The Science of Happiness

by Chris Woodford. Last updated: November 8, 2022.

It's all in the mind—a suggestion that mental illnesses are more of a pushover than physical ones—has long been a favorite way to shrink our troubles down to size. If there is any truth in this, one implication might be that happiness is "all in the mind" too. This begs an important question: is there some province of the gray matter where we could bang a stake labeled "Happiness," some well-delineated region of the cerebral cortex, perhaps, that acts as the engine of our joys and delights?

Given that the human brain has evolved in unplanned, bottom-up fashion from the less sophisticated precursors of fish, amphibians, reptiles, and rodents over many millions of years, the reality is unlikely to be so simple: if no-one designed the brain to be happy from the "top down", happiness must have evolved from the "bottom up" to serve some specific purpose [1]. But is the "happiness" we struggle toward in our everyday lives the same thing as the "happiness" that occurs inside our brains? And does one necessarily create the other? Such questions have moved center stage for neuroscientists who are now probing the mechanisms by which our brains turn genetic predisposition, past experience, and everyday events into powerful emotions like anger and fear, depression and joy. Their quest—which uses science to probe the mental mysteries of emotion—is slowly revealing the secrets of the happy brain.

Photo: Can science put a smile on your face?

Modularity of mind: a brief history

Evolution thrives on chance. Yet the brain, the most complex and arguably the most important organ in the human body, is organized in anything but a haphazard fashion. Far from being a cluttered "attic", jammed with random memories and a lifetime of chaotic experience, the brain is a self-organizing, general-purpose information processor far more robust and adaptable than any computer. Scientists and laymen are equally fond of likening brains to computers and vice-versa—and the comparison has proved remarkably fruitful for the study of both kinds of thinking machine: a branch of psychology called cognitive science has made enormous leaps in helping us to understand the brain by viewing mental tasks as series of steps not unlike computer programs; meanwhile computer scientists have discovered they can set up and program machines as neural networks, highly interconnected computer systems that "think" in parallel (carrying out many operations simultaneously) much like the human brain is believed to do. The logical conclusion of this work is a gradual blurring of human minds and "artificially intelligent" machines, long forecast by computer scientists such as Ray Kurzweil [2]: in December 2004, neuroscientists hinted at the shape of things to come when they wired a rat's brain to a computer and trained it like a neural network to fly a jet fighter [39].

The idea that the brain is a modular machine whose components have fairly specialized roles is often portrayed as a modern discovery: it is modern brain imaging techniques, for example, that show different regions of the brain "lighting up" [3] when people are asked to think, reason, or remember in different ways. Yet the modularity of mind is actually a much older idea.

Bumps on the skull

Like much of modern medicine, the idea that different parts of the brain do different jobs seems to have cropped up first in an Egyptian manuscript discovered by Edwin Smith in Luxor in 1862, itself generally believed to have been copied from a much older document that dates back to 3000 B.C. The Edwin Smith papyrus, as it has since been known, is generally regarded as the world's first scientific document and contains 48 medical case studies, including this account of how brain damage can lead to specific disorders of bodily functions:

"If thou examinest a man having a smash of his skull , under the skin of his head, while there is nothing at all upon it, thou should'st palpate his wound. Shouldst thou find that there is a swelling protruding on the outside of that smash which is in his skull, while his eye is askew because of it, on the side of him having that injury which is in his skull; (and) he walks shuffling with his sole, on the side of him having the injury which is in his skull..." [4]

Artwork: The Edwin Smith papyrus. Photo by Jeff Dahl courtesy of Wikimedia Commons.

Influential early thinkers like Aristotle (384–322 BC), Galen (the father of western medicine, AD129–c.216), and St Augustine (c. AD 500) supported the idea that the brain's ventricles (large, open cavities inside the brain that are filled with cerebro-spinal fluid) were the seat of higher mental functions such as thinking and reasoning. This view persisted, as medieval science was inclined to do, for many centuries. During the Renaissance, Leonardo da Vinci (1452–1519) and Andreas Vesalius (1514–1564) lifted the lid of the skull to make accurate anatomical sketches of what they found inside. Taking the human body apart and numbering the pieces, not unlike a medieval Haynes manual, Vesalius was illustrating parts of the brain and speculating they were dedicated to different mental functions around 500 years before neuroscientists and brain scanners started doing much the same thing.

Illustration: Lifting the lid on the skull. Historic illustration of brain anatomy c.1543 by Jan Stephan van Calcar, who worked with Andreas Vesalius.

The idea of the modular mind had its apotheosis with the phrenologists, a group of 19th-century scientists who believed the brain was divided into distinct regions, each one specialized in something like memory, language, benevolence, or wisdom, with the whole cerebral territory as neatly demarcated as a map of beef cuts hanging on the wall of a butcher's shop. The phrenologists' plans of the mind embodied much the same pioneer spirit as the conquest of the New World and the "Scramble for Africa": at a time when European explorers were conquering whole new continents, phrenologists were staking similar claims on the brain. For Guinea, the Congo, and Abyssinia, read "Amativeness", "Sublimity", and "Suavity".

Illustration: A phrenological mind map. Picture by Fowler & Strachan c.1842, courtesy of US Library of Congress.

As modern neuroscientists happily concede, the basic principle of phrenology—what they term "localization of function"—was perfectly sound. It is certainly the case that different parts of the brain do different jobs, although there is little to suggest the mental territory divides up quite so cleanly as the phrenologists' insisted or that abstract mental functions like "Hope" or "Parental love" can be meaningfully localized at all. Worse, the phrenologists took their idea to a logical conclusion that seems ridiculous to us now. Everyone's skull has lumps and bumps, for no particular reason, but the phrenologists believed the cranial landscape was shaped by the size of the brain areas inside it. So, if a person's "Combativeness" area was overdeveloped, a large bump might appear just behind and above their ear; feeling a person's head for lumps and bumps could, therefore, be used to diagnose all kinds of mental illnesses and physical ailments... or so the phrenologists led themselves to believe. The inevitable rejection of this quackery, by critics such as Pierre Flourens (1794–1867), eventually led to the demise of the whole notion of localization of brain function in favor of the idea that mental functions were distributed more evenly throughout the brain—an idea known as equipotentiality (because different parts of the brain play an equal part).

