The Pleasure Instinct: Why We Crave Adventure, Chocolate, Pheromones, and Music (29 page)

This book entertains a third point of view that is distinctly different from those of the hedonists, who equate pleasure with happiness, and the modern-day stoics, who are guided by varying belief systems, yet at their core share an uneasy truce with pleasure. All of our emotions, including the experience of pleasure, have been shaped by natural selection to cope with challenges and opportunities that have recurred over the course of hominid evolution. In this context, pleasure may point us down a particular path, but it is not the final destination.

From a strict evolutionary perspective, the story of pleasure is often summed up in a few pages as one dealing almost exclusively with sexual behavior and reproduction. Sex has been linked to pleasure through natural selection to maximize genetic propagation—end of discussion. As we’ve seen, however, the role of pleasure in human evolution and development is far more complicated and interesting.

The modern hedonic palate is amazingly diverse and shaped by a host of personality and cultural factors. The feeling of pleasure can be elicited by a wide range of experiences, each involving disparate sensory systems. Likewise, the expression of pleasure in terms of overt behaviors or verbal descriptions varies considerably within different contexts and cultural norms. Although each of us has unique likes and dislikes, there is a common core of sensations that the vast majority of humans label as pleasurable. Our preference for these core sensations arose though natural selection to ensure that we experience key sensory events during our early years that are
required
for normal brain development. This does not mean that we are all destined to be attracted to exactly the same phenomena, but rather to the same general classes of stimulus features. To really understand the choices we make in contemporary life, it is critically important to consider the modern problem of how cultural influences interplay with nature’s program of sensory and behavioral preferences.

Addiction, for example, is certainly not a modern problem.There are historical accounts of addiction to everything from chocolate to sex to war. As we have seen, at its root addiction is a biological phenomenon regulated by the brain circuitry that is involved in reward and motivated behaviors (see chapter 11). Clearly, however, cultural norms have a way of insinuating themselves into the biological mechanisms that control these behaviors.

Modern addiction—whether we are talking about heroin, alcohol, nicotine, over-the-counter drugs, gambling, or your favorite soap opera—is often said to be facilitated by two key elements: the ease with which a drug or experience is acquired, and the rate at which it activates the central nervous system. Smoking, for instance, is highly addictive because tobacco products are readily available, and nicotine rapidly activates the dopaminergic brain systems we discussed in chapter 11. A third element that should be considered is whether the focus of an addiction involves more than one hedonic preference. Many addictions involve compounded stimuli. One can think of these as complex experiences that are comprised of two or more fundamental hedonic preferences. Smoking and alcohol are both addictive in themselves, but are far more addictive when combined together. Indeed, becoming addicted to either smoking or drinking alcohol markedly increases the odds of becoming addicted to the other. This makes intuitive sense, since both forms of stimulation are activating the same brain reward mechanisms.

As we have seen, nature’s list of hedonic preferences is long and taps into every sensory domain. This provides an enormous palate of sensory experiences that can be combined in culturally acceptable ways to form compounded stimuli. Toddlers are not terribly burdened by cultural norms, so the impact of compounded stimuli is most apparent in the things that grab their attention. The appeal of shows such as
Barney and Friends
and
The Teletubbies
is easily understood when considered from this perspective. Both shows deliver daily doses of compounded stimuli that are sharply tuned to match several of the hedonic preferences we have been discussing. Included among these are stimuli formed by sharp contrasts, bright primary colors, pronounced lateral symmetry, repetitive sounds and movements, and exaggerated intonation and facial images.

Adults are not exempt from the lure of compounded stimuli, but their attraction to these experiences is shaped significantly by cultural expectations and previous life events. Memory and associative learning link everyday stimuli to primary reinforcers, and this process plays a large role in determining what an individual finds pleasurable.

In the past three chapters we saw how the pleasure instinct crafts time-sensitive developmental preferences for certain types of stimuli that, in turn, can emerge as receiver biases in adults. There is probably no better place to look for examples of this process than the modern consumer world. In 1957, Vance Packard published his classic book
The Hidden Persuaders
. This was the first broadly read account of how the advertising community was taking advantage of discoveries in a number of scientific disciplines to tap into subconscious processes for the benefit of product positioning.

Packard’s book focused on psychological processes that might be important for making a product appear more desirable to a targeted consumer. Receiver biases may also make certain products seem more appealing; however, the mechanism can be clearly linked to developmental preferences forged by natural selection and, in some cases, magnified by sexual selection.

Symmetry, proportion, and rhythm are particularly good examples of receiver biases that clearly have a home in the advertiser’s toolbox. Our innate preference for these features has been studied by marketing scientists for decades and applied to everyday commercials. For instance, symmetry is a particularly ubiquitous feature of design logos for consumer products ranging from automobiles to home electronics, where the implicit message is one of—you guessed it—fitness. Indeed, virtually every major manufacturer of consumer goods today employs or consults sensory scientists to optimally align the aesthetic features of a product with Gestalt forms that are innately pleasing. These scientists spend a great deal of time getting customer feedback on potential product design, packaging materials, promotional displays, advertising placement, and so forth. These days I can no longer go into a department store and simply shop. Instead, I find myself counting the many ways I am subtly manipulated by the growing armamentarium of advertising/marketing devices supplied by modern sensory science, evolutionary biology, and neuroscience.

