Zoobiquity (16 page)

These animal examples also challenge anyone who would stigmatize addicts or moralize about the disease. What you might see as a personal failing in your no-account uncle who ruins every Thanksgiving with his drunken antics is not a uniquely human impulse. Uncle Bill is not alone in the animal kingdom in seeking and responding to chemical rewards. Maybe knowing that won’t make the annual get-together any more pleasant—or his life any easier. But the fact remains that driving his addiction is a chemical reward system shared by other animals, from worms to primates, which has been in existence for millions of years. True, Uncle Bill can choose between a trip to the liquor store and a trip to his AA meeting. But if a fruit fly had the same option, it, too, might sometimes take a rain check on sour coffee in a Styrofoam cup in favor of a warm, soothing hit of ethanol.

Jaak Panksepp never expected to make his name by tickling rats. He’d planned to be an architect or an electrical engineer or, at one point, inspired by his University of Pittsburgh freshman classmate John Irving, a writer. But an internship at a mental hospital when he was an undergraduate set him on a different path. Seeing how the patients there required a wide range of treatments, from short-term stays to padded cells, made him want to understand, he says, “
how the human mind, especially emotions, could become so imbalanced as to wreak seemingly endless havoc upon one’s ability to live a happy life.” And so he became a psychologist and, later, a neuroscientist. He now holds a position that gives him a unique vantage point on how the brains of many species work. As the Baily Endowed Chair of Animal Well-Being Science in Washington State University’s College of Veterinary Medicine, Panksepp brings his expertise in human emotional systems to a department devoted to the health of nonhuman animals.

Panksepp specializes in what goes on chemically and electrically in the brains of mammals when they play, mate, and fight, or separate and reconnect. And he is convinced that human addictive behaviors stem from ancient parts of our brains that are shared across species.

Rat tickling came in the mid-1990s, after Panksepp had spent several decades studying play urges in rodents. Using an audio device that measured the ultrasonic vocalizations of bats, Panksepp had discovered that rats make two very different sounds when they’re playing. Happily engaged rats emit abundant high-pitched chirps at about fifty kilohertz—much higher than we can hear with the naked ear. To Panksepp it sounded happy, a bit like childhood giggling and laughter. He wondered if the animals would make this sound under other circumstances. One morning, he took a rat accustomed to being held by humans, gently rolled it onto its back, and tickled its belly and armpits. Instantly he heard it: fifty kilohertz vocalizing. He tried another rat. Same thing. Rat after rat, eventually over many years and in many different labs, vocalized at fifty kilohertz when they were tickled in this way.

Panksepp and others found that rats make this “happy” sound in several other specific situations. When they’re copulating. When they’re about to get food. When a lactating mother is reunited with her offspring. But most especially when two friendly rats are playing with each other.

Their other major vocalization registers at a much lower—but still inaudible to human ears—twenty-two kilohertz. Rats make this very different sound when they’re alarmed, anticipating a scary situation, when they’re fighting, and especially when they’ve been defeated in a skirmish. Although not a measure of physical pain, it apparently does reflect psychological distress or psychic pain. Baby rats make a version of it when they’re abandoned by or isolated from the warmth of their mothers.

Panksepp says that when you run these sounds through a machine that translates them to a frequency we can hear, the high-pitched notes are roughly analogous to human laughter. The low-pitched calls sound like human moaning. He’s found rats make the higher, chirping sound when they’re anticipating receiving drugs they desire. They utter the lower, moaning sound when deprived of the drugs and experiencing withdrawal.

Panksepp thinks it’s no accident that rats emit the same sound when
they’re in psychic pain and when they’re denied a drug they crave. “Pain” is a word that came up again and again in my interviews with human addicts and the doctors who treat them. Overwhelmingly, addicts report that they need their substances to “dull the pain,” “make the pain go away,” or “make the suffering disappear.”

Rarely do they mean literal, physical pain (although many addictions, especially to opioids, begin with a prescription for relief of bodily pain). The pain that addicts describe is more of an ineffable internal ache—an emotional throbbing or social tenderness.