There was no brain organ devoted to "Hope" or "Benevolence", but the idea that different parts of the brain might be devoted to more clearly defined functions persisted, notably in the work of Paul Broca (1824–1880) and Carl Wernicke (1848–1904) on the localization of language. In 1885, Broca launched the pop-psychology concept of left-brain/right-brain when he stated, famously: "Nous parlons avec l'hémisphère gauche". Wernicke supported the idea that complex mental activities were carried out by a relatively small number of brain areas dedicated to different tasks and that lesions of a particular brain area would disrupt people's abilities to do those things. An "original and independent mind", Wernicke was also one of the first people to champion the now-fashionable idea that mental illness is essentially a neurological problem [5]. He remained a scientist to his dying day: knocked off his bicycle by a truck, his final words were: "I am perishing of autopsychic disorientation." [6]

You can ring my bell

Photo: Sigmund Freud. Photo courtesy of US Library of Congress.

The concept of the modular mind largely vanished during the first half of the 20th century. Psychiatry was dominated by the sex-obsessed speculations of Sigmund Freud, for whom the dark and spooky attic of the "unconscious" could be probed only in indirect ways, such as through dream reports, hypnosis, and flat-on-the-couch psychoanalysis. Freud's genius was to transform psychology from a descriptive to an explanatory science. But he over-reached himself. Flying in the face of Ockham's razor (a basic principle of science, proposed by 13th-century Franciscan philosopher William of Ockham, that suggests the simplest theory consistent with the facts is generally the best) Freud proposed absurdly elaborate and often quite bizarre sexual explanations for mental illnesses that are now much more plausibly explained by the more prosaic science of brain chemistry. All this is hardly surprising, because as Freud confessed to his friend and confidant Fliess in 1900: "I am actually not a man of science at all... I am nothing but a conquistador by temperament, an adventurer." [7] Although Freud's ideas remain enormously influential in such cultural fields as biography, many psychiatrists now consider it safe to abandon them on the compost pile of history. Edward Shorter, for example, considers Freud "an interruption, a hiatus", albeit one of "enormous consequence":

"In retrospect, Freud's psychoanalysis appears as a pause in the evolution of biological approaches to brain and mind rather than as the culminating event in the history of psychiatry." [8]

Many psychologists were also persuaded to view what happened inside the brain as an irrelevance thanks to the influence of behaviorism, a movement that tried to inject true scientific respectability into psychology and consequently found it necessary to ban such woolly concepts as "mind" and "mental processes" altogether. Strongly associated with the influential American psychologists B.F. Skinner and J.B. Watson, behaviorism was based on experiments like Pavlov's classic finding that dogs can be "conditioned" to salivate when someone rings a bell: if you ring a bell every time you give your dog his dinner, and the dog salivates in anticipation of eating, the dog will eventually learn to salivate even if you ring the bell without serving any food. For behaviorists, every aspect of animal behavior—from the way infants become attached to their mothers to the reasons behind deviant human behavior, such as football hooliganism—can be explained in terms of "stimulus" and "response". How the brain came to link different patterns of stimulus and response (its inputs and outputs, if you prefer) was not relevant: many drivers have little idea how their car engines work—they would never dream to lift the bonnet—and behaviorists had a similar attitude to mental processes. There was, according to the behaviorists, no way of knowing what went on in the "black box" of the brain: you could not trust people to comment on their own thoughts and feelings (introspection, according to the behaviorists, was notoriously unreliable) and you certainly couldn't lift the skull and see what was happening inside (though, many years later, brain imaging techniques would allow psychologists to do just that).

Behaviorism dominated psychological thinking from the 1910s until the 1960s when a new way of thinking about thinking—cognitive psychology—started to emerge, much to Skinner's disgust. Forced to nominate a single, 20th-century invention that changed the world more than any other, what would you pick? Some people would opt for the affordable motor-car (although the internal combustion engine was actually invented just before the turn of the century); others might plump for radio (which played a central role in the rise of Nazism) or television. Many would settle on the computer, an information-processing machine whose influence on our understanding of the brain has been just as great as its influence in the fields of work, education, or entertainment.

Computers in the mind

Cognitive psychology relies on computer-inspired models to illuminate the brain: where behaviorists assumed the brain was a "black box"—and a Pandora's box at that—cognitive psychologists have filled the dark space with flowchart-style squares, linked with arrows, and tried to see where it gets them. Mental functions, such as memory, thinking and reasoning, and action (the cognitive control of our bodily movements), are understood in terms of sequential processes that happen with just as much as logic as computer programs but also, given the complexity of the brain, somewhat more human fallibility. Ulric Neisser famously charicatured this approach in his 1976 book Cognition and Reality [9]:

No-one has ever gone so far as to suggest the brain actually is a computer; cognitive psychology has always been a heuristic (a kind of "what-if?" scientific metaphor) designed to help science move forward. But having established that something like human memory (to cite just one example) has a number of quite distinct components (separate short-term or "working" memory stores for the things we hear and see), the temptation, nevertheless, has been to try to find where those components are actually located in the brain—to ground the computer metaphor of cognitive psychology in real, living gray matter.

By itself, cognitive psychology could never have achieved this. As the behaviorists realized decades before, there are any number of ways that the "black box:" might be wired up to produce a particular response from a given stimulus: cars are all designed to turn fuel into motion, but piston engines, diesel engines, rotary engines, and even electrically powered fuel cells all do that job in more or less different ways. How, then, to bridge the gap between theoretical models of how our minds work and the brains—once memorably described as being "like two fistfuls of porridge"—that actually do the job?

The solution has come from the brain sciences, a closely linked ensemble of neurological disciplines that study different aspects of the brain's workings in somewhat different ways. Neuroanatomy, for example, focuses on the structure of the brain; it can be studied by dissecting the brains of animals or people who have died or by looking at brain scans of living people. Neurochemistry looks at the chemical messengers (neurotransmitters) that carry signals between brain cells, around fairly well-defined "circuits". Think of a science, put the word "neuro" in front of it, and you just might find a new way of shedding light on the brain.

One of the most illuminating of the neurological sciences, neuropsychology, studies patients unlucky enough to have suffered "lesions" (relatively localized brain damage caused by strokes, brain tumors, and head injuries) and tries to find out what kinds of things those people can no longer do. If they suffered lesions in a particular part of their brain and can no longer recognize people's faces, for example, but they can still perceive and recognize other objects quite clearly, that suggests the damaged part of the brain might have something to do with face recognition. Since the mid-1980s, cognitive psychologists and neuropsychologists have worked together increasingly closely. Cognitive psychologists have refined their flowchart-process models of things like memory and language processing partly by taking account of neuropsychological case studies: our theories of the various different kinds of dyslexia (the inability to process written language in the "normal" way) owe much to research of this kind. Similarly, like pioneer zoologists seeking out the snark, neuropsychologists have actively tried to find patients with fairly specific loss (what they term "selective impairment" or "deficits") of certain mental abilities, such as the components of memory. Thus, neuropsychologists confirmed the long-supposed distinction between short-term and long-term memory by finding two quite different types of amnesic patient, some of whom could remember only very recent events for a short time (selective loss of long-term memory), while others could remember only events in the distant past and had no ability to store recent events (selective loss of short-term memory). Inevitably, cognitive psychology and neuropsychology have converged in a field known as cognitive neuropsychology.

