Personality Theory:
A Biosocial Approach

C. George Boeree, PhD
Psychology Department
Shippensburg University

© Copyright C. George Boeree 2009



Temperaments

Temperaments are personality traits that are rooted in genetics. So, in order to talk about temperaments, we first need to talk about traits.  Traits are the characteristics that make each of us different from others.  When most people talk about personality, they are talking about these traits.  Many of these traits are recognizable by their effects on you behavior.  If you have certain consistent behaviors that others recognize, they often infer that you have a certain personality - i.e. a trait - that you will carry around with you into other situations.

Gordon Allport was a psychologist who was one of the first to pay a great deal of attention to these traits, which he called personal dispositions.  A personal disposition produces equivalences in function and meaning between various perceptions, beliefs, feelings, and actions that are not necessarily equivalent in the natural world, or in anyone else’s mind.  To use one of Allport's own examples, a person with the personal disposition “fear of communism” may equate Russians, liberals, professors, strikers, social activists, environmentalists, feminists, and so on.  He may lump them all together and respond to any of them with a set of behaviors that express his fear:  making speeches, writing letters, voting, arming himself, getting angry, etc.

Allport emphasized that traits are essentially unique to each individual:  One person’s “fear of communism” is not the same as another's, my "introversion" is not the same as yours, his "paranoia" is not the same as hers, etc.  For this reason, Allport strongly pushed what he called idiographic methods - methods that focused on studying one person at a time, such as interviews, observation, analysis of letters or diaries, and so on.

Allport does recognize that within any particular culture, there are common traits, ones that are a part of that culture, that everyone in that culture recognizes and names.  In our culture, we commonly differentiate between introverts and extraverts or liberals and conservatives, and we all know (roughly) what we mean.  But another culture may not recognize these.  What, for example, would liberal and conservative mean in the middle ages?

Allport recognizes that some traits are more closely tied to one’s self than others.  Central traits are the building blocks of your personality, your core constructs.  When you describe someone, you are likely to use words that refer to these central traits:  smart, dumb, wild, shy, sneaky, dopey, grumpy....  He noted that most people have somewhere between five and ten of these.

There are also secondary traits, ones that aren’t quite so obvious, or so general, or so consistent.  Preferences, attitudes, situational traits are all secondary.   For example, “he gets angry when you try to tickle him,” “she has some very unusual sexual inclinations,” and “you just can’t take him out to restaurants.”

But then there are cardinal traits.  These are the traits that some people have which practically define their life.  Someone who spends their life seeking fame, or fortune, or sex is such a person.  Often we use specific historical or fictional people to name these cardinal traits:  Scrooge (greed), Joan of Arc (heroic self-sacrifice), Mother Teresa (religious service), Marquis de Sade (sadism), Machiavelli (political ruthlessness), and so on.  Relatively few people develop a cardinal trait.

Temperaments are central traits that are believed to be genetically based and therefore present from birth or even before.  That does not mean that a temperament theory says we don't also have aspects of our personality that are learned!  Temperament theorists have a focus on "nature," and leave "nurture" to other theorists!

Ancient Greeks

The issue of personality types, including temperament, is as old as psychology.  In fact, it is a good deal older.  The ancient Greeks, to take the obvious example, had given it considerable thought, and came up with two dimensions of temperament, leading to four “types,” based on what kind of fluids (called humors) they had too much or too little of.  This theory became popular during the middle ages.

The sanguine type is cheerful and optimistic, pleasant to be with, comfortable with his or her work.  According to the Greeks, the sanguine type has a particularly abundant supply of blood (hence the name sanguine, from sanguis, Latin for blood) and so also is characterized by a healthful look, including rosy cheeks.

The choleric type is characterized by a quick, hot temper, often an aggressive nature.  The name refers to bile (a chemical that is excreted by the gall bladder to aid in digestion).  Physical features of the choleric person include a yellowish complexion and tense muscles.

Next, we have the phlegmatic temperament.  These people are characterized by their slowness, laziness, and dullness.  The name obviously comes from the word phlegm, which is the mucus we bring up from our lungs when we have a cold or lung infection.  Physically, these people are thought to be kind of cold, and shaking hands with one is like shaking hands with a fish.

Finally, there’s the melancholy temperament.  These people tend to be sad, even depressed, and take a pessimistic view of the world. The name has, of course, been adopted as a synonym for sadness, but comes from the Greek words for black bile.  Now, since there is no such thing, we don’t quite know what the ancient Greeks were referring to.  But the melancholy person was thought to have too much of it!

These four types are actually the corners of two dissecting lines: temperature and humidity.  Sanguine people are warm and wet.  Choleric people are warm and dry.  Phlegmatic people are cool and wet.  Melancholy people are cool and dry.  There were even theories suggesting that different climates were related to different types, so that Italians (warm and moist) were sanguine, Arabs (hot and dry) were choleric, Russians (cold and dry) were melancholy, and Englishmen (cool and humid) were phlegmatic!

What might surprise you is that this theory, based on so little, has actually had an influence on several modern theorists.  Adler, for example, related these types to his four personalities.  But, more to the point, Ivan Pavlov, of classical conditioning fame, used the humors to describe his dogs’ personalities.

One of the things Pavlov tried with his dogs was conflicting conditioning -- ringing a bell that signaled food at the same time as another bell that signaled the end of the meal.  Some dogs took it well, and maintain their cheerfulness.  Some got angry and barked like crazy.  Some just laid down and fell asleep.  And some whimpered and whined and seemed to have a nervous breakdown.  I don’t need to tell you which dog is which temperament!

Pavlov believed that he could account for these personality types with two dimensions:  On the one hand there is the overall level of arousal (called excitation) that the dogs’ brains had available.  On the other, there was the ability the dogs’ brains had of changing their level of arousal -- i.e. the level of inhibition that their brains had available.  Lots of arousal, but good inhibition:  sanguine.  Lots of arousal, but poor inhibition:  choleric.  Not much arousal, plus good inhibition:  phlegmatic.  Not much arousal, plus poor inhibition:  melancholy.  Arousal would be analogous to warmth, inhibition analogous to moisture!  This became the inspiration for Hans Eysenck’s theory.

