Making the Connection: Strategies to Build Effective Personal Relationships (Collection) (61 page)

In thinking about people in terms of the Big Five, it therefore helps to remember that high or low rankings on each of them have tradeoffs.
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For example, people high in Extraversion enjoy the pleasures of intense engagement with others and the opportunities provided to those who take charge. Studies show that, like Bill Clinton, they tend to have many sexual partners, which, in a precontraceptive world, would have led to more children—Darwin’s gold standard for an adaptive trait. But intense engagement comes with risks; taking charge invites jealousy and insurrection; and high excitement-seeking makes it more likely to get into accidents, engage in criminal activity, get arrested, and even get killed by rivals. So, high Extraversion is a mixed blessing.

High Agreeableness is also a mixed blessing. By promoting cooperation it builds alliances that can pool resources for the common good and for protection against competing groups. But the downside of high Agreeableness is that it increases the chances of being taken advantage of. In contrast, disagreeable people are more likely to fight for themselves and
what they believe in. Studies show that people who rank high in Agreeableness tend to earn less money, even though they are valued as team players. In contrast, those who are low in Agreeableness are more likely to rise to the top of their fields.

Great achievement is also favored by high Conscientiousness, which has the benefits of purposeful self-control and long-range planning. But high Conscientiousness has the potential downsides of oppressive perfectionism and the inability to abandon well-practiced routines in the face of changing circumstances. By always taking the long view, people high in Conscientiousness may be less opportunistic, and this can translate into fewer sexual partners, fewer children, and less transmission of their genes. On the other hand, the children they have are more likely to enjoy the benefits of a devoted parent.

Only high Neuroticism might seem to have little to recommend it because it includes an increased likelihood of experiencing painful negative emotions. But the world can be a dangerous place, and emotions such as fear and sadness are adaptive if properly modulated. Studies show that high Neuroticism is correlated with high achievement and creativity in people whose other traits keep them from falling into the deep hole that can be dug by persistent emotional distress. Sigmund Freud, who was very high in Neuroticism, is an example.

In contrast with the assumption that high Neuroticism is always bad, most people who read books like this assume that high Openness is unreservedly good. This is because
they value curiosity and are interested in new ideas. But people with low Openness are happy to exchange these pleasures for the comforts of constancy and tradition.

The fact that particular rankings on a trait have advantages and disadvantages does not, of course, mean that we consciously chose the ones we have. The reason I’ve pointed out their relative costs and benefits in various social environments is to help you understand why the many gene variants that influence these traits are retained in the collective human genome. Furthermore, variants that influence one trait may have been selected to balance out others. For example, it is easy to imagine how environments that favored the selection of variants for high Extraversion might have had some of their effects balanced out by the selection of variants that favored high Conscientiousness.

Such a balance of selective forces may also control the proportion of people with high or low expression of a heritable personality trait among the members of a population.
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Consider, for example, the proportion of people with high or low Agreeableness. In a population in which almost everyone ranked high on A, the rare antisocials (with low A) would find it relatively easy to steal from their warm-hearted neighbors. These stolen resources would allow the antisocials to have more children, who would, in turn, inherit gene variants that favor low A. But as the number of antisocials increased, their high-A neighbors might band together, mount defenses to protect their resources, and turn back this growing tide. As these forces came into a stable balance over many generations, the result might be a group with a few crafty antisocials
and a majority of members with a range of higher rankings on A.
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The Grandeur in This View of Personality Differences

The realization that human psychological diversity reflects conflicting forces of natural selection has profound implications for making sense of people. But many remain reluctant to embrace this idea because it confronts us with our primitive animal nature. Darwin himself struggled with the seemingly anti-humanistic implications of his discoveries. Nevertheless, being unable to dismiss the evidence in favor of natural selection, he eventually came to see evolution as awe-inspiring. As he explained in
Origin’
s famous last sentence: “There is grandeur in this view of life ... that ... from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

To me, recognizing the role that natural selection of gene variants played in many of our personality differences is a prime example of the grandeur that comes with such understanding. And as I show in the next chapter, it has opened a way to a deeper analysis of the decades-long process by which each of us gradually develops into a unique person.

Four. Building a Personal Brain

When I was a fledgling psychiatrist, a colleague gave me a tip on how he gets to know a new patient. Early in the first visit he briefly imagines the patient as a ten-year-old child. The point of this exercise is to look past someone’s current troubles and picture the person as still little. Was she shy or popular? Was he a bully or a wimp?

I’ve found this tip useful because it immediately dials up compassion: The image of anyone as a child warms my heart. But it also creates a hunch to explore. Forming an imaginary picture of someone in grade school stimulates me to learn about the development of their personality.

When I got this tip in the 1960s, my limited knowledge of personality development was based on the ideas of Erik Erikson. A psychoanalyst who worked with children, Erikson thought we become ourselves by going through a series of well-defined stages as we progress from the extreme dependence of infancy to the responsibilities of adult life. The early stages seemed most important to him because he believed that they leave particularly enduring residues. As he explained in
Childhood and Society
:

Every adult ... was once a child. He was once small. A sense of smallness forms a substratum in his mind, ineradicably. His triumphs will be measured against this smallness, his defeats will substantiate it. The questions as to who is bigger and who can do or not do this or that, and to whom—these questions fill the adult’s inner life far beyond the necessities and the desirabilities which he understands and for which he plans.
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Erikson’s view of personality is appealing because he reminds us of the lasting influence of childhood events. But two things are missing: genes and the brain. When Erikson wrote about the development of individual differences, he assumed that they were mainly due to upbringing and life experiences because very little was known about the influence of genetic variations. And when he described the transitions from one stage to the next, he thought of them primarily as psychological responses to a succession of challenges because very little was known about what was going on in the maturing brain.

