Personal Health

It's a Jungle in There: Our Brains Not As Evolved As We Might Think

The human brain will probably continue to grow in size and capacities, barring the potential catastrophes that this amazing organ can create for the world and itself.

Anatomically, modern humans evolved from our chimplike ancestors around 100,000 years ago, although it took another 50,000 years for our brains and culture to evolve sufficiently to make us capable of language, planning, and creativity. But this extended, complex history has a downside: the more recently emergent aspects of our brains—which give us astonishing powers of thought, logic, imagination, empathy, and morality—must share skull space with the ancient brain equipment that we've inherited from our mammalian and reptilian forebears over the past several million years. So even today, one of the most basic human challenges is integrating and coordinating the complex and highly specialized systems that comprise our brains.

The neocortex, for example—the part of the brain that organizes our powers of conscious thought, imagination, and empathy—must coexist and cooperate with primitive survival networks conserved by natural selection through hundreds of thousands of generations. This means that beneath our newer equipment, capable of composing sonnets and developing computers, are structures driven by primitive instincts, unconscious impulses, and primordial fears. Within our skulls, the reptilian, ancient mammalian, and modern human brains attempt to coexist and cooperate, at least enough to get us through the day.

The American physician and neuroscientist Paul MacLean first discussed this structure, which he called the "triune brain." The basis of his theory is that the contemporary human brain resembles a site inhabited by successive civilizations, and embodies a living record of our deep evolutionary history. At its core is the reptilian brain, responsible for arousal, homeostasis, and reproduction. The paleomammalian ("old-mammal") brain, involved with learning, memory, and emotion, surrounds it. The neomammalian ("new-mammal") brain, required for conscious thought and self-awareness, sits atop the other two. These levels roughly conform to the common distinction of brainstem, limbic system, and cortex. Though MacLean's theory has many significant limitations, it can both assist us to better understand some of the most distinctive features of human experience and give us fresh insight into how psychotherapy influences brain function.

MacLean suggested that our three brains don't necessarily work well together because each of them processes information in a distinctive manner and has a unique agenda. The functions of the reptilian brain, which drive our instincts and behaviors—fear, rage, eating, mating—retain a good deal of executive control over our actions, while only a small region of the cortex is capable of conscious awareness and articulating its strategies. This means that multiple levels of the brain often vie for dominance simultaneously and in conflict with each other, without our conscious awareness—an idea that parallels Sigmund Freud's conception of the relationship between the conscious and unconscious minds.That so much neural processing occurs outside of conscious awareness and that executive decisions at multiple levels can oppose one another lay the groundwork for considerable inner conflict. To these evolutionary layers are added the complexities of two cerebral hemispheres, a variety of vertical networks integrating the layers of the brain, and the variations of brain organization resulting from gender, vagaries in development, and influences of the cultural environment. In an image suggested by the British cultural philosopher and management consultant Charles Hampden-Turner, the human brain is an anachronistic menagerie, which confronts the psychotherapist with the challenge of treating a human, a horse, and a crocodile attempting to inhabit the same body.

The Social Brain

The potential for miscommunication among the networks of our brains might not be so bad if we lived in isolation, but our brains are social organs, which require sustained connection with other brains. At birth, we're totally dependent on our caretakers for our survival. If an average reptile is born knowing how to perform the basic tasks of survival—getting food, fighting, and mating—we're born dumb, so to speak. Our saving grace is that as babies we know how to attach to our parents and stimulate them to attach to us.

For human babies, survival doesn't depend on how fast they can run, climb a tree, or tell the difference between edible and poisonous mushrooms: it depends on their abilities to detect the needs and intentions of those around them. Throughout the millennia that we Homo sapiens have inhabited the earth, if we've been successful in our early relationships, we have food, shelter, protection, and a decent shot at eventually producing children of our own.

Our prolonged dependency allows for an increasing amount of brain development to occur after birth, making each human brain an experiment of nature—a unique blending of genetics and experience. Our parents are the primary environment to which our baby brains adapt, and their unconscious minds are our first reality. Their nonverbal communications and patterns of responding to our needs when we're babies shape not only our perceptions of ourselves and the world, but also the architecture of our brains. Because the first few years of life are a period of exuberant brain development, early experiences have a disproportionate impact on the shaping of our neural systems, with lifelong consequences.