Carl Jung

Carl Jung developed a personality typology that has become so popular that some people don't realize he did anything else! It begins with the distinction between introversion and extroversion. Introverts are people who prefer their internal world of thoughts, feelings, fantasies, dreams, and so on, while extroverts prefer the external world of things and people and activities.

The words have become confused with ideas like shyness and sociability, partially because introverts tend to be shy and extroverts tend to be sociable. But Jung intended for them to refer more to whether you ("ego") more often faced toward the persona and outer reality, or toward the collective unconscious and its archetypes. In that sense, the introvert is somewhat more mature than the extrovert. Our culture, of course, values the extrovert much more. And Jung warned that we all tend to value our own type most!

We now find the introvert-extravert dimension in several theories, notably Hans Eysenck's, although often hidden under alternative names such as "sociability" and "surgency."

Whether we are introverts or extroverts, we need to deal with the world, inner and outer. And each of us has our preferred ways of dealing with it, ways we are comfortable with and good at. Jung suggests there are four basic ways, or functions:

The first is sensing. Sensing means what it says: getting information by means of the senses. A sensing person is good at looking and listening and generally getting to know the world. Jung called this one of the irrational functions, meaning that it involved perception rather than judging of information.

The second is thinking. Thinking means evaluating information or ideas rationally, logically. Jung called this a rational function, meaning that it involves decision making or judging, rather than simple intake of information.

The third is intuiting. Intuiting is a kind of perception that works outside of the usual conscious processes. It is irrational or perceptual, like sensing, but comes from the complex integration of large amounts of information, rather than simple seeing or hearing. Jung said it was like seeing around corners.

The fourth is feeling. Feeling, like thinking, is a matter of evaluating information, this time by weighing one's overall, emotional response. Jung calls it rational, obviously not in the usual sense of the word.

We all have these functions. We just have them in different proportions, you might say. Each of us has a superior function, which we prefer and which is best developed in us, a secondary function, which we are aware of and use in support of our superior function, a tertiary function, which is only slightly less developed but not terribly conscious, and an inferior function, which is poorly developed and so unconscious that we might deny its existence in ourselves.

Most of us develop only one or two of the functions, but our goal should be to develop all four. Once again, Jung sees the transcendence of opposites as the ideal.

Katharine Briggs and her daughter Isabel Briggs Myers found Jung's types and functions so revealing of people's personalities that they decided to develop a paper-and-pencil test. It came to be called the Myers-Briggs Type Indicator, and is one of the most popular, and most studied, tests around.

On the basis of your answers on about 125 questions, you are placed in one of sixteen types, with the understanding that some people might find themselves somewhere between two or three types. What type you are says quite a bit about you -- your likes and dislikes, your likely career choices, your compatibility with others, and so on. People tend to like it quite a bit. It has the unusual quality among personality tests of not being too judgmental: None of the types is terribly negative, nor are any overly positive. Rather than assessing how "crazy" you are, the "Myers-Briggs" simply opens up your personality for exploration.

The test has four scales. Extroversion - Introversion (E-I) is the most important. Test researchers have found that about 75% of the population is extroverted.

The next one is Sensing - Intuiting (S-N), with about 75% of the population sensing.

The next is Thinking - Feeling (T-F). Although these are distributed evenly through the population, researchers have found that two-thirds of men are thinkers, while two-thirds of women are feelers. This might seem like stereotyping, but keep in mind that feeling and thinking are both valued equally by Jungians, and that one-third of men are feelers and one-third of women are thinkers. Note, though, that society does value thinking and feeling differently, and that feeling men and thinking women often have difficulties dealing with people's stereotyped expectations.

The last is Judging - Perceiving (J-P), not one of Jung's original dimensions. Myers and Briggs included this one in order to help determine which of a person's functions is superior. Generally, judging people are more careful, perhaps inhibited, in their lives. Perceiving people tend to be more spontaneous, sometimes careless. If you are an extrovert and a "J," you are a thinker or feeler, whichever is stronger. Extroverted and "P" means you are a senser or intuiter. On the other hand, an introvert with a high "J" score will be a senser or intuiter, while an introvert with a high "P" score will be a thinker or feeler. J and P are equally distributed in the population.

Each type is identified by four letters, such as ENFJ. These have proven so popular, you can even find them on people's license plates!

However useful and popular Jung's system is, it is primarily based on one man's observations. The next step is to try and do what Jung did with a bit more scientific precision.  That's were Hans Eysenck comes in.

Hans Eysenck

Eysenck’s theory is  based primarily on physiology and genetics.  Although he is a behaviorist who considers learned habits of great importance, he considers personality differences as growing out of our genetic inheritance.  He is, therefore, primarily interested in what is usually called temperament.

Eysenck is also primarily a research psychologist.  His methods involve a statistical technique called factor analysis.  This technique extracts a number of “dimensions” from large masses of data.  For example, if you give long lists of adjectives to a large number of people for them to rate themselves on, you have prime raw material for factor analysis.

Imagine, for example, a test that included words like “shy,” “introverted,” “outgoing,” “wild,” and so on. Obviously, shy people are likely to rate themselves high on the first two words, and low on the second two. Outgoing people are likely to do the reverse. Factor analysis extracts dimensions -- factors -- such as shy-outgoing from the mass of information.  The researcher then examines the data and gives the factor a name such as “introversion-extraversion.” There are other techniques that will find the “best fit” of the data to various possible dimension, and others still that will find “higher level” dimensions -- factors that organize the factors, like big headings organize little headings.

Eysenck's original research found two main dimensions of temperament: neuroticism and extraversion-introversion.  Let’s look at each one...