 

 

In chapter 3 we discussed the pioneering work of psychologists James Olds and Peter Milner, who in 1954 were the first to discover the so-called pleasure centers of the brain. Although modern brain theorists are still grappling with what is actually experienced when these sites are stimulated, an important finding is that a fairly restricted and well-defined set of circuits has been implicated again and again in literally thousands of studies. There are many ways to promote activation of these circuits via different sensory domains and experiences. Similarly, once these circuits have been activated, they may signal a diverse number of other brain regions that are responsible for the appropriate behavioral response.

Today it is unclear whether we should call the limbic circuitry involved in reward and motivation “pleasure centers.” Olds and Milner stayed away from this terminology initially, but early theorists simply could not resist. Normal functioning of this limbic circuitry is implicated in several processes that seem to be related to pleasure. These include reinforcement learning through reward, consummatory behaviors such as eating food and mating, and appetitive or motivated behaviors such as those leading up to the point of actually receiving the reward.

The portions of the brain where this circuitry resides are subcortical structures that have existed at least as long as the birth of mammals. The evolution of primates is a story that in many ways began with the limbic system and the behaviors/functions it supports. Nature rarely reinvents itself. The general pattern of brain circuitry one sees in limbic structures such as the hippocampus (for example, recurrent excitatory synapses modulated by feed-forward inhibition) forms the basis for much of what is seen in neocortical structures. The gradual emergence of the primate line was accompanied by neocortical development that was based on mammalian limbic circuitry.

This evolutionary sequence is echoed in the embryonic growth of humans. Each milestone of brain development that is traversed by the growing child is a reprise of our evolutionary past. Limbic structures give rise to neocortical structures, and, most importantly,
limbic functions give rise to neocortical functions
. The basic emotions, including pleasure, laid the foundation for the gradual emergence of higher cognitive processes unique to human primates (for example, language and musicality). Parents see this process unfold daily as limbic functions such as finding pleasure in primary colors, faces, symmetry, repetitive movements, and certain sounds direct babies and toddlers toward the necessary experiences that will guide the continual development of more complex functions that require a healthy neocortex.

With only twenty-five thousand or so genes constituting the entire human genome, nature is forced to conserve at every step. Developmental bootstrapping is an elegant compromise that engenders the individual with a rapidly growing brain and a built-in desire to seek experiences that will fine-tune this circuitry. This process has quite a bit of freedom and flexibility. It’s somewhat akin to a robotics engineer getting the basic wiring and simple functioning working and then letting the machine do the rest of the programming based on a few simple rules. The first rule is that certain classes of stimuli must be experienced during development to ensure that the programming is continued. The second rule is that the particular stimuli the robot encounters in these general classes will fine-tune the machine to life in a specific environment.

Machines are generally not designed this way, of course, but biological organisms possess a delicate balance of preprogrammed growth that depends on experiential refinement. This freedom and flexibility has its costs. Addiction is the most obvious example of how bootstrapping as a general developmental process can lead to potential problems. Compounded stimuli are not just found in modern environments, but the ease with which so many different hedonic preferences can be satisfied at a moment’s notice is clearly an oddity of contemporary life. In the twenty-first century we have extraordinary technological means to quench our thirst for pleasure, and the potency of addiction will increase when our drug of choice is mixed with other hedonic preferences.

These ideas and findings suggest a novel treatment strategy for dealing with addiction in the broadest sense. Focusing solely on the primary point of addiction (for example, smoking or consuming alcohol) will generally be less effective than identifying all of the hedonic preferences associated with the behavior and treating the compounded stimuli as a whole. This perspective suggests, for example, that treatment for alcohol addiction should also include a therapeutic means to reduce smoking (if applicable) and curtail any increases in sugar consumption. Such a scenario is typically not part of alcohol treatment programs, many of which allow (or even encourage) substituting one addictive substance for another—sweets in place of nicotine, caffeine in place of tobacco, and so forth. People often find it easier to treat addiction through substitution.You probably know at least one person who quit smoking or drinking alcohol, only to increase another behavior that is equally addictive.This happens with great frequency, since all hedonic preferences—regardless of the sensory domain (for example, taste, touch, vision, etc.)—stimulate the same brain circuitry involved in reward and motivation. Activity in this circuitry is regulated by a number of additional systems, with the aim of keeping it within a range of acceptable levels (allostasis).

 

 

Addiction is really just the tip of the iceberg. Understanding the role of pleasure in the modern context requires stretching back in historical time and considering its function in the evolution of our species. It also requires thinking about the role of pleasure in human brain development—from embryo through the toddler stages, into adolescence, and then adulthood. Understanding how pleasure influences our behavior is critical for parents who want to make intelligent choices about the growth environments they provide for their children. Yes, it is obvious that children need stimulation to develop along a normal trajectory, but not all stimuli are created equal. There are clearly optimal forms of stimulation that parents should bring into their children’s world. The pleasure instinct will do the rest by causing the child to repeatedly engage in play with objects that have these features.

There is, of course, a tremendous benefit for adults as well. Pleasure has varied roles in our modern lives, many of which are influenced by its original developmental purpose. Understanding the original role of pleasure helps to frame the modern experience by revealing key features of our lives that it impacts, ranging from addiction to the influence of advertising on consumerism. Hedonic preferences do not simply go away as we grow older. While it is true that they become increasingly shaped by our experiences and cultural norms with age, they are still with us, anchored beneath all the top layers. There is no doubt that brain development hits its zenith in our early years, but it is a continual process throughout the entire life span. Old neurons die, new neurons are born. Since brain development slows significantly after adolescence, the role of pleasure in guiding this growth becomes less central. Nevertheless, the pleasure derived from experiencing the many forms of developmentally important sensations persists—a common gift shared by us all, yet flavored by our unique life events and conditions.