The Pleasure Instinct: Why We Crave Adventure, Chocolate, Pheromones, and Music (2 page)

Until recently, scientists have concentrated almost exclusively on studying how social and cultural factors shape emotions. Academics have typically shied away from using evolutionary principles to study slippery subjects such as pleasure because they often fear that such an approach leaves little or no room for the role of experience. We’ve heard it so many times:“People like things because they learn to like them, not because their genes tell them to.” We’re not programmed with innate preferences, the argument goes; we learn what is pleasurable through trial and error.And this is often the case. Yet studies have shown that rather general biases are present immediately after birth. For example, newborns prefer the taste of sweets to sours; a smile to an expressionless face; symmetrical to asymmetrical objects and scenes; and rhythmic to random sounds. These preferences emerge long before the infant ever encounters a cookie or hears its first joke. This book explores the many innate proclivities that have evolved in humans as a result of our pleasure instinct, and examines how they dramatically shape our brains, behaviors, thoughts, and feelings.

In the last twenty years a scientific revolution has been under way that marks a significant departure from how human behavior has been studied in the past. The new thinking rests on the firm belief that to make sense of human nature, one must consider how the human mind was molded by both natural and sexual selection. Instead of simply asking, How does the mind solve problem X? a better question is,Why was that particular mind/brain mechanism selected for during our earlier history as hunter-gatherers?

Some claim this revolution began with the 1975 publication of E. O. Wilson’s now classic book
Sociobiology
, which examined the way selection factors influence reproduction strategies. Rarely has a scientific text produced such a strong sense of political outrage, particularly among social critics who saw it as a scientific justification for patriarchal societies. Posters were placed all over Harvard University inviting students to attend and disrupt Wilson’s classes with noise-makers, and he was attacked in the press by many of his colleagues.

Yet the revolution has continued to gather steam, finding support and a more solid foundation from such diverse fields as molecular biology, behavioral genetics, cognitive psychology, cultural anthropology, and neuroscience. Sociobiology and its heir apparent, evolutionary psychology, have now grown at an exponential rate, with thousands of researchers using them as the main paradigms through which they investigate human behavior and indeed culture.

For our purposes, we will use both evolutionary and developmental principles to help us navigate the rambling terrain of pleasure—from its ancient landmasses that gave rise to modern landscapes, to its largely unexplored hinterlands. Pleasure, as we shall see, is the “common currency” that regulates the way humans self-stimulate their own brain growth and maturation. Human babies, for instance, are exceedingly discriminating in what they prefer to look at, listen to, feel, taste, and smell. These innate biases—from a love of primary colors, to a fondness for prosody—ensure that infants seek out the best kinds of sensory experiences for promoting normal brain development in their early years of life. Such biases persist well beyond the critical periods that every parent is familiar with, and form a system of positive reinforcers that profoundly impact adult cognition and behavior. In the chapters that follow we will address long-standing questions and learn why pleasure is ultimately a regulator of development. The issues that arise are at the very core of what it means to be human, and give us a glimpse of what we can reasonably expect of human nature. Why did pleasure evolve? What are the evolutionary advantages, biological realities, and consequences of pleasure?

 

This is but a small sampling of the questions that arise naturally when we ask: Why does pleasure exist? Fundamental answers to these questions will not be found by generating a hodgepodge of disjointed theories, each tied to a particular issue. Instead, when asked against the backdrop of evolution, they reveal the framework of a new worldview that is beginning to change the way we think about human nature.The story of how the pleasure instinct evolved and continues to function today begins with our first steps into the cognitive niche.

The next two chapters of this book are dedicated to exploring these initial steps into the cognitive niche and provide a conceptual foundation for understanding the role of pleasure in the evolution of our species. Chapters 4 through 8 detail how the pleasure instinct facilitates normal brain growth and development in each of the five primary senses—touch, taste, smell, audition, and vision. Chapters 9 through 11 provide three examples of how the pleasure instinct impacts our everyday lives, including how we choose mates and why we love rhythm so much, and provides a new perspective on addictive behaviors. Finally, chapter 12 summarizes this material and considers the open questions that await answers from future research.

—Milan Kundera,
Immortality

—Edward O. Wilson,
Consilience

 

 

 

I
n most families there is nothing more exciting than the appearance of a new baby. In ours, the latest addition is my little niece Kathleen, who now in her fourteenth month can do so many amazing things, most of which we take for granted but are really miracles of development. A few months ago she joined the ranks of fellow bipeds and meanders about the house awkwardly, resembling a slightly inebriated little sailor making her way home after last call. She can recognize objects as being unique and distinct from others, no longer labeling everything uniformly as “daht.” And she has an amazingly complex palate of emotional expressions, the full range of which, I have come to realize, can be displayed with little or no notice. But this is just the beginning.