Neuroticism is the name Eysenck gave to a dimension that ranges from normal, fairly calm and collected people to one’s that tend to be quite “nervous.”  His research showed that these nervous people tended to suffer more frequently from a variety of “nervous disorders” we call neuroses, hence the name of the dimension. But understand that he was not saying that people who score high on the neuroticism scale are necessarily neurotics -- only that they are more susceptible to neurotic problems.

Eysenck was convinced that, since everyone in his data-pool fit somewhere on this dimension of normality-to-neuroticism, this was a true temperament, i.e. that this was a genetically-based, physiologically-supported dimension of personality. He therefore went to the physiological research to find possible explanations.

The most obvious place to look was at the sympathetic nervous system.  This is a part of the autonomic nervous system that functions separately from the central nervous system and controls much of our emotional responsiveness to emergency situations.  For example, when signals from the brain tell it to do so, the sympathetic nervous systems instructs the liver to release sugar for energy, causes the digestive system to slow down, opens up the pupils, raises the hairs on your body (goosebumps), and tells the adrenal glands to release more adrenalin (epinephrine). The adrenalin in turn alters many of the body’s functions and prepares the muscles for action. The traditional way of describing the function of the sympathetic nervous system is to say that it prepares us for “fight or flight.”

Eysenck hypothesized that some people have a more responsive sympathetic nervous system than others. Some people remain very calm during emergencies; some people feel considerable fear or other emotions; and some are terrified by even very minor incidents.  He suggested that this latter group had a problem of sympathetic hyperactivity, which made them prime candidates for the various neurotic disorders.

Perhaps the most “archetypal” neurotic symptom is the panic attack. Eysenck explained panic attacks as something like the positive feedback you get when you place a microphone too close to a speaker: The small sounds entering the mike get amplified and come out of the speaker, and go into the mike, get amplified again, and come out of the speaker again, and so on, round and round, until you get the famous squeal that we all loved to produce when we were kids. (Lead guitarists like to do this too to make some of their long, wailing sounds.)

Well, the panic attack follows the same pattern: You are mildly frightened by something -- crossing a bridge, for example. This gets your sympathetic nervous system going. That makes you more nervous, and so more susceptible to stimulation, which gets your system even more in an uproar, which makes you more nervous and more susceptible....  You could say that the neuroticistic person is responding more to his or her own panic than to the original object of fear!  As someone who has had panic attacks, I can vouch for Eysenck’s description -- although his explanation remains only a hypothesis.

His second dimension is extraversion-introversion. By this he means something very similar to what Jung meant by the same terms, and something very similar to our common-sense understanding of them: Shy, quiet people “versus” out-going, even loud people. This dimension, too, is found in everyone, but the physiological explanation is a bit more complex.

Eysenck hypothesized that extraversion-introversion is a matter of the balance of “inhibition” and “excitation” in the brain itself.  These are ideas that Pavlov came up with to explain some of the differences he found in the reactions of his various dogs to stress.  Excitation is the brain waking itself up, getting into an alert, learning state. Inhibition is the brain calming itself down, either in the usual sense of relaxing and going to sleep, or in the sense of protecting itself in the case of overwhelming stimulation.

Someone who is extraverted, he hypothesized, has good, strong inhibition: When confronted by traumatic stimulation -- such as a car crash -- the extravert’s brain inhibits itself, which means that it becomes “numb,” you might say, to the trauma, and therefore will remember very little of what happened. After the car crash, the extravert might feel as if he had “blanked out” during the event, and may ask others to fill them in on what happened.  Because they don’t feel the full mental impact of the crash, they may be ready to go back to driving the very next day.

The introvert, on the other hand, has poor or weak inhibition: When trauma, such as the car crash, hits them, their brains don’t protect them fast enough, don’t in any way shut down.  Instead, they are highly alert and learn well, and so remember everything that happened.  They might even report that they saw the whole crash “in slow motion!”  They are very unlikely to want to drive anytime soon after the crash, and may even stop driving altogether.

Now, how does this lead to shyness or a love of parties?  Well, imagine the extravert and the introvert both getting drunk, taking off their clothes, and dancing buck naked on a restaurant table. The next morning, the extravert will ask you what happened (and where are his clothes). When you tell him, he’ll laugh and start making arrangements to have another party. The introvert, on the other hand, will remember every mortifying moment of his humiliation, and may never come out of his room again. (I’m very introverted, and again I can vouch to a lot of this experientially! Perhaps some of you extraverts can tell me if he describes your experiences well, too -- assuming, of course, that you can remember you experiences!)

One of the things that Eysenck discovered was that violent criminals tend to be non-neuroticistic extraverts. This makes common sense, if you think about it: It is hard to imagine somebody who is painfully shy and who remembers their experiences and learns from them holding up a Seven-Eleven! It is even harder to imagine someone given to panic attacks doing so. But please understand that there are many kinds of crime besides the violent kind that introverts and neurotics might engage in!

Another thing Eysenck looked into was the interaction of the two dimensions and what that might mean in regard to various psychological problems.  He found, for example, that people with phobias and obsessive-compulsive disorder tended to be quite introverted, whereas people with conversion disorders (e.g. hysterical paralysis) or dissociative disorders (e.g. amnesia) tended to be more extraverted.

Here’s his explanation: Highly neuroticistic people over-respond to fearful stimuli; If they are introverts, they will learn to avoid the situations that cause panic very quickly and very thoroughly, even to the point of becoming panicky at small symbols of those situations -- they will develop phobias. Other introverts will learn (quickly and thoroughly) particular behaviors that hold off their panic -- such as checking things many times over or washing their hands again and again.

Highly neuroticistic extraverts, on the other hand, are good at ignoring and forgetting the things that overwhelm them.  They engage in the classic defense mechanisms, such as denial and repression. They can conveniently forget a painful weekend, for example, or even “forget” their ability to feel and use their legs.

Eysenck came to recognize that, although he was using large populations for his research, there were some populations he was not tapping. He began to take his studies into the mental institutions of England. When these masses of data were factor analyzed, a third significant factor began to emerge, which he labeled psychoticism.

