum temporale, is consistently associated with perfect pitch. Because we have this brain region on both sides of our brain, the first relevant question is do the two sides of the brain differ? Imaging studies clearly show an asymmetry of the left planum temporale and the right planum temporale in people with perfect pitch. The next question then becomes how does the asymmetry arise? The fMRI studies suggest that in people with perfect pitch, there is a pruning of neural connections in the right planum temporale in childhood that renders it smaller than the left. Because the pruning occurs in early years of childhood, and hence before most musical training, it cannot be attributed to exposure to music. Rather, it is more than likely a developmental phenomenon under genetic control. Let’s take a look at how imaging the brain on music works and what the imaging tells us.

Cortical thickness is used as a metric in how brain morphology changes. The cortical thickness is used because it is correlated with more white matter and hence more neural connectivity. Greater cortical thickness of the brains of people with perfect pitch is evident in these studies, but the exact nature of the differences has only recently been made clear. The bottom line with respect to neural structure and perfect pitch is that there is an increased neural connectivity in parts of the brain in people with absolute pitch. Specifically, the leftward planum temporale region of the brain appears to be asymmetrically larger in people with absolute pitch. The experiments pinning down this neuroanatomical correlate are done very carefully using only right-handed musicians (remember that handedness sometimes influences the side of the brain where certain neural functions reside). But does this asymmetry exist because the left planum temporale has grown larger or because the right planum temporale is smaller in people with absolute pitch?

The genetic basis of absolute pitch (box 19.1) has been examined using several approaches. The tried-and-true twin study approach showed that there is a heritability of about 0.81 for perfect pitch, which means that there is a strong genetic component to the trait (remember that heritabilities range from 0.0 to 1.0, with values closer to 1.0 indicating full genetic control over the trait). Genomic techniques have attempted to localize the genetic elements involved in absolute pitch. These studies have found several regions in the genome that are linked to absolute pitch, of which one, located on chromosome 8, appears to crop up in most studies that attempt to link absolute pitch to genes. The gene focused on is important in memory and cognition. Other loci have also been forwarded as candidates, and these usually are involved in development of the inner ear.

While not exactly the genetic opposite of perfect pitch, congenital amusia involves the lack of capacity to detect pitch and a lack of ability to remember tunes. As its name implies, it runs in families, and its neuroanatomy has been worked on. Specifically, amusia has a major impact on the auditory cortex and in this context has a very different neurobiological etiology and indeed does not involve the same genes that allow absolute pitch. To date, a genetic basis for amusia has been implied, but the genetic locus affected is not known.

Another method that can be used to discover genes that might be involved in musical aptitude or preference is to ask where in the genome natural selection may have had an impact in musicians. This approach looks for genes in the genome where DNA sequences have changed in a specific extraordinary way that implies natural selection. In some tests for selection, the genome is scanned region by region to see if DNA sequences occur in nonrandom distributions. If a gene does have a profile of change where it statistically appears to be unusual, it is tagged as a potential gene involved in a specific trait. One such study looked at about 150 Finnish individuals, using musical aptitude as a means to sort through unusual signals. Their results suggest that several genes show signatures of natural selection, and some of these are involved both in the development of the inner ear and in aspects of cognition. Interestingly several of the genes that were discovered have unknown functions in humans, but the same genes are responsible for perception of songs and song production in songbirds. As I have pointed out before, these genetic studies are only as good as the characterization of the phenotype is. If one has hard time determining the phenotype, then finding the genetic correlate is going to be either difficult or misleading. Absolute pitch and amusia can be detected with simple tests, so the reliability of the genetic bases of these traits is pretty strong. Other traits that researchers have explored with regard to music are harder to pin down as phenotypes. Traits like musical aptitude, ability, and preference are a bit harder to examine, but looking at these blurrier traits gets us closer to why and how music soothes a savage breast.

BOX 19.1 | WHERE ARE THE GENES FOR PERFECT PITCH?

The specific location of the linked gene is 8q24.21. Genomic locations start with the number of the chromosome, and they next list whether the locus is on one end of the chromosome (p) or the other (q). Human chromosomes in general have a centromere in them that separates the short end (p) from the long end (q). Finally, the location of the locus is given by coordinates much like a ruler. This gene at 8q24.21 is thought to be ADCY8, or adenylase cyclase 8, which has a very specific cellular function in the cell membrane. It is also a gene that is thought to be involved in memory and cognition. Loci involved in absolute pitch might also be involved in the development of the inner ear, neural connectivity, and development. If loci involved in neural connectivity are involved, this might support the contention that absolute pitch is all about the pruning of connections in the brain.