Panksepp is not the first to wonder whether other animals experience life in a way that could be called “emotionally” painful. This fundamental question has puzzled thinkers for generations: Do animals feel things the way we do?

Charles Darwin tackled the issue in his 1872 book
The Expression of the Emotions in Man and Animals
. Trying to extend his principles of evolution beyond anatomy, he argued that natural selection could be applied to emotion and behavior. The idea didn’t catch on. Darwin was up against two centuries of René Descartes’s insistence on a dichotomy between body and soul. For Cartesians, only humans—specifically, men—possessed a soul, which was also the seat of intelligence. Having neither soul nor emotions, animals existed in a purely physical realm. Instead of “I think, therefore I am,” Cartesians believed that for animals it was more like “I can’t think, therefore I can’t feel.”

Without the tools to track—or even define—emotions in nonhuman species, the behaviorists of the early twentieth century, like J. B. Watson and B. F. Skinner, were obliged to infer what an animal might be experiencing solely by observing its behavior. Here the differences between animals and humans really did get in the way. The facial muscles of most animals don’t react in ways that clearly communicate pain to a human observer.
Most animals don’t vocalize when they’re hurt (at least not at frequencies we can hear)—possibly as a self-protective strategy against attracting predators. Many withdraw instead of seeking help. So different are these responses that they supported the behaviorists’ idea that animals don’t, or can’t, perceive physical pain.

Because they couldn’t see what was going on inside the cranium, the behaviorists concluded that animal conduct occurred without awareness. If a creature didn’t “know” it was in pain, then it couldn’t possibly
feel pain. Only human brains (and perhaps some other highly developed simian brains), they believed, functioned at a level of cognition high enough to process the unpleasant sensations of pain. Although the behaviorists were trying to reconcile body and mind, they succeeded only in further splitting them. Animals went from being soulless physical entities to boring biological machines. Remarkably, the notion that human consciousness was a prerequisite for feeling pain persisted into the last part of the twentieth century.
^‖

And in some cases tragically, this belief was applied to another group of beings who can’t use words to describe their experiences: human infants. The conventional medical wisdom
until the mid-1980s
held that newborns’ neurological networks were immature and thus subfunctional. The prevailing doctrine was that babies “couldn’t feel” pain the way older humans do.
^a

Although this view persisted for an uncomfortably long time, pain management is now a priority in both veterinary medicine and human medicine—including, thank goodness, pediatrics.

Advanced brain imaging and other technologies are emerging that allow us to directly study the brain’s emotional systems. The techniques are providing evidence for Darwin’s view that emotions, like physical structures, have evolved. They are subject to natural selection based on their fitness benefit to individuals. And the reason is pretty simple. What
we call “feelings” or “emotions” are not airy, intangible thought-vapors that emanate, auralike, from our brains. Emotions have a biological basis. They arise from the interplay of nerves and chemicals in the brain. And like other biological traits, they can be retained or rejected by natural selection.

Of course,
how an animal experiences the world cannot be fully known to a human being. Some scientists, including Joseph LeDoux, an author and neuroscientist at New York University, object to using the word “emotion” when describing the interior world of animals. LeDoux coined the term “survival circuits” to describe the hardwired brain systems that drive animals to defend themselves and promote their well-being.

Randolph Nesse, a University of Michigan psychiatrist and a leader of the growing field of evolutionary medicine, put it this way in a paper in
Science
: “
Emotions … shaped by natural selection … adjust physiological and behavioral responses to take advantage of opportunities and to cope with threats that have recurred over the course of evolution.… Emotions influence behavior and, ultimately, fitness.” Nesse’s view echoes that of E. O. Wilson, who wrote, controversially at the time, “
Love joins hate; aggression, fear; expansiveness, withdrawal … in blends designed not to promote the happiness of the individual but to favor the maximum transmission of the controlling genes.”