Like neuroticism, high psychoticism does not mean you are psychotic or doomed to become so -- only that you exhibit some qualities commonly found among psychotics, and that you may be more susceptible, given certain environments, to becoming psychotic.

As you might imagine, the kinds of qualities found in high psychoticistic people include a certain recklessness, a disregard for common sense or conventions, and a degree of inappropriate emotional expression. It is the dimension that separates those people who end up institutions from the rest of humanity!

Baby temperaments

Arnold Buss (b. 1924) and Robert Plomin (b. 1948), both working at the University of Colorado at the time, took a different approach:  If some aspect of our behavior or personality is supposed to have a genetic, inborn basis, we should find it more clearly in infants than in adults.

So Buss and Plomin decided to study infants.  Plus, since identical twins have the same genetic inheritance, we should see them sharing any genetically based aspects of personality.  If we compare identical twins with fraternal twins (who are simply brothers or sisters, genetically speaking), we can pick out things that are more likely genetic from things that are more likely due to the learning babies do in their first few months.

Buss and Plomin asked mothers of twin babies to fill out questionnaires about their babies’ behavior and personality.  Some babies were identical and others fraternal.  Using statistical techniques similar to factor analysis, they separated out which descriptions were more likely genetic from which were more likely learned.  They found four dimensions of temperament:

1.  Emotionality-impassiveness:  How emotional and excitable were the babies?  Some were given to emotional outbursts of distress, fear, and anger -- others were not.  This was their strongest temperament dimension.

2.  Sociability-detachment:  How much did the babies enjoy, or avoid, contact and interaction with people.  Some babies are “people people,” others are “loners.”

3.  Activity-lethargy:  How vigorous, how active, how energetic were the babies?  Just like adults, some babies are always on the move, fidgety, busy -- and some are not.

4.  Impulsivity-deliberateness:  How quickly did the babies “change gears,” move from one interest to another?  Some people quickly act upon their urges, others are more careful and deliberate.

The last one is the weakest of the four, and in the original research showed up only in boys.  That doesn’t mean girls can’t be impulsive or deliberate -- only that they seemed to learn their style, while boys seem to come one way or the other straight from the womb.  But their later research found the dimension in girls as well, just not quite so strongly.  It is interesting that impulse problem such as hyperactivity and attention deficit are more common among boys than girls, as if to show that, while most girls can be taught to sit still and pay attention, many boys cannot.

The big five

In the last couple of decades, an increasing number of theorists and researchers have come to the conclusion that five is the “magic number” for temperament dimensions.  The first version, called The Big Five, was introduced in 1963 by Warren Norman.  It was a fresh reworking of an Air Force technical report by E. C. Tuppes and R. E. Christal.

But it wasn’t until R. R. McCrae and P. T. Costa, Jr., presented their version, called The Five Factor Theory, in 1990, that the idea really took hold of the individual differences research community.  When they introduced the NEO Personality Inventory, many people felt, and continue to feel, that we’d finally hit the motherload!

Here are the five factors, and some defining adjectives:

1.  Extraversion - adventurous, assertive, frank, sociable, talkative (versus Introversion - quiet, reserved, shy, unsociable).

2.  Agreeableness - altruistic, gentle, kind, sympathetic, warm.

3.  Conscientiousness - competent, dutiful, orderly, responsible, thorough.

4.  Emotional Stability  - calm, relaxed, stable (versus Neuroticism - anxious, angry, depressed).

5.  Culture or Openness to Experience - cultured, esthetic, imaginative, intellectual, open.

Temperaments could only be called temperaments if they are stable over time, that is, resistant to environmental issues.  Costa and McCrae (1994) found the following correlations between tests over six years:

Neuroticism - .83
Extraversion - .82
Openness - .83
Conscientiousness - .79
Agreeableness - .63

Pretty powerful!  Looking at other studies, some of which stretched for 30 years, they found about .50 corrrelations.  Still good!

The Dunedin Study by Caspi and his associates (2003) did a particularly strong study (in Dunedin, New Zealand) that looked at the change in traits of 1000 kids over 23 years and found considerable stability.  The most stable were two groups, which they called "undercontrolled", which Costa and McCrae might consider high in neuroticism but low in agreeableness and conscientiousness, and "inhibited" (low extraversion).

In a great book by Dunn and Plomin (1990) called Separate lives: Why siblings are so different, the issue of "heritability" is discussed at length.  Heritability, as you may have guessed, is the degree of the variance in personality traits that can be accounted for by heredity.  It turns out to be about 40%.  But what accounts for the other 60%?  One would assume upbringing.  But that turns out to be wrong!  Instead, most of that 60% is accounted for by individual experience not shared with your siblings.  Dunn and Plomin estimate that 40% of your personality is due to genetics, 35% to this "non-shared" environment, 20% to measurement error, and only 5% to the shared environment (upbringing).  This is surprising, but it doesn't mean that your personality is determined by genetics.  An equal amount is due to learning, except most of the learning is more individual than expected.

As you can see, while temperaments have staying power, they do change over time.  Costa and McCrae (1994) also found that Extraversion, Neuroticism, and Openness tend to decline as we get older.  We become a little quieter, you might say, and stuck in our ways.  Agreeableness and Conscientiousness tend to go up - we learn how to get along with others and how to get things done.  But they don't change very much.  Really, we learn how to use our personality in the life that is given to us.

At this point in time, the Big Five is the "gold standard" for personality research.  Versions of these tests are now available free on the internet in order that researchers all over the world can coordinate their research.  But there are still other factors which we need to take into account as possible temperaments.  The most important of these is intelligence.

Intelligence

Another viable candidate for status as a quality of temperament is intelligence.  Intelligence is a person's capacity to (1) acquire knowledge (i.e. learn and understand), (2) apply knowledge (solve problems), and (3) engage in abstract reasoning.  It is the "power" of one's intellect, and as such is clearly a very important aspect of one's overall well-being.  Psychologists have attempted to measure it for well over a century, and have gotten pretty good at it..