It’s been clear for many weeks that Kathleen can understand far more than she is able to verbalize. Sitting next to her at dinner the other night, I noticed she was trying to catch a balloon tied to the back of her chair. “Do you want me to get that for you, sweetie?” I asked. And then, all of a sudden, it happened—she said, “Yeah . . .” At last, contact! There was a real person inside that little body. Our brief exchange didn’t grab the interest of those around us, but I was astonished by the unexpected exactness of her answer. For the first time, I truly felt we had made a connection.

Later that evening while talking with a friend about my dinner conversation, I tried to explain why I was so taken aback by my niece. Surely it is to be expected that she’ll begin to talk sooner or later, but my surprise arose from two levels of awareness. On the first level, it’s staggering to think of the mechanistic and computational achievement it is to extract meaning from mere acoustic energy—sound waves thrust in your direction from the peculiar manner in which people modulate their breath as they exhale. The biological and psychological capacities that support the many processes in between auditory sensation and language interpretation can (and do) fill volumes in university libraries. Then there is the other side, language production. After Kathleen has interpreted my question and decided on an answer, she must mold her young articulators into the correct spatial arrangement, which varies over time, to create the proper sound waves that will have meaning for me, the listener. And finally, there is all that fancy neural processing in between language interpretation and production that is made evident when we realize that Kathleen’s answer does not result from some simple stimulus-response pairing, a monosynaptic reflex, or a bit of classical conditioning. Rather, a conscious, self-referential decision was made.

In his book
The Language Instinct
, cognitive scientist Steven Pinker marvels at this peculiar trick humans have evolved for communication:

 

He makes the important point that the miracle of language is not just in its mechanics—sound waves bouncing off a cochlear, larynx, and pharyngeal openings constricted just so—but in the functional properties that emerge with its usage, namely the exchange of information that may come in any number of forms, such as those relating to nature, technology, social identity, physical health, emotions, and so on.

This brings me to the second reason I was so surprised by Kathleen. When she answered, “yeah,” I was impressed by her response on an intellectual level, yet at the same time, I felt an inexplicably strong emotional reaction, an attachment that formed instantly with this single syllable. I had heard her say words before, so it was not the mere occurrence of recognizable speech, but rather the context of the social connection that bound us that was so engaging. Just as the emergence of language has been shaped, in both the species and the individual, by the competitive forces of natural selection, so too has the appearance of emotions such as pleasure. The manner in which pleasure drives our biological need for social attachment and communication is the subject of this chapter, and it is an amazing story.

Ask an archaeologist what factors gave
Homo sapiens
the competitive edge over our neighbors—
Homo erectus
in Asia and Neanderthals in Europe—and they will likely describe the impressive transition from Oldowan stone tool use found at sites dating 2 million to 1.5 million years ago to the more sophisticated Levallois flake technology for making sharp blades.They will further comment on the explosion in variety and specificity of tools for different functions that appear in the archaeological record: elegant wood-carved spears used for hunting game; blades shaped into projectile points, end scrapers, chisels, and burins, all custom-made to match a particular task; and tools born from bone such as awls and needles. Ask anthropologists the same question and they will use the same archaeological data to remind us that earlier hominids tended to segregate their daily lives into different locations according to task.Tools were constructed in one location, food preparation in another, and so forth.
Homo sapiens
, on the other hand, are believed to have used a centralized location where all of these activities were performed together, providing an integrative and highly social aspect to everyday life.

But we are left with this daunting question:Why did this shift in social behavior occur? Put simply, why did our ancestors enter the “cognitive niche”? The survival of typical
Homo sapiens
depended critically on the possession of very basic factual knowledge and skilled techniques for managing their place in the habitat. They had to be able to locate food and know how to extract and prepare it for consumption. They had to learn where their predators were and how to avoid or defend against them. They needed to be familiar with the terrain and, at the very least, possess rudimentary navigation skills. The list goes on and on—just for basic survival. Such increasingly complicated knowledge can most effectively be learned in the context of a social community. In the words of British psychologist Nicholas Humphrey, such a community “provides both a medium for the cultural transmission of information and a protective environment in which individual learning can occur.” In this sense, the primary role of intelligence in higher primates is not to produce great works of art or advance scientific achievement, but simply to hold society together.

Once a species begins on the path toward socialization, it is as if they were thrown on an evolutionary treadmill, and there is no going back.The emergence of social interactions ultimately leads to ever-increasingly complex social behaviors, social emotions, and group conduct that in turn develop a need for yet more complex social skills. This process is known in evolutionary biology as a “ratchet effect,” somewhat akin to a gear that is only capable of moving in a single direction. The limiting factor, of course, is determined by the extent to which the adaptive consequences of social behavior outweigh its burden and eventual cost on successful reproduction. Those individuals who place too great an emphasis on socialization while neglecting other subsistence factors will have a reduced chance of survival into reproductive age and attracting a suitable mate.