This has changed. We now know a great deal about the way our brains develop under the guidance of our personal gene variants and our personal environments. Instead of just thinking of ourselves as solving the challenges of our youth with the brain we were born with, we have come to realize that each brain—like each face—has its own innate building plans. Furthermore, the brain’s building plan was not drafted by the systematic methods of professional architects. Instead, each brain uses a scheme that would drive contractors crazy, with continuous remodeling due to changes in
both genetic and environmental instructions while the project is still underway.

This continuous remodeling has a purpose. By remaining open to the interactions of our unique set of genes and environments during the more than two decades of basic construction, we each come to have a truly personal brain. Within it are the deeply ingrained components of our unique personalities that continue to guide us for the rest of our lives.

The Brain Builds Itself

The adult human brain is built of about 100 billion nerve cells (neurons), most of which were made before we were born. But not all of these neurons were created equal. As the fertilized human egg divides, it generates many types of primitive neurons, each of which is destined to play a particular role in the brain. Having been assigned their approximate fates by a process that turns on and off specific genes, the primitive neurons migrate to their designated places guided by chemical signals that they selectively respond to. When they get there, they start building connections with other neurons to form the neuronal circuits and networks that are the basis of all our behavior.

To build these connections, the neurons make branches called dendrites to receive signals and other branches called axons to send signals. Dendrites are short and studded with spines. Axons can be long enough to reach other neurons anywhere in the brain and to embrace them with clusters of little nerve endings, called boutons. Signaling between boutons of one neuron and dendrites of another occurs at structures called synapses.

A synapse is activated when a bouton releases a chemical neurotransmitter such as serotonin or dopamine onto the spine of a dendrite. The neurotransmitter travels across the synapse and binds to receptors embedded on the spine. This transmits information to the dendrite, a process called synaptic signaling or synaptic transmission.

Many types of synaptic signaling exist between neurons, governed by the dozens of different chemical neurotransmitters that are squirted from boutons onto receptors on the spines. Every neuron manufactures a particular neurotransmitter and displays a particular set of receptors. So every neuron has both a spatial address, defined by its location in a particular brain circuit, and a chemical signature, defined by its neurotransmitter and receptors.

The complicated process of spatial assembly of neurons into circuits and networks is well on its way by the time a person is born. Among the circuits that operate in infancy are some in the amygdala, a brain structure that I mentioned in discussing the SERT gene. The amygdala is a hub for a complex set of circuits that integrate our emotions. Using these infantile circuits, babies experience joy, contentment, fear, anger, and the distress of separation. Neuronal controls of these emotions are gradually put in place over the next two decades, and they have major effects on the developing personality.

Circuit maturation doesn’t depend only on adding new synaptic connections. While useful ones are strengthened, others are eliminated. The same selective remodeling process is also applied to the neurons themselves. Some of them
grow and sprout more branches; others are destroyed by a specialized mechanism of cell death called apoptosis, which is an indispensable part of the developmental process. Much of this happens in fetal life and during the first few years after birth, but some goes on through adolescence and into adulthood.

A notable case of remodeling occurs in a group of neurons in the hypothalamus that play an essential role in the establishment of female or male patterns of sexual behavior. In the female fetus, these neurons die off as part of the developmental program that sets up female-specific sexual circuits. But in the male fetus, testosterone from the fetal testicles rescues these neurons from the apoptotic grim reaper and stimulates them to build male-specific brain circuits.
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The timing of this effect of testosterone is crucial. If it comes too late in fetal development, the key neurons in the hypothalamus are already dead, and the brain is set on an irreversible female course. Other regulators of neuronal death may also have decisive behavioral effects, but none is as obvious as testosterone.

Brain circuits can also be modified by progressively wrapping axons with a fatty substance called myelin. Myelin acts like the insulation around an electrical cord, which facilitates the speed of conduction of electrical signals. Myelination is often a final and essential step in the genetically controlled development of a circuit.

Although this overall developmental program is at work in all of us, each of our brains is different because their structural details are influenced by thousands of gene variants in
our personal genomes. There is also a little sloppiness in the assembly process, due to random variations in the movement of neurons and in the expression of critical genes. This is one reason that even the brains of identical twins are not exactly the same.
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Understanding the step-by step nature of brain construction explains why it is so difficult to go back and make changes in brain circuitry and in the aspects of personality that the circuits control. Once neurons have taken up their positions, they are pretty well settled. Once they have established useful connections, those connections tend to be maintained. Although there is always some residual capacity for change, it takes a lot of work to remodel structures that are built by a developmental program that unfolds over more than two decades. Even our extraordinary human ability to learn new things may not be up to the challenge of modifying patterns that were laid down in this way. This is true not only of patterns that were strongly influenced by genes. It is equally true of those patterns that were shaped by our personal environments during phases of brain development called critical periods.