To quantify these fuzzier musical abilities, researchers have turned to standardized tests that allow them to place people on a spectrum of values, such as the Karma Music Test. In this test, people are exposed to short, abstract sound patterns that form hierarchical musical structures because they are repeated. The person will hear several different hierarchical patterns and is then asked to discriminate among them. How accurately someone can describe the differences in the hierarchical patterns can be placed on a scale. The test is interesting because it was devised to weed out musical training as a factor in the scores. Other tests that are applied are called Seashore tests and the pitch production accuracy test. The Seashore tests consist of the subject hearing pairs of sounds with slight differences in pitch and timing. The person is then asked to discriminate between the pairs of sounds. The tests detect simpler aspects of the sensory capacity for musical aptitude such as pitch and timing. The pitch production accuracy test starts with the person hearing a sound with a specific pitch through headphones. The subject is then asked to sing the note replicating the pitch from the headphone. The performance of the person is then easily graded to give a quantitative measure of musical ability.

Musical preference is a different story when it comes to the tests for quantifying it, because the subject’s opinion of a particular kind (a genre) of music is quantified. If the participant is an infant, the attention trick described in Chapter 7 for synesthesia in infants is used. The Short Test of Music Preferences is the most widely used approach. This test presents fourteen to twenty-three music genres to the listener, who is asked to rank the genres on a scale of 1 to 7 (1 = strongly dislike and 7 = strongly like). Some researchers have gone as far as asking subjects to write essays describing musical genres or even songs. In one study, researchers pored over more than 2,500 essays written about music genres to assess the musical preferences of the study participants.

With the usual caveats about how this kind of work is done, some interesting ideas about musical aptitude and preference have been made. For instance, using the quantification of musical ability, several potential traits associated with musical aptitude have been looked at genetically. These subtraits include recognition of pitch and rhythm, music memory, music listening, singing, and musical creativity. For recognition of pitch, several loci have been pinpointed by genomic studies. Many of the genes discovered in this way are involved in the development of the nervous system or maintenance of neural tissues. A couple of the genes are specifically important in the development of the inner ear for structures like the cochlea and for the proper development of the tiny hairs in the inner ear that detect the external vibrations of sound. One gene in particular codes for a protein that appears to be important in pitch and rhythm, musical memory, and music listening. The gene’s name is AVPR1A, and it is technically known as a vasopressor, a protein that acts in regulating the amount of water the body holds and with blood pressure. Vasopressin is another name for AVP, a hormone that has been suggested to be associated with autism and is also thought to affect interpersonal behavior. Another gene thought to be involved in musical aptitude is called protocadherin, which is a membrane protein that regulates cell-to-cell adhesion. It is important in the structure of the cochlea.

Musical preference has also been studied in the context of how music affects our emotional makeup. For instance, there is a lot of work on how musical preference intersects with personality and, by extension, whether musical preference can be a predictor of personality. Some studies show a clear correlation of personality with musical preference. A large study used the five-factor model of personality that attempts to place personalities on a scale with the following descriptors: extraversion, agreeableness, conscientiousness, neuroticism, and openness to experience. These personality descriptors were examined in the context of music preference for several genres of music. The result of the survey is that lyrics and genre are correlated to personality, with personalities like openness correlated to the wilder music like punk and death metal and extraversion correlated with pop music. Indeed, researchers suggest that the one (personality) can be used to predict the other (genre) and vice versa.

Other studies reveal similar patterns indicating that individuals who are open-minded to experiences in their lives are more prone to have preferences for complex music like classical music and music considered on the cutting edge like punk rock. On the other hand, extraverts will go for pop music like the boy band music and rhythmic music like hip hop. Delinquency has also been studied as a part of the story. Using the reporting systems described above and a database of the delinquency of participants, Tom ter Bogt, Loes Keijsers, and Wim Meeus have shown that “loud, rebellious and deviant music,” such as heavy metal, goth, and punk, as well as rap and techno house music, are correlated with minor delinquency in older adolescents. Classical music and pop show no link to delinquency. These data together indicate that early musical preference might point to the direction of minor delinquency later in life. I hate to admit it, but perhaps my parents were right when they banned my playing of “The Pusher” by Steppenwolf in our house. The rock and protopunk music I listened to as a kid never landed me in jail, but I am sure that it did lead to some delinquent behavior on my part. But is delinquent behavior all bad? If you have ever been the parent of a rambunctious sixteen-year-old, then the answer might seem obvious. But some researchers suggest that the real link of music like punk and heavy metal is to openness and propensity to explore.