Intelligence Quotient (IQ) is the score you get on an intelligence test. Originally, it was a quotient (a ratio):  IQ= MA/CA x 100 [MA is mental age, CA is chronological age]. Today, scores are calibrated against norms of actual population scores.  Here are approximate proportions at various levels:

Under 70 [mentally retarded] - 2.2%
70-80 [borderline retarded] - 6.7%
80-90 [low average] - 16.1%
90-110 [average] - 50%
110-120 [high average] - 16.1%
120-130 [superior] - 6.7%
Over 130 [very superior] - 2.2%

Intelligence is significantly genetic.  The correlation in IQ scores between mother and child, father and child, and between two natural siblings is approximately .50, which is what we would expect, since you share half your genetic materials with your parents, children, and siblings.  Likewise, correlation between parents and their adopted children is rougly 0.

But we can also see a number of environmental aspects to intelligence:  A stimulating environment, parental encouragement, good schooling, specific reasoning skills, continued practice, and so on, certainly help a person become more intelligent.  Likewise, there are certain biological factors that are nevertheless environmental:  prenatal care, nutrition (especially in early childhood), freedom from disease and physical trauma, and so on.  All of these are important and cannot be ignored - especially when these are the things we can most easily do something about! 

I believe that something better than half of intelligence is accounted for by genetics.  And this is, to put it simply, a matter of brain efficiency.  If your brain is well-developed, free from genetic defects, free from neurochemical imbalances, then it will work well, given a decent environment.  But no matter how good your environment, if you are forced to rely on “bad equipment,” it will be much more difficult to attain high intelligence.

Most of the normal curve of intelligence, I believe, is due to a variety of physiological impairments of brain efficiency, such as that resulting from malnourishment, prenatal trauma, chromosomal damage, and, most often, simple inheritance of certain neurochemical makeups.  These stretch what would otherwise be a much “tighter” curve out to the low end.

The great majority of us have fairly healthy brains.  A very few have particularly healthy brains.  It would seem that having particularly healthy brains would be a fantastic aid to one’s “fitness,” so I can only guess that not being too bright must be even better!

Maleness and femaleness

After a few millenia of sexism, we are rightfully wary of ideas that suggest that men and women may be psychologically different from each other.  And yet we can't get away from the evidence that we do have some differences, and that these differences are tied to our physiological differences.  Even if we stick simply to hormonal differences, we have to recognize that the sex hormones do make us behave differently in certain circumstances.  On top of that, we are coming to recognize some physiological differences between homosexuals and heterosexuals.  So, while I fervently hope that I do imply value differences with my discussion of male-female (and homosexual-heterosexual) personality traits, I must sally forth!

The psychological differences between men and women revolve around our biological roles and the instincts we have to carry out those roles.  Men, as with so many mammalian males, appear to be significantly more aggressive than women.  This is probably related to our evolutionary need to compete with other men for the attention of women.  That competition has led to men being larger and more muscular and, of course, loaded with that most irritating hormone, testosterone.  The size and strength of men in relation to women has led to the gender-specific roles in primitive society:  men are more likely to engage in the short-burst high-energy tasks such as hunting, while the women engage in less intense but far more extended tasks such as gathering.  Unfortunately, the size and strength differential has also lead to most societies being dominated by men, often with women relegated to a slave-like social status.

Women have strong ties to infants, which could be accounted for by the fact that they carry the fetus for 40 weeks and then nurse the baby for two or three years (at least in primitive cultures), all strongly supported by hormone-mediated instincts.  Again, in primitive societies, the woman is either pregant, nursing, or caring for her children continuously.  This makes her even more likely to restrict her other activities to gathering, cooking, and other home-bound pursuits.  It also makes her more likely to be dominated by men.  It also makes her (and her family) far more concerned about an appropriate mate than would be the men.

The overall effects on men's and women's psychological natures are still evident today, despite the slow movement towards social equality.  Men are still far more likely to act on their aggressive impulses and commit violent crimes.  They are more likely to attack than to retreat.  They engage in more high-risk activities. They are more likely to seek multiple partners.  They are more likely to abandon their children.

Women, on the other hand, are more likely to retreat than to attack, and tend to show emotion more dramatically.  They tend to prefer nurturant acitivities to competitive ones, even as children.  They seek more same-sex companionship than men.  They talk more, and are more fluent than men.  (Note that in mixed groups, men talk more because they are more assertive, while women tend to back off in order to maintain order in the group.)  And they are more likely to continue in a relationship, even if only "for the sake of the children".

Again, please keep in mind that we are talking about overall tendencies.  Many women are aggressive, for example, and many men are nurturant.  Some of the things I mentioned as differences may be due more to cultural learning, or at least be reinforced by cultural learning, than I suggest, and so may change dramatically in the future.

The big question for personality theory here is whether maleness-femaleness is a fundamental dimension, or is just a composite of some of the other dimensions we've discussed here.  I vote for fundamental, but I have been known to be wrong!

Autism

Another possible temperament factor is autism.  Autism is a pervasive developmental disorder that causes children to have a great deal of difficulty interacting with other people.  It can be so severe that the child will not make eye-contact, not respond to their name, not learn to talk, and spend much of their day rocking or doing other repetitive things like rolling a ball back and forth or spinning coins.  Obviously hard on the children, it is even harder for their families.

The causes of autism are still not known.  It is believed by most researchers that it involves problems with neural circuits, and twin studies suggest that genetic influences are likely.  For a long time, it was incorrectly believed that autism resulted from parental neglect.

The usual approach to helping children with autism is to use rewards to encourage social interaction, try to develop their language skills, and lead them to some degree of self-care. Some children respond very well and go on to support themselves. Others remain in a state that requires care for the rest of their lives.

There has been some limited success with antipsychotic drugs and with antidepressants.

In the last 20 years or so, a number of finer differentiations have evolved regarding what is now seen as an autistic spectrum.