Our brains are inescapably social, their structure and function deeply embedded in a group of other brains—the family, the tribe, the society. Because we've evolved in this context, we've individually developed the ability to link with other brains, attuning with each other, regulating each other's emotional systems, helping to grow each other's neural networks. Similarly, the ability to link with, attune to, and help build new neural connections in the brains of clients is at the heart of psychotherapy. This is why therapists are in a position to counterbalance some of natural selection's less stellar choices.

The Primacy of Early Learning

While being embedded in groups has been necessary for our survival and development as human beings, it can create friction and dysfunction. What makes the combination of a complex brain and human interdependency such a problem? From birth, the primitive regions of our brains are deeply affected by our social and emotional experiences, while our more sophisticated brains still haven't "come online." As a result, a great deal of important learning takes place while our primitive brains are in control. For most of us, these learned reactions and feelings remain forever inaccessible to conscious memory or modification. We mature into self-awareness years later, having been programmed by early experience with assumptions that we accept as truth.

The powerful influence that early experience exerts over our brains can be both good and bad news. The good news is that the individual brain is well-suited to survive in whatever social environment into which it's born. Parents, family, and culture shape each of our brains for maximum adaptation to our social niche. In good times, and with good-enough parents, this early brain-building will serve us well in adulthood. The bad news comes when the surrounding factors aren't so favorable, as when parental psychopathology shapes the baby's brain in ways that, though they optimize childhood survival, prove to be maladaptive later in life. The child's brain is shaped with its most primitive survival mechanisms—loosely speaking, its unconscious "horse" and "crocodile" mechanisms—operating at full tilt to react to abuse, for example, with dissociation and other defenses, and insufficiently modulated by the regulating, late-developing cortex.

We see this in abused and neglected children, who often enter adolescence and adulthood without a clear picture of their early experiences, but with a variety of symptoms, such as explosive anger, eating disorders, or drug and alcohol problems. They have identity disturbances and a poor self-image, exacerbated by angry feelings and negative behaviors. Like the brains of veterans with PTSD, the brains of these children have been shaped to survive combat, but are ill-equipped to negotiate the peace.

The Speed of Unconscious Processing

To survive, animals have to be tough or fast. The tortoise and the hare are good examples of these different, equally viable, survival strategies. Our cortex distinguishes our brains from those of both hares and tortoises, but further inside, all three brains are pretty similar. Our cortex allows us far greater response flexibility than our more primitive cousins have: we can think things through, rather than respond instinctively. But thinking through options takes time, and a speedy, unthinking reflex is sometimes more adaptive, more likely to save us from danger, than the ability to consider all the options. In the interest of survival, we've retained many primitive responses and automatic subcortical processes.

For example, it takes approximately 500 to 600 milliseconds for our cerebral cortex to process an experience and register it in conscious awareness. By contrast, the amygdala, the core of our fear and attachment circuitry, located in the old-mammalian brain, can react to a potential threat in less than 100 milliseconds. This means that by the time we've become consciously aware of an experience, it's already been processed and reprocessed in the brain's more primitive regions, activating memories and triggering neural patterns generated by past learning. When we finally realize there's a need to take action of some kind, we think we're making a conscious choice, but most likely, the choice has already been made for us by our more primitive brain centers. The brain somehow creates the illusion that we're living in the present moment and are acting with free will based on conscious deliberation, but extensive evidence shows that this isn't the case. So, when we think we're directly experiencing what's going on around us, our conscious awareness is primarily the result of what's already occurred within our brains—fully 90 percent of the input to the cerebral cortex comes from internal neural processing.