The kinds of genes that have been pinpointed so far that are involved in musical aptitude show us a lot about how music works in the brain. The psychological testing done to understand music preference also tells us something deeper about music. Music, in general, enters the brain through the ears, so genes that are important in the development and structure of the inner ear are involved in the primary processing of sounds like music. Once in the brain, music is processed into its component parts, and from these the brain then dictates how specific kinds of music will affect us, by inducing emotions and memories.

Thomas Schäfer and colleagues conducted a survey on more than eight hundred subjects and were able to suggest that people listen to music to “regulate arousal and mood,” to “achieve self awareness,” and as an “expression of social relatedness” (box 19.2). The first two functions were more influential than the third. It should be noted that the study focused on German-speaking people over a large range of ages (eight to eighty). Although the results of this study are very interesting with respect to defining how music is used by people, music preference itself might be highly cultural, and so it would be interesting to see how other cultures view music in this functional context.

To address the issue of cultural input into musical preference and music creation, Patrick Savage and his colleagues examined music in nine geographic regions of the world. Thirty-two musical features were examined in 304 music recordings from across the globe. Taking the cultural context out of music results in the discovery of no clear diagnosable universals across the different areas of the globe, and this suggests that music may not be the universal language of humankind that many think it is. However, eighteen of the thirty-two features of music do show a statistical global correlation, with ten of these being found in a network of relatedness, which simply means that they are connected to each other more than they are to other features. The statistical features are based on attributes of music that have been suspected to be universal, such as pitch and rhythm. Other features discovered using this approach are not commonly thought to be universals of musical preference, such as performance style and social context. Cross-cultural contexts become very important when attempting to define music and when correlating music to function, however.

BOX 19.2 | WHY WE LISTEN TO MUSIC

Thomas Schäfer suggests that music listening and preference have more than a hundred functions. By asking study participants a series of 129 questions such as the following, Schäfer and his colleagues were able to dissect preference for music into an equal number of functions.

I like music (please score on a scale of 1 = I do not at all agree to 6 = I agree completely)

____ Because it gives me intellectual stimulation.

____ Because it gives me something that is mine alone.

____ Because it gives me goose bumps.

____ Because it addresses my sense of aesthetics.

____ Because it reminds me of a particular person.

____ Because it makes me feel my body.

____ Because I can enjoy it as art.

. . . and so on, for a total of 129 questions relevant to 129 possible functions of music.

The physiological response of the body to music through its action on the brain has also been studied. The experiments to examine this aspect of music involve contrasting the physiological response of people to stress after listening to three background sounds—Gregorio Allegri’s “Miserere” (a choral piece written in the seventeenth century for the Sistine Chapel), the sound of rippling water, and silence. These sounds are followed by experimenter-induced stress to the subject. Each participant is then measured for physiological markers of stress, such as cortisol levels, heart rate, and sinus arrhythmia, as well as self-reported stress and anxiety levels. The first part of the survey sounds okay and perhaps even fun, especially if you get to listen to the “Miserere,” which is a beautifully soothing piece of music. But the stress part sounds a little like torture. The researchers doing this survey thought of two of the most stress-inducing situations an adult could go through without causing psychological havoc—a job interview and the task of solving a difficult arithmetic problem in front of an audience. I can attest to the stress induced by the second task of doing math in front of people. When I started my academic career, I took a position as an assistant professor at Yale University. I had never taught before but felt some confidence in my ability to explain population genetics, which can be very mathematical at times. During my first lecture at Yale, I decided to derive a mathematical equation without notes for an undergraduate genetics class. I started okay with the basic parts of the equation but quickly got lost, and this in front of a hundred Yale undergrads. My stress level rose massively as I tried to recover the missing parts of the equation, and then it happened. I was booed by the students, and my stress level shot through the roof. So, while it might be slightly tortuous to induce stress in this way, I can attest to it working quite well at inducing stress. Of course, the idea of the study is to see if the soothing “Miserere” music and the potentially soothing sound of water could alleviate some of the stress applied after listening to the two sounds. The results indicate that listening to “Miserere” (relaxing music) before the application of stress does not make one immune to stress. However, the musical treatment before stress induction means that an individual will recover faster from the induced stress.

Stress is only one emotional and physiological response that can be modulated by music. Using a clever animation to reflect emotions, Thalia Wheatley and her colleagues examined the emotional context of music in Dartmouth College students and members of the Kreung tribe in Cambodia. They used a clever device called Mr. Ball to gauge emotional level and musical preference.