It has taken cognitive neuropsychology—and the other neurological sciences—some time to arrive where the phrenologists started. The basic conclusion is much the same: the mind is modular and different parts of the brain do indeed have specialized functions. Psychologists have long known, for example, that the left hemisphere of the brain has a greater role in processing language than the right hemisphere. They also know that visual perception happens in the visual cortex, part of the occipital lobe, a region about two thirds of the way towards the back of each hemisphere. Some mental functions have been localized in the brain with very great accuracy: face recognition (one of our most important survival skills) is now believed to take place a very specific part of the visual cortex.

Cognitive science has often been described as a "new science of the mind", but as Joseph LeDoux powerfully argues, no science of the mind could be complete without an understanding of emotions:

"...cognitive science is really a science of only a part of the mind, the part having to do with thinking, reasoning, and intellect. It leaves emotions out. And minds without emotions are not really minds at all. They are souls on ice—cold, lifeless creatures devoid of any desires, fears, sorrows, pains, or pleasures." [10]

Where, then, does emotion fit in?

High on emotion?

Psychologists have identified some of the pieces of cognition and worked out where in the brain's jigsaw puzzle they fit. But it's early days still and popular perception of neuropsychology has long been wide of the mark. The concept of "left-brain" (cold, rational, linguistic) and "right brain" (emotional, creative, visual)—epitomized by a bestselling, self-help art book whose title exhorts people to Draw on the Right Side of Your Brain—is risibly simplistic. The brain may be divided into two hemispheres, presumably an evolutionary adaptation that increases our chances of survival after a head injury of some sort, but our minds are not so neatly parceled. Even the phrenologists would have drawn the line (metaphorically, this time) at the idea of a brain so crudely bisected into "Rationality" and "Creativity".

It's one thing to try to localize a fairly well-defined cognitive function, such as face recognition, in the cerebral cortex. It's something else entirely to ask how the brain handles a much more general collection of cognitive behaviors that might loosely be described as "creativity". And the situation is even more complex when we turn to emotions. Unlike "higher" mental processes such as consciousness, which many scientists consider we do not share with animals, emotions are much older (in evolutionary terms) forms of behavior that humans and other creatures do have in common: think of "angry" snakes and "worried" sheep.

Photo: Descending into madness: Edwin Forrest as King Lear, courtesy of US Library of Congress.

Another complication is that we tend to understand emotions from a largely emotional perspective: historically, poets, storytellers, musicians, and actors have done more to illuminate emotions than scientists. Shakespeare's portrayal of Lear's descent into madness, written c.1605, arguably remains a more relevant and insightful account of mental collapse than anything Freud wrote three hundred years later:

Who alone suffers, suffers most i'the mind,
Leaving free things and happy shows behind [12].

Science is still popularly perceived as cold, logical, rational, and antithetical to the emotions. Scientists have no feelings, therefore science can neither reflect the dazzling light of heaven nor the dark damnation of hell.

Science and art pound different roads. Art's duty is to parade and provoke while science strives to explore and explain. Science can be dramatic though its job, unlike that of art, is not to dramatize. From a scientific perspective, talking about "the emotions" is about as helpful as talking about "the gods" or "the muses": there is no logical reason to believe that one emotion has anything in common with any other emotion, in terms of how or where it arises in the brain. Why should we believe that the brain mechanisms of happiness have anything to do with those of anger or fear? Why should we even, necessarily, believe that the same mechanisms that underlie one emotion underlie the opposite emotion: it does not automatically follow that depression is a gear that throws the engine of happiness into reverse (although there is some evidence to suggest this). If we cannot even clearly define "emotions" or spell out what differentiates one from another, can we hope to understand how emotions arise in the brain? Is it really possible to take a brain apart and point to parts that make us happy or sad? Perhaps surprisingly, the answer seems to be "yes".

The medical model of mental illness

Understanding how and where emotions are processed in the brain is a tougher problem than understanding cognitive functions like memory or language processing. As we have already considered, higher brain functions like memory, based on the logical processing of information, lend themselves to the computational approach of cognitive science. There is nothing to suggest that emotions can be tackled in quite the same way. Computers do not (yet) have emotions, while less highly evolved animals, which lack some of our own higher cognitive functions, may be no less emotional than we are. All this suggests cognitive science might not be quite so illuminating when it comes to the study of human emotion. As Joseph LeDoux argues "To call the study of cognition and emotion cognitive science is to do it a disservice" [11].

Long before the cognitive revolution transformed their way of thinking, psychologists tried to understand emotions using other theoretical frameworks—especially in people who merited treatment because their emotions were out of balance or control. All psychiatry is, in a sense, concerned with treating emotional problems of one kind or another. For much of the 20th century, psychiatry was dominated by psychoanalysis, though other theories eventually elbowed their way in too. Thus depression, one of the most common mental illnesses, can certainly be described in psychoanalytic terms: Freud might conceivably have diagnosed a female patient with post-natal depression as having "penis envy". Equally, depression can be understood with behavioral (or behaviorist) theories. "Learned helplessness", an essentially behavioral theory proposed by Ivy-league psychiatrist turned happiness guru Martin Seligman, suggests people (and animals) become depressed when they learn that, no matter what they do, they cannot make their lives any better—and give up trying as a result. There are chemical theories of depression as well (how else to explain the success of anti-depressant drugs such as Valium and Prozac?). Given the rise of cognitive science over the last 30 years or so, it should come as no surprise that there are also cognitive theories of depression and cognitive (or "talking") treatments: according to these, people become depressed through a pattern of faulty thinking; arresting automatic thoughts and replacing them with more rational ones is the basis of highly effective and empowering treatments for depression such as cognitive behavioral therapy (CBT).