The predominance of unconscious processing makes sense for situations that require rapid appraisal and reflexive action based on past learning; behaving as if we still had the brains of an ancient gazelle or lizard keeps us alive in situations requiring immediate fight or flight to avoid imminent physical danger. But for humans living in the 21st century, this arrangement isn't always socially or personally convenient, to say the least. Because this unconscious processing is both automatic and beyond our awareness, it can create distortions and ruts in our thinking—limitations that keep us frightened, withdrawn, and confused without our knowing why. Think of the veteran who ducks when he hears a car backfire, even years after combat, or runs for cover when a news helicopter flies overhead. This behavior worked well for the fearful beast scanning the ancient savannah, but it produces misery for the human trying to adapt to ordinary life in a modern, urban environment.

Attachment schemas—implicit emotional memories derived from the summation of our early experiences with caretakers, laid down in the "old" brain regions that formed before the cortex came fully online—are another example of the unconscious processing structure of our brains. These schemas become automatic predictions of outcomes that shape our conscious experience of others by activating lightning-fast systems of emotional evaluation, which lead us to seek or avoid proximity. A woman who experienced early abandonment may be perfectly capable of starting new relationships as an adult. At a certain point, however, intimacy may trigger an attachment schema that leads her to become frightened and flee from a potentially healthy relationship. The impulse to run, driven by primitive brain circuitry, is overpowering and inescapable. The true reasons for her decision to break things off, stored in her brain within implicit networks dedicated to fear regulation, remain for her aspects of what British psychoanalyst Christopher Bollas accurately described as the "unthought known." 

The illusions constructed by our brains of living in the present moment and being in control of our behaviors have their own survival advantages, however, the foremost being the ability to be assertive and doubt-free in the face of a complex and confusing world. At the same time, this adaptive capacity to tamp down our own, probably realistic, self-doubts has a serious drawback: we can become so confident in our personal perspectives and beliefs that we're unable to consider alternatives to them. The woman described above, for example, may come up with a list of irrelevant, yet personally persuasive, reasons for fleeing the relationship, because she has no access to the true source of her fear—hidden, so to speak, in the more primitive regions—and isn't able to open up to her partner's thoughts and feelings about their life together.

It's an odd paradox of therapy that we can help our clients become more consciously clear-sighted about themselves by helping them become aware of the unconscious, irrational impulses arising from the older regions of the brain. That's why openness to questioning one's assumptions—particularly when they're incorrect and self-defeating—is a key aspect of psychological mindedness and a predictor of a positive outcome in psychotherapy. We encourage clients to talk about their impulses with the hope that doing so will integrate the calmer, more reasonable, inhibitory cortical input of their brains with the regions organizing primitive urges. Psychotherapy takes a skeptical perspective when it comes to the "reasoned" output of our brains, understanding that our conscious thoughts, emotions, and self-image are based largely on reactions and feelings totally outside of our awareness and often out of sync with our actual circumstances.

The Bias toward Anxiety and Fear

As we've seen, human survival, like that of all animals, is based on rapid and accurate decisions to approach what's safe and avoid what's dangerous. Therefore, we maintain some common anxieties—fear of spiders, snakes, open spaces, and heights—which appear to be hard-wired and linked to the survival requirements of our tree-dwelling ancestors. Because vigilance and rapid approach-avoidance reactions are central mechanisms of survival, cognitive therapist Aaron Beck postulated that evolution favors an anxious gene: natural selection probably weeded out our past relations who were too "laid back."

The core of the neural circuitry involved in fear and anxiety is the amygdala, a structure we share with our ancestors who only had to navigate their physical environments and basic social interactions. Unfortunately, these primitive fear circuits deep inside our brains still have a lot of power and are unable to tell the difference between real and imagined danger. We now have the capacity to experience anxiety associated with just about anything—from public speaking, to existential despair, to the thought of an asteroid striking the earth.The amygdala is central not just to the immediacy of fear, but to the memory of fear. The reason we easily forget someone's name but have difficulty forgetting a traumatic experience is that the hippocampus and the amygdala have different neuroplastic properties. The amygdala, which controls our unconscious memory, retains a constant dendritic profile, which means that the wiring established by stressful situations persists unchanged. The role of the amygdala is to remember threats and apply the "lessons" contained in these memories to future circumstances, while generalizing fearful experiences to as many situations as possible. That's why a panic attack outside the home can lead to agoraphobia, or getting scratched by a cat can result in a fear of all furry animals.