First, we have something called Asperger's syndrome.  These children (and adults) are generally of normal (and sometimes high) intelligence, but have difficulty in social interaction.  They seem exceptionally shy and have a hard time making eye contact. They have trouble learning  what is called pragmatics -- the part of communication between people that involves recognizing turn-taking, facial expressions, gestures, and other non-verbal cues.  They tend to focus intensely on one thing at a time, don't like abrupt changes, and develop obsessive routines.  As adults, they usually adapt, but are seen as being socially inept, absent minded, and eccentric.  Of course, that begs the question a little:  Is this truly a separate disorder, or just a little out there on the continuum of normal behavior?

There are other syndromes that focus more on language:  The semantic-pragmatic disorder is sometimes used to label certain children who are similar to Asperger's children but more sociable.  The focus of their problem is more on the communications side.

Hyperlexia is more a symptom than a disorder.  It is a matter of being rather precocious in reading words, and being fascinated by letters and numbers.  On the other hand, children with hyperlexia don't communicate well, nor do they socialize well.

Non-verbal learning disability is a matter of having a hard time with visual, spatial, and motor skills.  They have a hard time picking out, say, one house out of a row of them, tying their shoes, getting dressed, kicking a ball, reading facial expressions, and recognizing the tone of someone's voice.  One of the notable symptoms is the tendency to stare, especially when visually over-stimulated.

A related problem that is close to my heart (because I have a mild version of this) is prosopagnosia or face blindness.  This affects about 2 1/2 % of the population, and people with this problem have a difficult time recognizing faces.  It can be so severe that a man can walk past his own mother and not recognize her!  Generally, people with this problem develop other ways of recognizing people, such as clothing or hair styles.  I recognize people I have known for a long time, but cannot place less familiar people out of the context  of, say, a specific classroom or circumstance.  It makes one seem rude, but it is unintentional.  Interestingly, people with prosopagnosia often also have a hard time identifying some other things, such as dogs and cars!  It is believed to be a problem involving the fusiform gyrus, which is involved in facial recognition.

Where does autism fit with the other personality traits we have been discussing?  It is not clear.  One possibility is that it is related to psychoticism, with its detachment from reality.  Another is that it is a variation of introversion, with its withdrawal from social interaction.  It may be a combination of these, or others, or it may be in a category of its own.

Antisociality

Another group of temperament issues revolve around the lack of conscience we find in some people: an inability to empathize with others, an absense of guilt.  We might call these problems "antisociality" as opposed to the autistic spectrums "unsociability."  There are three disorders that often involve this syndrome: conduct disorder in children, and borderline and antisocial personality disorders in adults.

Conduct disorder. 

Here's what the Surgeon General's report has to say:

Children or adolescents with conduct disorder behave aggressively by fighting, bullying, intimidating, physically assaulting, sexually coercing, and/or being cruel to people or animals. Vandalism with deliberate destruction of property, for example, setting fires or smashing windows, is common, as are theft; truancy; and early tobacco, alcohol, and substance use and abuse; and precocious sexual activity. Girls with a conduct disorder are prone to running away from home and may become involved in prostitution. The behavior interferes with performance at school or work, so that individuals with this disorder rarely perform at the level predicted by their IQ or age. Their relationships with peers and adults are often poor. They have higher injury rates and are prone to school expulsion and problems with the law. Sexually transmitted diseases are common. If they have been removed from home, they may have difficulty staying in an adoptive or foster family or group home, and this may further complicate their development. Rates of depression, suicidal thoughts, suicide attempts, and suicide itself are all higher in children diagnosed with a conduct disorder (Shaffer et al., 1996b).
There have been many studies of conduct disorder, with many, sometimes contradictory results.  There seems to be a genetic component, which is why I include it here; but it also has a number of social risk factors, such are a lack of love from parents or caretakers, neglect, abuse, poverty, and other family problems.  Other possible roots include prenatal problems, birth complications, and brain damage.

Among children from 9 to 17, we find between 1 and 4 percent showing evidence of conduct disorder, and the problem being worse in the cities.  There is a correlation between the bad behavior of 3-year-olds and their bad behavior when they are 11 to 13 (Raine et al., 1998). Between 25 and 50% of these children are believed to develop into antisocial adults.

Treatment of children with conduct disorder tends to focus on making their family lives happier and more consistent.  If the parents or other caretakers are responsive, there are programs that teach them how to use rewards and punishments more effectively.  For many of these kids, it is a matter of trying to find a home for them at all!  Medications have not been found to help.

Borderline personality disorder. 

Borderline people (mostly women) usually have a rather rough time with relationships.  They are very moody, going from cheerful to angry to sad and back to cheerful at a speed few of us can match.  They often seem to worship someone one minute and, an hour later, hate them.  They are often impulsive, getting involved with drugs and alcohol, reckless sexual relationships, spending sprees, and so on.  And they often engage in self-destructive behavior, ranging from speeding to "cutting" (self-mutilation) to suicidal behavior.  They use these things to threaten others into doing what they want.

Borderline personality disorder is so-called because of the belief that it represents a personality style that is close to, but not quite, psychotic.  Many of their symptoms, as you can see, suggest that.  But I have been impressed by the ability to lie and manipulate in borderline people I have known - nearly as well as the antisocials.  Instead of coming off as powerful, they use their weaknesses to manipulate.  And, like antisocials, they appear to feel little if any empathy or guilt.  They pull you towards them, then push you away, then pull you back.  They pit one friend against another.  They dramatize situations to their own ends.  They move, chameleon-like, from one "personality" to another.  Also like the antisocials, they are extremely difficult to treat.  Possibly, they combine some of the issues of antisocial personality disorder with psychosis.  Inasmuch as borderlines are predominantly women, it is also possible that they have followed their cultural guidelines as to traditional male-female differences in behavior, and are antisocials who use more passive means of getting their way.

But it also seems that much of their behavior is self-defeating.  There are signs of dissociation that suggest that borderline personality disorder may be related to some degree to multiple personality or even schizophrenia.  It is more common in people who have a history of neglect, abuse, and family conflict, so both a degree of dissociation and defensive manipulation would be expected.