Just as the prevailing wind of psychology favors cognitive neuropsychology and the idea that mental functions can indeed be localized in different parts of the brain, so the medical model of mental illness has gradually come to dominate psychiatry at the expense of psychoanalysis. In the 1960s, it was plausible for such fashionable "anti-psychiatrists" as the American Thomas Szasz to claim mental illness was merely a "myth":

"The belief in mental illness, as something other than man's trouble in getting along with his fellow man, is the proper heir to the belief in demonology and witchcraft. Mental illness thus exists or is 'real' in exactly the same sense in which witches existed or were 'real'." [13]

In similar vein, R.D. Laing (a colorful British antipsychiatrist whose fitting final words, as he died from a heart attack in 1989, were "Doctor? What f****** doctor?" [14]) romanticized schizophrenia as a kind of crazy disaffection not dissimilar to the angst-ridden existential "nausea" of 1950s Left Bank intellectuals—perhaps the only sane response an individual could show to an increasingly mad world. For Laing, schizophrenia could be an ingenious act:

"... The schizophrenic is often playing at being psychotic... A good deal of schizophrenia is simply nonsense, red-herring speech, prolonged filibustering to throw dangerous people off the scent, to create boredom and futility in others. The schizophrenic is often making a fool of himself and the doctor. He is playing at being mad to avoid at all costs the possibility of being held responsible..." [15]

Today, schizophrenia is rightly regarded as a serious, psychotic illness, most likely caused by defective brain chemistry (an imbalance of the neurotransmitter dopamine) that must be swiftly corrected with drugs: malady, not poetry [16]. Laing's ideas—however sympathetic and well-intentioned they may have seemed in the liberal 1960s—are now regarded as somewhere between an interesting intellectual sidetrack (at best) and dangerous medical malpractice (at worst) [17]. Other serious mental illnesses such as depression and bipolar disorder (manic depression) are usually best treated with a combination of psychotherapy and medication; illnesses like this are called "affective disorders" because they involve a disruption of "affect" (a psychiatric term sometimes used interchangeably with mood, but usually involving fluctuations of mood that last only hours or days, not weeks or months). For much of the 20th century, psychiatry was about using elaborate (and sometimes arbitrarily compiled) catalogs of symptoms (such as the American Diagnostic and Statistical Manual, DSM) to establish a diagnosis and then selecting an appropriate treatment; the brain mechanisms underlying such things as depression and schizophrenia merited relatively little attention. The increasing effectiveness of drug treatments has brought not just a shift toward medical models of mental illness but much more consideration of how and where emotions—and emotional disorders—actually happen in the brain. In other words, psychiatry is on a surer scientific footing than it has ever been. And, just like psychology, it is helping us finally to localize emotions in the brain.

Putting emotions in their place

Photo: Can neuroscience explain what makes us feel happy or sad? Did you notice that Mona Lisa's smile is inverted in this picture?

Understanding the neural basis of emotion essentially comes down to two things: breaking an emotional reaction, such as getting angry or feeling afraid, into a logical sequence of steps, and then understanding where and how each of those steps happens inside the brain. William James (1842–1910), brother of the novelist Henry James and one of the founding fathers of psychology at the turn of the 20th century, was also one of the first to attempt an explanation of this kind in 1884. James turned conventional, rational explanations of emotion on their head: he assumed we sense things, react to them instinctively, and then detect our own reactions—and it is the conscious interpretation of the reaction that amounts to the sense of an emotion. In other words, we see the mouse, jump on the chair, and feel scared because we have already reacted [18]. In 1885, Danish physiologist Carl Lange (1834–1900) independently proposed a virtually identical explanation, which is now generally referred to as the James-Lange theory.

Later psychologists and physiologists, notably Walter Cannon (1871–1945) in the 1920s, rejected the James-Lange theory because it could not explain why people felt subtly different emotions in different situations. There was another problem too. If laboratory animals have parts of their cerebral cortex destroyed ("lesioned"), they continue to show emotional responses, like rage, although they appear not to be consciously doing so—something Cannon famously termed "sham rage". Cannon and his colleague Philip Bard systematically lesioned different parts of an animal's brain and observed how its emotional reactions changed. Through studies such as these, Cannon and Bard proposed that the hypothalamus—a peanut-sized structure buried deep beneath the front of the brain or "forebrain"—lay at the heart of a complex emotional circuit. The idea that parts of the brain were specifically dedicated to handling emotion directly contradicted another of William James' suppositions: as far as James was concerned, there were no emotional circuits or components in the brain.

Theories of the emotional brain crystallized between the 1930s and the 1950s, thanks to the work of two other pioneering neuroscientists. Working independently, American neuroanatomists James Papez (1883–1958) and Paul Maclean (1913–) showed how various closely related components at the center of the brain link together to form an elaborate emotional circuit. Apart from the hypothalamus, the other components include the amygdala (a larger structure located behind the hypothalamus), the hippocampus (a seahorse-shaped structure above and slightly behind the amygdala), the thalamus itself (at the center of the forebrain), and the septum (next to the thalamus). They lie deep beneath the convoluted cerebral cortex that most of us tend to think of, when we think of brains at all. Often known as the limbic region, these structures are believed to have evolved much earlier than the cortex, which is most extensively developed in humans and believed to carry out the higher "cortical" functions (things like language processing and abstract reasoning) that define much of what it is to be human [19].

Thanks to research like this, which had identified the likely components and circuits of emotion, a quite different approach to studying the neural basis of emotion became possible in the 1940s when Robert Heath (1915–1999), a neuroscientist at Tulane University, used electrodes to stimulate specific regions of people's brains and noted the emotional reactions that followed. Known as evoked potential studies [20], Heath's researches suggested that the so-called limbic system (the structures described above) were only part of a much more extensive collection of emotional "circuitry" that seemed to extend throughout the brain. Famously, Heath also discovered certain regions of the brain around the septum (in both animals and human patients) that came to be known as "pleasure centers": places where electrical stimulation produced immediately pleasurable and deeply satisfying feelings.

Heath's research took a new twist in 1954 with a now-classic experiment by James Olds and Peter Milner. They implanted an electrode in the septum of a rat and wired it up to a switch that the rat could press all by itself. To their surprise, not only did the rat "self-stimulate", pressing the switch to deliver a tiny burst of pleasurable electric current, but it did so thousands of times an hour. Olds and Milner ran a similar experiment with human patients and showed, quite remarkably, that people were just as fond of intra-cranial self-stimulation (ICSS) as their whiskered counterparts. This groundbreaking research offered important and immediate benefits. Heath, for example, reduced pain in cancer patients and seizures in epileptics using electrical stimulation of this kind. Others carried the idea much further than it was ready to be taken, claiming that the "pleasure-center" theory should inform sweeping policies of social reform: British physiologist H.J. Campbell's 1973 book The Pleasure Areas was typical. Since then, the theory has fallen into disfavor with the apparent discovery that ICSS taps into brain circuits of craving and addiction, not those of reward [21].

