To answer this question, we need to take a brief history lesson and to describe the work of Gordon Allport, Raymond Cattell, Hans Eysenck, Paul Costa & Robert McCrae. This is worthwhile because many of the tests and much of the terminology developed in the last century by these psychologists is still in widespread use today and forms the basis of current personality theory and consequently of personality tests.
Gordon Allport (1897–1967)
Allport was one of the first psychologists to focus on the study of the personality. He rejected both the psychoanalytic approach , which he thought often went too deep, and a behavioral approach, which he thought often did not go deep enough. He emphasized the uniqueness of each individual, and the importance of the present context, as opposed to past history, for understanding the personality. He identified thousands of personality traits and grouped these into three categories:
Cardinal Traits - a cardinal trait dominates the personality
across time and situations. A cardinal trait is the most important
component of your personality e.g. Ambition, Self-sacrifice, etc.
Very few people develop a cardinal trait and if they do, it tends
to be late in life.
Central Traits - five to ten traits that are stable across time and situations. These are the building blocks of personality. For example: friendliness, meanness, happiness, etc. Most personality theories focus on describing or explaining central traits.
Secondary Traits - these characteristics are only evident in some situations and are of less importance to personality theorists. They are aspects of the personality that aren’t quite so obvious or so consistent.
Allport was also one of the first researchers to draw a distinction between Motive and Drive. He suggested that a drive formed as a reaction to a motive may outgrow the motive as a reason. The drive then is autonomous and distinct from the motive. For example, the drive associated with making money to buy goods and services often becomes an end in itself.
Raymond Cattell (1905-1998)
Cattell took the thousands of traits described by Allport and condensed them down to 16 primary traits using the statistical method of factor analysis. The 16 PF (Personality Factors) test which resulted from this work is still in use today. He was an early proponent of using factor analytical methods instead of what he called "verbal theorizing" to explore the basic dimensions of personality, motivation, and cognitive abilities.
One of the most important results of Cattell's application of factor analysis was his discovery of 16 factors underlying human personality. He called these factors "source traits" because he believed they provide the underlying source for the surface behaviors we think of as personality. This theory of personality factors and the instrument used to measure them are known respectively as the 16 personality factor model and the 16PF Questionnaire.
Hans Eysenck (1916-1997)
Eysenck proposed that only two factors were necessary to explain individual differences in personality. He argued that Cattell's model contained too many factors which were similar to each other, and that a simple two factor model could encompass the 16 traits proposed by Cattell. This model had the following dimensions:
Eysenck argued that these traits were associated with innate biological differences. For example, extraverts need more stimulation than introverts do because they have lower resting levels of nervous system arousal than introverts. Eysenck developed a third factor, psychoticism, which dealt with a predisposition to be psychotic (not grounded in reality) or sociopathic (psychologically unattached).
The result was the so-called PEN personality model.
P scale: Psychoticism -------------------------------------- High Impulse Control
Aggressive, cold, egocentric, [Nonagressive, warm, concerned for others
impersonal, impulsive, antisocial, personally involved, considerate, social,
unemphathetic, creative, tough-minded empathetic, uncreative, persuadable]
E scale: Extraversion -------------------------------------- Introversion
Sociable, lively, active, assertive, [Hermetic, taciturn, passive, unassertive,
sensation-seeking, carefree, stoical, reserved, dependent,
dominant, surgent, venturesome even-tempered, risk-averse]
N scale: Neuroticism --------------------------------------- Emotional Stability
Anxious, depressed, guilt-feelings, unconcerned, happy, without regret,
low self-esteem, tense, irrational, high self-esteem, relaxed, rational,
shy, moody, emotional confident, content, controlled.
Paul Costa (1942-) & Robert McCrae (1949-)
In the final decades of the twentieth century an increasing number of psychologists came to the conclusion that the three factor model was too simple and that 16 factors were too many. In 1990 Paul Costa and Robert McCrae presented their ‘ Five Factor Theory’ and introduced the associated NEO Personality Inventory.
This Costa & McCrae model has received significant support from other research and is now widely accepted among psychologists. There is some minor disagreement regarding the exact definition and naming of these 5 factors but this is largely an academic debate. These 5 aspects of personality are referred to as the 5-factors or sometimes just ‘the Big 5’. Until now we have not really made any attempt to clearly define any of the personality traits. However, now that we have the 5 factor model we can proceed to look at these in detail.
You may also be interested in: Personality Tests Introduction, Why You Need to Understand Them, How They Work, How Many Personality Traits Are There?, The Big 5 Aspects of Personality, How Personality Profiles are Used, Your Personality at Work, Testing for Honesty, Integrity and Stress, Negative Aspects of Personality, Motivation, Extraversion and Leadership, Can You Beat the Personality Test, Understanding the Personality Test Industry, Even Popular Tests are Controversial and Best Practice Guidelines for Personality Tests.