A red bouncing ball, Mr. Ball can be animated and his physical appearance manipulated. His physical appearance is controlled by five sliding bars, which a person can move to represent an emotion. In one animation, a group of subjects was asked to manipulate Mr. Ball using one of the five sliders to show happiness, sadness, peacefulness, anger, or fear. In a different animation, the sliders represented aspects of music matched with aspects of motion. So, for instance, slider number 1 controlled the rate of bouncing and the speed of the music. Slider 2 controlled jittery movements and the jitteriness of the music. Smooth movement and consonant musical sounds were controlled by the third slider. The fourth slider controlled size of move of steps and move of notes, and the fifth slider controlled the direction of the steps, or whether the music moved to higher notes or lower notes. The key to the experiment is that one group of subjects would use Mr. Ball’s movement (and not hear music) as a way to express the emotion, and the other would use music (and not see movement) to express the requested emotion.

Interestingly, when a person was asked to make say, an angry Mr. Ball, the sliding bars were placed in nearly identical positions for music and for the movement of Mr. Ball (fig. 19.1). This result was also obtained when Cambodian people from the Kreung tribe were asked to do the same experiment, indicating a cross-cultural context for the task. This experiment actually addresses questions about the cross-modality of sight and sound, but in an emotional context. The result suggests that both motion and music activate brain regions connected to emotions that are deep in the brain in the limbic system, where emotions are processed. This undeniable link of emotions to music is also demonstrable with literature and art. The differences are in how the sensory information gets into the brain and where it travels from this entrance.

In 2005, two years before Jonah Lehrer suggested that Proust was a neuroscientist, Patrick Cavanagh, a neurobiologist, pointed out in the journal Nature that artists have had a centuries-long and wonderful hold on neurobiology and on the visual process. He presented several intriguing examples from Renaissance art where artists tricked the senses with shading or lighting. The examples involve improbable lighting or shading techniques that the observer rarely if ever notices. These tricks include using shadows and shading of buildings to create perspective, at the cost of impossible physical attributes of the shadows and shading. He made the very interesting point that certain attributes of art have not changed for thousands of years. For instance, line drawing was established early on in the history of known art. The amazing renderings of animals in cave drawings like those from Lascaux, France, from fifteen thousand years ago are similar to drawings of animals from the fifth century and also to modern line drawings. Cavanagh points out that early artists experimented with drawing lines that their viewers would be able to perceive and identify as the objects they were drawing, and they did this in the earliest known portraits of animals. This technique is also evident in sculptures and goes back just as far as the Lascaux drawings, as evidenced by the superb carving of a horse from the rock shelter known as the Abri de Cap Blanc in France (also fifteen thousand years old).

Figure 19.1. Mr. Ball in different guises (happy on the left, angry on the right), as imposed by subjects of Wheatley and colleagues’ surveys.

Once this technique was learned, the rest becomes what art is all about—creating interesting and intriguing and baffling ways of playing with it. As V. S. Ramachandran, the well-known neuroscientist (see Chapter 12) and contributor to ideas about art and neuroscience, says, “The purpose of art is to enhance, transcend, or indeed even to distort reality.” This basic knowledge is an artistic technique that cannot be “unlearned” and is emblazoned in the brains of artists and their patrons. Ramachandran has been criticized for the reductionism in his explanation of art as a neurobiological process because he minimizes emotion, memory, and intellectual intention. But what Ramachandran suggests is a good start, because after all, art begins with our senses. If there are complicated feedback loops with emotions and memory and intention, then this is all secondary to the initial impression art makes on us. Cavanagh puts it into perspective with the following statement: “Discrepancies between the real world and the world depicted by artists reveal as much about the brain within us as the artist reveals about the world around us.” And so, studying artists and their patrons while viewing art has become an interesting and productive way to discover not only what art is made of from a neurobiological perspective but also how our brains work in general.

Other artistic techniques, such as transparency in paintings, the use of two dimensions to convey three-dimensional scenes, incompletely drawn out art that begs the viewer to fill things in, and reflections, also have a neurobiological tinge to them. Here again Cavanagh gives some beautiful examples of art with neurobiological explanations for the visual effects they produce. (Readers should consult the original article in Nature to get a sense for the neurobiologist-artist connection.)