Ever since the James-Lange theory, a central question about the neural basis of emotion has been how our fast, instinctive emotional reactions work with more measured, cognitive responses that typically follow later. In 1962, a pair of social psychologists at Columbia University, Stanley Schacter and Jerome Singer, added support to some of the ideas James and Lange had originally proposed. Schacter and Singer injected their subjects with adrenaline, to increase their arousal, and put them in a room with stooges who were told to behave in a particular way—to behave angrily or euphorically, for example. Perhaps not surprisingly, the subjects who were not told about the purpose of their injection behaved in the same way as the people around them; subjects who were informed about the purpose of the injection were unaffected by their surroundings. Although the results of this now-classic experiment have been open to widely differing interpretations, they do add support to the idea of emotion as a nonspecific state of arousal whose meaning we derive from context.

Psychologists and physiologists continue to probe the detailed circuitry of the emotional brain today. "Circuitry" is an appropriate word, and much more than a metaphor, because decades of research now seem to have established that emotions occur in the brain when neurotransmitter chemicals flow around fairly well-defined pathways. The New York neuroscientist Joseph LeDoux, for example, has devoted his career to exploring the neural circuitry that underlies our emotion of fear: a threat, like a snake in the woods, is perceived by the visual thalamus (that part of the thalamus devoted to processing sensory input from the eyes), which triggers a "quick and dirty" fear reaction in the amygdala and a much slower, more measured response in the visual cortex that also, in time, refines the reaction in the amygdala ("Hang on, that's a stick not a snake"). On this reading, fear is a fast-track, instinctive survival mechanism that makes all the difference between life and death. LeDoux makes it clear that we don't simply have one "emotional brain":

"Emotions are indeed functions involved in survival. But since different emotions are involved with different survival functions—defending against danger, finding food and mates, caring for offspring, and so on—each may well involve different brain systems that evolved for different reasons. As a result, there may not be one emotional system in the brain but many."[22]

Although there is no reason why parts of the brain (or circuits) that control anger or fear should have anything to do with other emotions, such as sadness, the sheer complexity of human emotions like love or jealousy may reflect the way different emotional circuits interlink or tap into common components. Other researchers have begun to explore these other emotions, happiness among them.

Inside the happy brain

Just as cognitive neuropsychology has allowed neuroscientists to map regions of the brain devoted to obviously cognitive functions such as short-term memory and language processing, so a similar approach is successfully charting out the territory—both the components and the circuits that link them together—of our emotions. That territory encompasses parts of the subcortical "old brain" (in evolutionary terms), such as the amygdala and hippocampus, which are largely responsible for our immediate, instinctive reactions to people, events, and other things relevant to our survival. The territory also takes in the "newer" brain, the cortical areas "built on top" of those subcortical foundations, which have evolved more recently, and that distinguish humans from animals. How the cortical and subcortical areas work together is still not known. There are connections running in both directions between the "emotional", subcortical brain and the "rational" cortex above. More connections run up from the subcortex to the cortex than in the opposite direction, which is probably why we so much at the mercy of our emotions and why top-down, rational thought struggles to control such things as phobias, stress, and affective disorders like depression.

Richard J. Davidson, director of the Laboratory for Affective Neuroscience at the University of Wisconsin-Madison, is one of the world's leading neuroscientists specializing in how the brain handles emotions. The name of his laboratory is something of a giveaway: "affective neuroscience" is the term Davidson has coined for research into how and why the brain gives rise to "affect" or the mood states that we would call happiness (well-being) or sadness (depression). Crucially, it's an interdisciplinary science that brings together physiologists, psychologists, cognitive scientists, and the social psychologists who have traditionally researched emotion, often from an anthropological perspective. It was Davidson who, ingeniously, wired up a meditating monk to a brain scanner and demonstrated readings that were, in the words of Wired magazine, "off the chart for happiness" (see box). Davidson sees his mission as the emotional equivalent of cognitive neuropsychology: first, to break emotion down into its components; second, to see how different parts of the brain "instantiate" (include or give rise to) those emotional components.

One of the key findings Davidson has to explain is the self-evident but nevertheless crucially important observation that individuals react in different ways to different emotional stimuli: some of us are easily upset; others have a remarkable degree of resilience that can see us through all manner of troubling events. Davidson argues that this is evidence for what psychologists call a "diathesis" (effectively, a double-edged sword of an explanation)—the idea that our brain biology (genetically inherited or otherwise) gives us a predisposition to certain types of mood (or "affective style") and environmental stresses interact with this to make each of us react with the unique emotions that we do. There are many ways of categorizing affective style. Some of us react swiftly and recover quickly when challenging events try to trip us up. Some of us are more inclined to "approach" challenging stimuli and tackle them head on with a happier, more positive, and welcoming affective style that can help us achieve our goals; others are more likely to "withdraw"—with a more negative affective style that reflects such emotions as fear and disgust. Withdrawal is the safer option, but it carries the risk of missed opportunities, helplessness, and depression.

Approach and withdrawal, the yin and yang that distinguish one person's affective style from another's, play a fundamental role in happiness and well-being and seem to be controlled ("instantiated", to use Davidson's word) in quite different parts of the brain. It's appropriate now to take a closer look at the structure of the brain and see if we can answer some of our earlier questions: Where are aspects of happiness or well-being actually taking place and, perhaps more to the point, how? What makes one person's emotional brain different from another's—and, other things being equal, is this what makes one person happier than another?