In contrast, the hippocampus is like an Etch A Sketch, ready to be turned over repeatedly, shaken, and influenced by experience after experience. It's constantly remodeled in response to new details, and will easily learn to differentiate memories of one furry animal from another.

The fear and anxiety resident in older parts of our brains can make us cognitively and emotionally rigid. We become afraid of taking risks and learning new things, resulting in what psychoanalyst Wilhelm Reich described as a tendency for those who become sick to remain sick. Once our brains have been shaped by fear to perceive, think, and act in specific ways, we tend to remain in cognitive and emotional ruts that are reinforced by what we perceive as our continuing survival needs. In other words, an agoraphobic person functions as if the following were true: "I haven't set foot outside my house in 10 years because of my agoraphobia. I'm still alive, which must be because I haven't set foot outside my house in 10 years." The mind's internal logic is self-perpetuating, making it difficult for us to find answers that differ from the ones we already know. Our chance of changing in positive ways rests on getting input from others, because our brains are shaped by others from birth and continue to be so, but our fear causes us to mistrust people and their differing perceptions.

Caring relationships aren't easily entered into, nor is it easy for us to benefit from them. Openness and trust are fragile states, even with the people we love most. The therapist's training and the therapeutic context are designed to enhance support and trust, and to provide consistent emotional availability. Within the consulting room, therapists attempt to be amygdala whisperers: we work to activate networks of new learning in the hippocampus and prefrontal cortex. Warmth, empathic caring, and positive regard create a state of mind that enhances neuroplastic processes and increases the likelihood of positive change.

The Suppression of Language under Stress

Animals surprised by a loud noise or a sound suggesting danger freeze in their tracks, become silent, and scan the environment for the threat. We share both the startle and freeze responses with our more primitive cousins. The logic of these responses is clear: being still and silent make us less likely to be seen or heard, and prepares us to respond to a potential threat. Research suggests that during these states of high arousal, the area of our brain responsible for the production of speech (Broca's area) becomes inhibited. Thus, the conservation of the ancient reptilian and old-mammalian startle-and-freeze responses in the new-mammalian brain may result in diminished capacity for language in certain situations.

This is a high price for a human to pay for being afraid. Putting our feelings into words and constructing narratives of our experiences contribute invaluably to emotional regulation, the integration of neural networks of emotion and cognition, and the experience of a coherent sense of self. This artifact of evolution, which silences people during times of danger or attack, is especially problematic in situations of abuse, or when people have endured the "unspeakable horrors" of torture, war, or the extermination of friends and family.

An additional problem connected to this primitive, built-in instinct to freeze and go silent results from the fact that Broca's area contributes to networks of prediction and anticipation. Its inhibition during times of danger or attack thus affects people's ability to learn from the experience—which may be a reason why traumatized individuals seem to have more than their share of subsequent accidents, bad relationships, and misfortune. The compounded loss of words and predictive abilities enhances the long-term impact of the trauma by increasing the probability of dissociation and revictimization.

Wired for Projection and Self-Deception

Human brains possess neural circuits that become activated as we observe and interact with those around us. Neurons called mirror neurons in the premotor regions of our frontal lobes (first discovered in macaque monkeys) fire when we observe someone engaging in a specific behavior, such as saying a word or grasping an object. Some mirror neurons are so specific that they fire only when an object is grasped at certain angles by particular fingers; these neurons fire when we see the action performed by someone else and fire again when we perform the action ourselves. Mirror neurons link observations and actions, allowing us to (a) learn from others by watching them, (b) anticipate and predict others' actions, and (c) activate emotional states supportive of emotional resonance and empathy. All three of these functions support group cohesion and the spread of culture.

Human brains also possess neural circuits that analyze the actions and gestures of others, allowing us to develop a theory of mind—what others know, what their motivations may be, and what they might do next. The existence of these neural systems reflects the fact that millions of years of natural selection have been refining our brain's ability to read the emotions, thoughts, and intentions of others for the purposes of group coordination and defense.