Antisocial personality disorder 

A pervasive pattern of disregard for and violation of the rights of others occurring since age 15 years, as indicated by three (or more) of the following:

It is believed that something on the order of one in six people (mostly men) have this personality disorder.  I think it is likely to be higher - perhaps 20%.  The antisocial disorder used to be called the sociopath, and before that, the psychopath.  The change in name simply reflects the fact that the public tends to associate the disorder only with the most extreme and dramatic cases, such as serial killers.  But in fact, people with little sense of empathy or guilt live all around us and we hardly notice them until they affect us personally.  If they have a decent level of intelligence, they fully recognize that certain acts are illegal or looked down upon by others, and, since that only makes trouble for themselves, they avoid those things.  In other words, most antisocials are rational.  I believe that, in addition to the violent criminals that may be obviously antisocial, there are also many highly successful antisocials who, in fact, owe their success to the very fact that they don't really care how they get wealth and power, only that they do actually get it.  I have strong suspicions about some of those corporate executives who blithely steal from their employees and stockholders and calmly lie about it when caught.  I also suspect that some of our politicians are sociopaths, especially those that seem to be able to ignore the suffering of the less fortunate while filling their pockets and the pockets of their friends with money, or those who have no qualms about declaring wars that kill and maim thousands of our own young men and women, as well as hundreds of thousands of innocent men, women, and children of the so-called enemy.

No one knows exactly where the antisocial personality disorder comes from, but we do know that many violent criminals have damage to the prefrontal lobes.  Apparently, the prefrontal lobes play a big part in controlling the limbic system, including damping emotions.  In some circumstances, the fear response of the amygdala is dampened, while the rage response is intensified.  If you are very angry but afraid of nothing, you can do a great deal of damage!  Of course the majority of antisocials have not had damage to the prefrontal lobes, and so we can only speculate that perhaps these areas are less well developed than they are in normal people.

Others view antisocial personality disorder as derived from poor upbringing, involving abuse or neglect.  In particular, some believe that it is the result of a lack of love, especially from the mother, which prevents the child from developing the ability to love, or even the ability to recognize the personhood of others.  As with most psychological disorders, it is quite likely that both the physical and the developmental explanations play a part.  One unfortunate aspect of the disorder is that there seems to be no therapy that can touch it.  These people are excellent liars and manipulators, quite capable of convincing their therapists and others that they have reformed, found Jesus, or otherwise bettered themselves.  Many go on to form inspirational groups and write self-help manuals.  But it's really just that they've found another way to use people.

On the other hand, one could also argue that desensitizing oneself to the pain of others and becoming arrogant and self-centered is a matter of survival in some societies.  Like paranoia, it is more likely to develop in egocentric and hierarchical cultures.

Conclusions

Although you may feel a bit overwhelmed with all the various theories, personality theorists in fact are more encouraged than discouraged:  It is fascinating to us that all these different theorists, often coming from very different directions, still manage to come up with very parallel sets of temperament dimensions.

Extraversion - introversion is universally accepted as a temperament.  But we may need to re-evaluate the far ends of this dimension.  First, though extraversion is generally the preferred end, extraversion comes with a price:  extraverts do not learn from their experiences as much as introverts do and so tend to make repeated mistakes, social and physical, that introverts do not make. They also can become needy when it comes to social interaction.  You have no doubt seen the recent phenomenon of the cell-phone addict, who walks around with his or her phone (often with earphones) permanently attached to their ears.  It seems they just cannot do without that constant social contact.  On the introverted side, we might include some of the autistic spectrum disorders, at least in part.  The difficulty that, for example, the Asperger's person has relating to others may be a matter of extreme introversion.

Emotional stability - neuroticism is also universally accepted.  I believe, however, that we really need to re-examine the "stable" end of the dimension.  The neuroticistic end is pretty clear:  A tendency to emotionality, especially anxiety, is clearly in-born, and make high neuroticistic people much more prone, as the name implies, to anxiety disorders and depression.  But isn't there something to be said for some anxiety?  It evolved, no doubt, because being a bit wary can make the difference between life and death!  So, having little or no anxiety or other emotional responses - being to "cool" - has its own problems.  I suspect that people who get involved in high-risk activities do so because they find it more difficult to find excitement in life.  And I have noticed that some criminals (and a few heads of state as well) are exceptionally calm.  Even their eyes have that sleepy look that suggests they never get nervous.  So, I suggest that never getting emotional might be just as problematic as being too emotional.

Agreeableness - disagreeableness is less universally accepted.  Generally, people like agreeable people, which is, of course, why we consider them agreeable.  The negative side of agreeableness is that agreeable people are often also conforming, even obedient, people, uncomfortable with disagreement and controversy.  The disagreeable people, for all their possible lack of tact, at very least speak their minds and are not afraid to disagree.  Agreeable people seem to be very sensitive to the feelings of other, and this end of the dimension sounds very much like Jung's feeling type.  Disagreeable people, perhaps, like Jung's thinking type, have difficulty understanding others, especially their feelings.

Perhaps we can find the asocial disorders at the extreme disagreeable end of this dimension.  In Myers-Briggs based research, men are more likely to be thinking (possibly disagreeable) and women more likely to be feeling (possibly agreeable).  There is some confirmation for this in that conduct disorder in children and antisocial personality disorder in adults include far more men than women.  But the borderline disorder, as I mentioned, is predominantly women, suggesting either that borderline is not a "female" variation of antisocial, or that the asocial traits are not related to disagreeableness.

Conscientiousness - nonconscientiousness is also less accepted.  But it agrees very nicely with Myers and Briggs' traits of judging and perceiving, as well as with Freud's contrast of the anal retentive and anal expulsive.  The latter two have a long history in psychology, and we still use these terms.  The anal retentive is finicky, neat, clean, orderly, and thritfy.  The anal expulsive is easy-going, messy, and relaxed in regards to money.  In Freud's original system, these are not inborn, but the consequence of early and/or harsh potty training and late and/or lackadaisical potty-training.  It is doubtful that these types are due directly to potty training, but a general family atmosphere of cleanliness and orderliness, versus the opposite may very well cause, or at least bring out, these characteristics.  Nevertheless, I (and many others) believe that there is a considerable genetic component to these traits. 