The Amygdala

Using brain scans and a variety of other neuroscientific tools, researchers like Richard Davidson have identified key areas of the brain that seem to be implicated in controlling happiness. Not surprisingly, the limbic system—the brain's emotional heartland—is among them. The amygdala (we have one amygdala at the base of each hemisphere of our brains) plays a central role in processing information about outside events that have major emotional significance, especially those involving threats or dangers. In other words, the amygdala seems to be a kind of early-warning system that alerts the cortex to looming threats, triggering at the same time fear or withdrawal reactions that can be toned down if and when the cortex has had time to decide there is really nothing to be afraid of. (Joseph LeDoux's book The Emotional Brain is a detailed exploration of this idea, though his later article Rethinking the Emotional Brain radically reinterprets some of his earlier work.) One recent study found that patients who have bilateral amygdala damage (in other words, both amygdalas are impaired) rate strangers as more approachable and trustworthy than ordinary people would consider them [23], for example. A variety of other studies have noted that patients with depression seem to have enlarged amygdalas or amygdalas with greater activation. One post-mortem study of patients who committed suicide found they had significantly greater numbers of serotonin receptors in their amygdalas. But quite different studies have consistently reported that the amygdala is involved in laying down long-term memories, which begs a question: how are these findings related? Some researchers, including Richard Davidson, speculate that "dysfunctional interactions" between the amygdala and parts of the cortex may lead to a tendency to dwell on negative memories and not see that the reality of the outside world doesn't necessarily reflect the darkness of the world within. There is also some evidence that the amygdalas in our two hemispheres work in oppositional ways: one recent study of gambling found the left amygdala showed greater activation when subjects were winning money, while the right amygdala was activated more when they lost money [24].

The frontal cortex

Interestingly, the phrenologists located "agreeableness" and "mirthfulness" towards the front of the brain—and that's exactly where neuroscientists believe such qualities can be found today [25]. The prefrontal cortex (PFC; as its name suggests, the front part of the cortex) also plays a major role in emotional processing; different sub-regions within the PFC appear to be specialized for different tasks, although exactly what each region does is still not known [26]. Key components include the orbital prefrontal cortex (OFC) and ventromedial prefrontal cortex (VFC), next to one another on the underside of the frontal cortex, and the dorsolateral prefontal cortex (DFC), higher up and on the outside. According to psychologists Earl Miller and Jonathan Cohen, the prefrontal cortex manages goals and the way we achieve them [27]; in other words, the PFC may act as a kind of working memory for affect. Davidson and his colleagues speculate that the PFC does this by balancing approach and withdrawal: enquiring, left-sided regions of the PFC seem to be involved in making us approach things to satisfy our goals—and seem to be implicated in positive affect; vigilant, right-sided regions make us withdraw—and are more implicated in negative affect. There is some speculation that the OFC and VFC are involved in the management of rewards and punishments, the left-sided OFC responding to rewards and the right-sided OFC to punishments.

The apparent specialization of different parts of the PFC is also borne out by neurological studies of patients with mental illness. Damage to the anterior (front part of the) prefrontal cortex of the left hemisphere is typically linked to depression; damage to similar areas of the right hemisphere can prompt expansive, manic reactions. In other words, the implication is that the left-hemisphere prefrontal cortex plays a key role in positive affect (happy moods), while the right-hemisphere prefrontal cortex seems to do the reverse. Davidson and his colleagues demonstrated this elegantly by showing happy or sad film clips to people known to have greater levels of either left-sided or right-sided brain activity in the prefrontal cortex. Those with more activity on the left side reacted more positively to the positive clips than those with more activity on the right side; similarly, people with higher levels of right-side activity to begin with reacted more negatively to the negative film clips [28]. In other experiments, when normal subjects have been asked to make themselves feel sad, neuroscientists have noted a marked increase in blood flow (suggesting higher levels of activity) in various parts of the frontal cortex. Richard Davidson sums up research into the role of the frontal cortex thus: "We suggest that taking an active role in life and appropriately engaging sources of appetitive motivation, behaviors that are characteristic of left frontal individuals, may contribute to higher levels of well-being." [29]

The hippocampus and the anterior cingulate cortex (ACC)

Best known for its role in helping to store long-term memories, the hippocampus—the seahorse-shaped structure adjoining the amygdala—also seems to play a key role in our emotional reactions. Davidson and his colleagues have suggested the hippocampus is a kind of emotional "chaperone" that helps to ensure our behavior is appropriate to its social context. This may explain why people with hippocampal damage often show emotions that are quite inappropriate at a particular time and place. Patients who suffer from post-traumatic stress disorder (PTSD), such as victims of war and violent attacks, can experience sudden extreme emotional reactions to quite innocuous stimuli: war veterans who burst into tears or dive behind the sofa when cars backfire are just one example. The anterior cingulate cortex (ACC) also seems to be involved in emotional processing, monitoring conflicts and triggering other brain circuits to carry out more detailed processing when they occur.

Putting it all together

It's still too early to say exactly how these different components of the emotional brain work together to produce happiness, unhappiness, and other emotions: there are many connections running both ways between cortical areas (like the PFC) and subcortical areas, including the amygdala. It seems likely that the cortical and subcortical areas work in opposition, with the amygdala, for example, shooting first (triggering fast emotional reactions) and the cortex asking questions later (processing those emotional reactions further or trying to inhibit them some time afterward if they appear to be inappropriate).

Richard Davidson believes "affective style"—how different people react to different emotionally laden stimuli—is also of prime importance in understanding why people are so different when it comes to emotions. Some people react quickly or slowly to emotional challenges; others react to a greater or lesser degree; some recover more quickly. Davidson's research suggests the way people respond is caused by the relative contributions their left and right prefrontal cortices are making to the reaction. People with greater activity in the left, frontal cortex tend to be happier and more optimistic (show greater positive affect) than people whose right frontal cortex is more active. Similarly, people with greater activity in their amygdala (and the right-hemisphere amygdala in particular) are much more likely to be at risk from depression. This suggests some people are more at risk from environmental factors than others, especially because they seem to take more time to recover from negative stresses. Similar findings have also been confirmed in rhesus monkeys. According to Davidson, happier people can maintain a positive level of well-being because they can regulate negative emotions more effectively and reduce the time for which they last.

Just how the cortical and subcortical areas work together remains one of the key mysteries of the emotional brain. But the division certainly fits our experience of sometimes being "in two minds" about things, having the sense of our "head" (our rational cortex) telling us one thing and our "heart" (actually, our instinctive subcortex) telling us something else. It supports complex models of mental illnesses such as depression, which clearly have cognitive, behavioral, biological, and neurological components, and it explains why cognitive treatments can sometimes tackle these illnesses (by tapping into the emotional circuitry at the cortical level) as successfully as drugs (which alter our negative cognitions perhaps by influencing the same circuits at a more fundamental, biological level).