We're quick to think we know others because mind reading is instantaneous and obligatory. In essence, it's a reflex of the social brain to attend to the mote in our brother's eye, and not to the beam in our own. While Freud saw these projective processes as defensive, they may be a natural byproduct of how our brains have evolved to process information. Unfortunately, evolution hasn't seen fit to invest much neural circuitry into self-awareness. Projection is automatic and lessens anxiety, while self-awareness requires effort and generates anxiety. Which do you think is going to be the norm?

Based on our neural architecture and everyday human behavior, self-awareness and personal insight don't appear to have exerted a strong pressure on natural selection. In fact, possibly it was just the reverse: self-awareness may have been selected against, because it can lead to hesitation, self-doubt, and demoralization. In fact, it's commonly suggested that depression results from seeing reality too clearly. Repression, denial, and humor grease the social wheels and lead us to put a positive spin on the behavior of those around us. Defenses help us regulate our internal state by decreasing anxiety and shame. This may be why humans have so few networks dedicated to self-insight and so many ways of distorting reality in their favor. Freud's defense mechanisms and the attribution biases of social psychology document many of these distortions.

Self-deception increases the likelihood of successfully deceiving others. If we believe our own confabulations, we're less likely to give away our real thoughts and intentions via nonverbal signs and behaviors. The best "con-men," from grifters to televangelists, can be so persuasive that their victims often refuse to believe they've been cheated, even after being shown incontrovertible evidence that they have been. Because we have these built-in information-processing biases, the most naive observer can see things about us that we may be blind to ourselves. In psychotherapy, we provide our clients not only with interpretations, clarifications, and reflections, but also with an alternative perspective (our own), which they can utilize to help discover themselves.

Why Does Neuroscience Matter for Psychotherapy?

Knowing about neuroscience is invaluable for therapists, not because it offers specific new techniques or clinical theories, but because it provides a deeper understanding of the biological power of the "talking cure." As a social organ, the brain has evolved to be affected and changed by other brains, and psychotherapy relies upon the power of relationships to trigger the neuroplastic processes necessary for learning and growth. In effect, psychotherapists are pragmatic neuroscientists, who alter the functioning and structures of clients' brains, whether or not those brains are aware of these underlying biological processes.

Information about the brain and how it evolved helps us communicate with clients about their problems in an objective and non-shaming manner. Adding a neuroscientific perspective to our clinical thinking lets us talk with clients about the shortcomings of our brains, instead of the problems with theirs. Learning about what's happening in their brains and how these billions of neural events have shaped their emotional lives and behavior is more likely to inspire interest and curiosity in clients than defensiveness and feelings of inadequacy. Identifying inherent problems in how the brain processes information and developing methods to circumvent or correct them is a solid foundation upon which to base a therapeutic alliance.

Some therapists bristle at the integration of neuroscience and psychotherapy, calling it irrelevant or reductionistic. If you have a model of therapy that works, they seem to be saying, why bother with the brain? Would Carl Rogers or Heinz Kohut have been better therapists if they'd been trained as neuroscientists? Probably not. But it's hard to grasp how the brain could be irrelevant to changing the mind.

We carry within our skulls the entire history of the brain's evolution, from its primitive origins in the fishes, up through the early and later mammals, to the unimaginably complex organ of today's Homo sapiens. And evolution hasn't stopped! The human brain will probably continue to grow in size and capacities, barring the potential catastrophes that this amazing organ can create for the world and itself, on a scale inconceivable to our ancestors even a few hundred years ago.The internal dynamics of any particular individual brain and the social dynamics of the entire human race are increasingly intertwined. Perhaps for the first time in history, we can begin to get some sense of the vast, interconnected web that joins every human brain on earth to every other. This is a cause for awe and skepticism—awe at the power and potential of our collective cerebral tapestry, skepticism about what we imagine we know. After all, we're still only animals.

Louis Cozolino is a professor of psychology at Pepperdine University and maintains a clinical and consulting practice in West Los Angeles. His latest book is "The Neuroscience of Human Relationships" (W. W. Norton).


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