Conscientiousness in its extreme becomes perfectionism.  Combined with neuroticism, it is probably at the root of the obsessive-compulsive disorder.  It is possible that nonconscientiousness is the major contributor to Eysenck's dimension of psychoticism as a kind of involuntary inattentiveness to one's environment.  The early stages of schizophrenia often involve a messy, disorderly lifestyle.

Impulsivity (vs deliberateness) might also be related to conscientiousness - nonconscientiousness (in reverse, of course), but it isn't a precise match.  Impulsivity is certainly related to the problem of attention deficit and hyperactivity (ADHD).  The fact that the antisocial types we discussed earlier often have problems with impulse-control may mean that the antisocial disorders are a combination of nonconscientiousness and disagreeableness.

Openness - conventionality.  The last of the "big five" is openness, or culture, and it is the least robust of the bunch.  First, we might suggest that being "open" is not necessarily a wonderful thing.  We all know some people who are so "open" that they are interested in anything, no matter how trivial, obscure, or even deviant.  "Flakey" is a word that comes to mind.  On the other hand, I would suggest that a good name for the opposite end of openness (rarely discussed) would be the conventional.  This puts the openness dimension in line with Jungs sensing-intuiting distinction (reversed, of course).  Both ends have advantages and disadvantages.

"O" is the most interesting of the traits to me.  First, it has some correlation with intelligence.  For example, McCrae and Costa (1985) found a +.32 correlation - small but significant.  But more interesting is its relationship with ideas usually considered more learned than inherited, such as "liberal v. conservative."  McCrae and Costa (1980) noticed, for example, that typical conservative values such as respect for authority and tradition correlated negatively with openness.

Another connection is a reversed one between openness and authoritarianism.  The basic book on authoritarianism is The Authoritarian Personality by Adorno and his colleagues (1950).  They developed the F-scale (California Fascism Scale).  This test tapped the following qualities:

Conventional values
Strongly punitive reaction to the violation of those values
Overly concerned with deviations from sexual norms
Anti-intellectual attitudes
Rigid categories and tendency to stereotyping
Preoccupation with power and strength
Submission to authority
Hostility to others
Belief that the world is a very dangerous place

These same qualities, in a less extreme form, are typical of conservatism generally.  Trapness (1994) found a -.57 correlation between openness and authoritarianism as measure by the F-scale!

Activity-lethargy.  I don't see a clear connection to the dimensions we have discussed so far, and I suggest that it is a separate dimension, ignored, perhaps, because it is seen as more a physical thing than a psychological one.  Perhaps it doesn't show up as a temperament in adults because adults have been so affected by their environment that the genetic foundations of activity level are hidden.  It could, of course, have some connection to impulsivity and ADHD.  Personally, I think that activity-lethargy is a legitimate temperament that needs to be added to the "big five."

Until further research finally establishes the relationship of these (and potentially other) factors, I suggest that we consider them the "Big Eleven":

Extravert:  People-oriented, talkative.  Prefers the company of people, comfortable with many, uncomfortable with isolation.  Socially daring, not easily embarrassed or shamed. Introvert:  Shy, quiet.  Prefers solitude or the company of no more than a few people.  Easily embarrassed or shamed.
Stable:  Cool, emotionally stable.  Not quick to anger or fear.  Less likely to feel sadness or anxiety.  May even seek intense experiences.
Neuroticistic:  Nervous, emotional, moody.  Easily scared, made angy, or brought to tears.  More likely to develop emotional problems such as anxiety disorders, depression, and anger-control issues.
Conscientious:  Orderly, organized.  Uncomfortable with disorder.  On-time, responsible.  Sometimes obsessive and self-critical (esp. with high neuroticism). Impulsive:  Short attention span,  unconcerned with order, spontaneous.  Tends to lateness, often seen as irresponsible.  Often carefree and fun-loving (esp. with high extraversion).
Agreeable:  Friendly, warm.  Pleasant to others, avoids argument, enjoys social calm.  May be somewhat conformist or at least compromising. Disagreeable:  Hard to get along with.  Strong opinions, quite independent, enjoys argument.  Not concerned with keeping to social pleasantries.
Open:  Open to new experiences.  Enjoys cultural variety, the arts, philosophy, and so on.  Enjoys meeting people significantly different from themselves.
Conventional:  Prefers familiarity.  Likes things to stay the same.  Uncomfortable with people that are different.  Not interested in philosophy or high culture.
Active:  Enjoys activity, movement.  Can’t sit still for long.  Always looking for something to do.  Often enjoys engaging in sports, for example, or making things with their hands. Lethargic:  Inactive, slow.  Prefers sedate activities.  Prefers a walk or even sitting to vigorous activity.  Often perceived as being lazy.
Intelligent:  Able to absorb new information easily.  Understands even complex issues easily.  Solves problems easily. Unintelligent:  Finds learning difficult.  Must work hard to understand new things.  Gives up solving problems.
Feminine:  Nurturant, social, verbal, emotionally expressive.
Masculine:  Aggressive, less emotional attachment, more risk-taking.
Grounded:  Able to easily differentiate imagination from reality.  In touch with reality.  Free of hallucinations and delusions.
Psychoticistic:  Has difficulty distinguishing imagination from reality.  Prone to hallucinations and delusions.
Engaged:  Has an intuitive grasp of social interaction.  Able to detect subtle social cues.  Good at communicating feelings.
Autistic:  Does not appear to possess social instincts or learn subtle social cues.  Has difficulty with language and other forms of communication.  Highly literal.
Empathetic:  Understands and even shares in the feelings of others.  Capable of identifying with others.  Compassionate.
Psychopathic:  Does not identify with the feelings of others.  Feels little guilt or shame.  May even enjoy manipulating others or causing others pain or humilitation.