Looking to the future

In the end, perhaps there is nothing more depressing than the idea that our moods are hard-wired in our brains—an essentially deterministic view of psychology that has our happiness or sadness contingent upon sudden power spikes in the emotional circuits. Such a view could be immensely liberating for some: people whose lives are crippled by severe mental illness are often relieved to find that what bothers them really is "all in the mind"—ultimately "all in the body"—and therefore susceptible, in time, to a medical cure. Richard Davidson and his colleagues have also considered how violence and impulsive aggression might be caused by disorders of emotional regulation, themselves caused by faults in the emotional circuits involving the PFC, amygdala, and other brain structures that regulate emotions. Imagine the extraordinary social repercussions of tracing violence to neural abnormalities and coming up with medical or behavioral treatments that put people in better control of their emotions and lives [30].

Yet despite the obvious benefits of understanding the neural basis of human behavior in cases like these, most of us are unlikely to find the idea of biologically determined moods so appealing. Quintessentially romantic, moods color our lives; articulate psychiatric patients have often noted with some regret the passing of their demons when they are eventually "cured". Kay Redfield Jamison, a psychiatrist who has charted her own, lifelong battle with manic depression, makes a telling point when she talks of the "bittersweet exchange" of her intense, psychotic moods for a settled life on permanent medication:

"How can one ever bring back the long summer days of passion, the remembrance of lilacs, ecstasy and gin fizzes that spilled over a garden wall, and the peals of riotous laughter that lasted until the sun came down or the police arrived?" [31]

Perhaps it's just as well that current neuroscientific wisdom does not support such a fatalistic view—or, at least, does not support it entirely. Richard Davidson champions the idea of a diathesis in which people's biological (or perhaps even genetic) predisposition makes them respond differently to different kinds of environmental challenge. Some people, in other words, are indeed dealt a better hand for happiness than others by having brains that are better wired for happiness to begin with. But that does not mean the rest are condemned to a lifetime of poor adaptivity and depression.

Various different kinds of treatments for mental illness—from behavioral and cognitive treatments to drugs and electroconvulsive "shock" therapy—are effective to a greater or lesser degree in tackling illnesses such as depression. This suggests the mental circuitry of emotion is not immutable: it is "plastic" and its behavior can be changed by intervention. Although little research has been done into how, for example, cognitive therapy actually reduces the symptoms of depression, some studies have confirmed that it produces changes in brain activity comparable to those produced by medication. Using brain scans, Richard Davidson has also demonstrated that training in meditation techniques can have a dramatic effect not just on left-sided activity in the frontal cortex (strongly correlated with positive affect), but also on immunity to physical ailments (remarkably, for example, it seems to increase influenza antibodies). The Dalai Lama, author of a book on The Art of Happiness, notes that neuroscience too has a crucial part to play in our understanding of well-being:

"The systematic training of the mind—the cultivation of happiness, the genuine inner transformation by deliberately selecting and focusing on positive mental states and challenging negative mental states—is possible because of the very structure and function of the brain... But the wiring in our brains is not static, not irrevocably fixed. Our brains are also adaptable." [32]

It's a suitably optimistic thought. Much like computers, our brains do what they do through a combination of hardware (neuroanatomical structures) and software (cognitions and chemicals). Even if the hardware constrains how we think and who we are, we can always change the software, reprogramming our minds—at least in theory—to make our lives happier and more fulfilled.

Find out more

On this website

• The science of chocolate
• Introduction to psychology
• 10 great psychology experiments

Books

Neuroscience

• The Human Brain Book by Rita Carter (London: DK, 2009/2019) is a brain-imaging atlas—a comprehensive guide to our brains and what happens inside them.
• Mapping the Mind by Rita Carter (London: Phoenix/Orion, 2013) is a 21st-century spin on phrenology, a clear, colorful, guide to neuropsychology that explains how scientists have successfully pinpointed mental functions and circuits in the brain.
• The Emotional Brain by Joseph LeDoux (New York: Simon & Schuster, 1998) is a good introduction to the neuroscience of emotions. Although it concentrates mainly on fear, much of LeDoux's commentary is relevant to other emotions as well.
• The Man Who Mistook his Wife for a Hat by Oliver Sacks (New York: Simon & Schuster, 1998/London: Picador, 1986) is an entertaining collection of case-studies of patients whose bizarre behavior makes telling points about how the brain operates. The title takes its name from a patient suffering with prosopagnosia, a highly selective neurological disorder that disrupts a person's ability to recognize faces but leaves other mental functions intact.

Emotions

• How Emotions are Made by Lisa Feldman Barrett. (New York: Macmillan, 2017). A very simplified introduction to Barrett's theory of constructed emotion.
• Handbook of Emotions by Lisa Feldman Barrett, Michael Lewis & Jeanette Haviland-Jones (eds). (New York: Guilford Press, 2016) is a comprehensive, library-type reference book that covers most aspects of emotional behavior in. Its many chapters are not too difficult for nonspecialists to understand.
• The Psychology & Biology of Emotion by Robert Plutchik (New York: HarperCollins, 1994) is a more academic book offering a more detailed look at how emotions arise in the components and circuits of the brain.

General

• A History of Psychiatry by Edward Shorter (New York: John Wiley, 1997) is a highly readable but sometimes controversial account of how psychiatry and the treatment of mental illness have gradually shifted onto a progressively more medical and scientific footing.
• Authentic Happiness by Martin Seligman (New York: Simon & Schuster, 2002) introduces the concept of "positive psychology", and explains why the author believes psychologists need to shift their focus from researching depression to understanding happiness and mental well-being.
• Flourish by Martin Seligman (New York: Free Press/Simon & Schuster, 2011) is an updated version of Seligman's ideas based on the ideas originally outlined in Authentic Happiness.

Articles

• How to make the world happier—and why it should be our first priority by Richard Layard. The Guardian, January 19, 2020. Can a culture of gentleness replace a culture of excessive individualism?
• Get Happy: Four Well-Being Workouts by Julie Scelfo. The New York Times, April 5, 2017. Martin Seligman shares four simple methods of feeling better about your life.
• A Formula for Happiness by Arthur C. Brooks. The New York Times, December 14, 2013. It's all very well talking about the "science of happiness," but only if we know what "happiness" actually means. According to this author, "we do best to pour ourselves into faith, family, community and meaningful work."
• Happiness, Philosophy and Science by Gary Gutting. The New York Times, August 31, 2011. It's all very well talking about the "science of happiness," but only if we know what "happiness" actually means.
• A New Gauge to See What's Beyond Happiness by John Tierney. The New York Times, May 16, 2011. Why "positive psychology" pioneer Martin Seligman has come to view happiness as a limited concept.
• This is the greatest good by Richard Layard, The Guardian, September 13, 2009. Happiness is the key measure of society's achievements, argues the LSE economist.
• The Science of Love by Matthew Herper, Forbes, June 28, 2004. How and where does the brain produce the emotion we call love?