One of my favorite art movements is cubism. In many cases, cubist art shows just enough of the subject to get the brain to identify what might be the information the eyes have collected. I enjoy cubist works because they induce a basic biological response in me when I view them and then let my imagination go wild. This capacity to take cubist artwork and identify the objects in it is a neurological function that our species more than likely evolved in common ancestors far in the past. Evolutionarily it is important for any visual information the retina collects to be identified rapidly so that we can decide whether to run away from the object, eat it, or try to mate with it. Sometimes in nature retinas only collect information for fragments of the object: think of the proverbial snake in the grass or a hyena snout sticking out from behind a rock. But organisms still need to make quick decisions about the object that might be essential for survival. Cubism has exploited this basic visual neural function of “filling in” and has manipulated this function to produce some of the most intriguing and inspiring artwork around. Finally, cubism doesn’t appeal only to our so-called lizard or reptilian brain. It has a broader and more widespread effect because waves of signals are sent throughout the brain after the object is recognized in the inner part of the brain. More than likely this information travels to the same places in the brain that information on an abstract piece of art, such as an action painting by Jackson Pollock, or a Renaissance oil painting, such as Leonardo da Vinci’s Mona Lisa, does for postprocessing.

One way to dissect what is involved in art perception is to simulate art by using obvious aspects of art that are well-defined to produce art and then dissect the response that people have to the simulated art. Using computer-simulated art generated by what is called the Painting Fool, researchers have made some inroads into dissecting how art is made at the neurological level.

This computer program is the brainchild of Simon Colton and has its own website for producing simulated art. After using it for a while, I got the sense that the Painting Fool has a personality and certain degree of pride in its work, and it makes some very interesting visual products. And indeed, the Painting Fool has been programmed to simulate the rational moves and techniques of an artist as a piece of art is generated. Researchers can tip this approach on its head and program the Painting Fool to be irrational and ask the question, What happens? Oddly enough, the Painting Fool produces very trippy, hallucinogenic art when the rational rules of art that it usually works by are tweaked. This result suggests that creativity and hallucinations are connected in an interesting and compelling way in art. One need only look to the trippy art of the surrealists to see the logic behind this approach.

Artistic capacity has been observed to run in families, suggesting a genetic component. Any genetic study focused on art almost obligatorily concerns visual input and the assessment of aesthetic preference. The retina usually is the portal through which information about art travels into the nervous system. Hence, any trait tightly linked to enhanced functioning of the retina might be similar to perfect pitch with music and hence perhaps a direct connection to art. Because we know a lot about the structure of the retina, looking at the component parts of this structure in our eyes could be a good inroad to linking genes with art perception and preference. The first and foremost requirement for the structure of the retina in viewing art is the proper development of rods and cones. Without these cells that collect light waves, blindness results. This doesn’t mean that blind people cannot enjoy art, because they still have the sense of touch. A visit to see Leonardo da Vinci’s Last Supper fresco at the convent of Santa Maria delle Grazie in Milan is a stunning visual experience. But off to the side in the grand room where the Last Supper is painted lies a three-dimensional relief sculpture of the famous scene. It is placed there specifically for the blind, and even for someone with sight, if one closes the eyes and feels the relief with the hands the experience is also very moving.

The next structural aspect of the retina would be what kinds of rods and cones exist in the retina, and this aspect of the retina concerns the opsins embedded in the rod and cone membranes. As we saw in Chapter 9, some people, known as tetrachromats, have extra opsin genes that make proteins that are sensitive to colors that normal people, or trichromats, cannot see. In addition to perceiving color, the opsins in rod and cone cells collect information on shading and depth perception. Some researchers have examined people who are both tetrachromats and artists to see if there is a correlation of this trait with art production and perception. These studies suggest that tetrachromats experience and produce art in different ways than normal trichromats. This doesn’t mean that tetrachromats make better art or are better at perception than us normal trichromats; rather, the paintings they produce are done in unique sensory manners. Other aspects of vision also enhance how we collect and interpret light waves. The visual pathway in the human brain is very well known, and perhaps some of the neural connections in these areas of the brain will eventually be shown to have an impact on how we make and perceive art.

Our senses take information from the outside world and transform it to perception and then to meaning. It should be clear from the examples in this chapter that the initial processes used to get the information into the brain are very similar in most higher organisms, especially vertebrates. However, what should be equally clear is that our species turns the initial information from the outer world into something unique in comparison to other organisms on this planet. It is stunning, though, to realize that our species is continually attempting to improve our senses and therefore to improve our perception of the outer world. We basically have no limits to how we can and will perceive the outer world. The lack of limits means that we have the power to help correct deficiencies in some of our fellow humans with respect to the senses. But it also means that various parts of the universe that we have not so far been able to see, feel, taste, smell, and hear will eventually be made perceivable to us by development of new technologies that enhance those senses.