Whether or not we use the word “emotion” to describe it, animals seem to be rewarded with pleasurable, positive sensations for important life-sustaining undertakings. These are activities such as finding food, approaching mates, escaping to a hideout, outrunning a predator, and interacting with its kin and peers. The joyful pleasure a young human or animal feels upon reuniting with a caretaking parent encourages bonding, for example. Pleasure rewards behaviors that help us survive.

Conversely, depression, fear, grief, and isolation, among other negative sensations, indicate to an animal that it’s in a survival-threatening situation. Anxiety makes us careful. Fear keeps us out of harm’s way. Imagine the trouble you’d be in if you didn’t feel anxious and fearful when encountering a rattlesnake on a hiking trail or a masked gunman at an ATM.

And there is one thing that creates, controls, and shapes these extremely important feelings: tiny hits of addictive chemicals stashed in microscopic pouches (called vesicles) in our brains.

It’s as though we’re all born with an internal Pyxis 3500 machine that opens specific drawers in response to our unique genetic “thumbprints” and behavioral “codes.” Our personal chemical-dispensing apparatus is stocked with tiny capsules of natural narcotics: time-melting opioids, reality-revving dopamine, boundary-softening oxytocin, appetite-enhancing cannabinoids, and many more—some of which haven’t even yet been identified.

Gaining access to one’s personal, intracranial lockbox may be one of the most potent motivators in animals, including us. But instead of entering a number, an animal must perform a behavior to release the substances. Behaviors are the codes. Do something that evolution has favored, and you get a hit. Don’t do it, and you don’t get your fix.

Foraging. Stalking prey. Hoarding food. Searching for and finding a desirable mate. Nest building. These are all examples of activities that greatly enhance an animal’s chances of survival, or what biologists call fitness. Pleasant sensations of anticipation and excitement—born in the brain’s neural circuitry and chemistry—encourage initiative, risk, curiosity, and discovery in animals.

We humans have a similar suite of life-sustaining activities. We just call them by different names: Shopping. Accumulating wealth. Dating. House hunting. Interior decorating. Cooking.

Indeed, when these activities have been studied in humans and other animals, they are associated with rises in the release of certain chemicals, mostly dopamine and other similar stimulating compounds. Nesse notes that “
from slugs to primates,” dopamine mediates the search for and consumption of food. Ancient dopaminergic systems have been found in fruit flies and honeybees, suggesting that similar reward experiences may be at play in their behavior. Bees have increased levels of octopamine (their version of dopamine) when they are foraging. Tellingly, their drive to find food appears to come not from personal hunger but rather from a desire for the reward.

Finding safety can also trigger these chemical rewards. Imagine the tremendous relief you felt when the biopsy came back benign, or when the creepy person behind you on the sidewalk turned down another street. That flood of relief is actually a chemical dump within your brain.

Opioid receptors and pathways (the same pathways used by heroin, morphine, and other narcotics) have been found in jawed vertebrates that lived 450 million years ago—well before mammals came on the scene. That
means that, from barracudas to wallabies, Seeing Eye dogs to homeless heroin addicts, animals have an ancient and intimate response to opiates.

Researchers working with Panksepp have found that opiates regulate separation and distress calls in dogs, guinea pigs, and domestic chicks. His colleagues have also found that when dogs wag their tails and lick each other’s or their owners’ faces, that behavior, too, is modulated by opioids. Opioids play a role in early suckling behavior in rats. And the proximity of offspring has been shown to trigger a hit of pleasurable chemical reward in the brains of rat mothers.

Besides opiates and dopamine, many other chemicals work constantly in our bodies and brains. Cannabinoids, oxytocin, and glutamate, among others, create a complex system of simultaneous positive and negative sensations. This cacophonous chemical conversation (what Panksepp calls the “
neurochemical jungle of the human brain”) is the basis of emotion—emotion that creates motivation and drives behavior.

Human feelings powerful enough to launch a thousand ships, build the Taj Mahal, or ignite pleasurable melancholy at Mimì and Rodolfo’s parting in act IV of
La Bohème
have emerged from “survival circuits” (to use LeDoux’s term) that we share with other animals. In other words, our emotions exist as they do today because their building blocks helped our animal ancestors survive and reproduce.