Websites

• The Center for Investigating Healthy Minds (CIHM): Richard Davidson's website contains information about his research and some of his recent scientific papers
• Joseph LeDoux's website: Information about LeDoux's pioneering research into fear and the brain
• The Mind and Life Institute: A working collaboration between neuroscientists and Bhuddists.
• The History of Phrenology on the Web: A fascinating archive of phrenological material by Dr John van Wyhe.

References

[1] Philosophers call this the "principle of sufficient reason": nothing happens without a cause.

[2] The Age of Spiritual Machines: When Computers Exceed Human Intelligence by Raymond Kurzweil. New York: Viking/Penguin, 1999.

[3] The brain doesn't actually light up, of course. fMRI scans reveal which bits of the brain are most active and the computerized pictures they draw show these areas more brightly and colorfully: our brains light up only in other people's minds.

[4] From R.H. Wilkins Neurosurgical Classics (New York: Johnson Reprint Corporation, 1965). Quoted in K. Walsh. Neuropsychology: A Clinical Approach. Edinburgh: Churchill Livingstone, 1987.

[5] "...original and independent mind..." See Ch11 "Wernicke" by Mario Horst Lanczik, Helmut Beckmann and Gundolf Keil in German Berrios and Roy Porter (eds). A History of Clinical Psychiatry. London/New York: Athlone Press, 1995.

[6] Quoted in A History of Psychiatry by Edward Shorter (New York: John Wiley, 1997), p81.

[7] Quoted in "Freud" by Martin Evan Jay in Encyclopedia Britannica, 15th edition, 1999.

[8] Chapter 5. "The Psychoanalytic Hiatus" in A History of Psychiatry by Edward Shorter (New York: John Wiley, 1997), p145.

[9] Cognition and Reality by Ulric Neisser. San Francisco: Freeman, 1976.

[10] Chapter 2: "Souls on Ice" in The Emotional Brain by Joseph LeDoux. Paperback edition p.25.

[11] The Emotional Brain. Paperback edition p.39.

[12] King Lear, Act III Scene 6. Spoken by Edgar. The New Penguin Shakespeare. Edited by G. K Hunter. London: Penguin, 1972.

[13] "The Myth of Mental Illness". Thomas S. Szasz. The American Psychologist, 15:113-118 (Feb.), 1960. (p21 my copy)

[14] See R.D.Laing: A Divided Self by John Clay. London: Hodder & Stoughton, 1996.

[15] From A Divided Self by R.D. Laing. London: Tavistock, 1960. Penguin edition pp163-4.

[16] For a review of changing attitudes to schizophrenia, see "Schizophrenia" by Trevor Turner in A History of Clinical Psychiatry by German Berrios and Roy Porter (eds). London/New York: Athlone Press, 1995.

[17] See A History of Psychiatry by Edward Shorter. New York: John Wiley, 1997.

[18] According to Richard Davidson: "... the physiological response to a stimulus is antecedent to the emotional experience (the felt emotion); more properly, the physiological response (sensation followed by motor output) in fact provides the basis for the emotional experience." From "Emotion, Plasticity, Context and Regulation: Perspectives From Affective Neuroscience." Davidson, Jackson, and Kalin, Psychological Review, 2000, Vol 26, No 7, 860-900.

[19] Now we can begin to see why pop-psychology ideas like "left-brain"/"right-brain" are potentially so misleading, for the divisions between any two parts of the brain—the front and the back, the top and the bottom, the cortex and the structures that lie beneath it—may be just as revealing. Consider, for example, the distinction between the limbic system, often described as the evolutionarily old "visceral" or feeling brain and the cortex that covers it. Here is as clear a distinction between "emotional" and "rational" brains as pop-psychologists like to make between the so-called "left brain" and "right brain".

[20] Because, in the science of electricity, potential is another word for voltage.

[21] See Martin Seligman's Authentic Happiness p. 105.

[22] From The Emotional Brain by Joseph LeDoux, Ch 4. "The Holy Grail". Paperback edition p.103. LeDoux makes a similar point elsewhere: "There is no such thing as an 'emotion' facility in the brain and no single system dedicated to this phantom function. If we want to understand the various phenomena we call emotion, we have to focus on specific types." Emotion—iceberg of the brain" by Joseph LeDoux. In Mapping the Mind by Rita Carter, p.155.

[23] Adolphs, Tranel, and Damasio (1998) quoted in Davidson "Toward a Biology of Personality and Emotion".

[24] Zalla et al, 2000. Quoted in Davidson "Well Being and Affective Style".

[25] Walsh diagram p15.

[26] Davidson "Toward a Biology of Personality and Emotion".

[27] Miller & Cohen (2001). Quoted in Davidson "Affective Neuroscience and Psychophysiology".

[28] Wheeler, Davidson, and Tomarken (1993). Quoted in Davidson "Affective Neuroscience and Psychophysiology".

[29] Urry et al. "Making a Life Worth Living." (2004). Psychological Science Vol 15 Number 6 p367.

[30] Davidson et al. Science 28 July 2000, p.591.

[31] Kay Redfield Jamison. "An Unquiet Mind" New York: Alred A. Knopf, 1995. (p211 my copy).

[32] Dalai Lama and Cutler. "The Art of Happiness" (1998). pp44-45. Quoted in Davidson "Well Being and Affective Style".

[33] Blood and Zatorre. "Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion". PNAS, September 25, 2001, Vol. 98 No. 20 pp11818-11823.

[34] Dana M. Small, Robert J. Zatorre, Alain Dagher, Alan C. Evans and Marilyn Jones-Gotman. "Changes in brain activity related to eating chocolate." Brain, Vol. 124, No. 9, pp.1720-1733, September 2001.

[35] Paper delived to 32nd Annual Meeting of Society for Neuroscience.

[36] MS George, TA Ketter, PI Parekh, B Horwitz, P Herscovitch and RM Post. "Brain activity during transient sadness and happiness in healthy women." Am J Psychiatry 1995; 152:341-351.

[37] RD Lane, EM Reiman, GL Ahern, GE Schwartz and RJ Davidson. "Neuroanatomical correlates of happiness, sadness, and disgust." Am J Psychiatry 1997; 154:926-933.

[38] John van Wyhe, The History of Phrenology on the Web, (http://www.historyofphrenology.org.uk/).

[39] Celeste Biever, "Rat Brain Flies Jet," New Scientist, 25 October 2004.