16PF Questionnaire
The Sixteen Personality Factor Questionnaire (or 16PF), is a multiple-choice personality questionnaire which was scientifically developed over several decades of research by Raymond B. Cattell and his colleagues.  Beginning in the 1940s, Cattell used the new techniques of factor analysis (based on the correlation coefficient) in an attempt to try to scientifically discover and measure the fundamental traits of human personality (Cattell, 1946) .
In addition to the sixteen primary traits, these researchers also found five higher-level "second-order" traits of personality now known as the Big Five , which have become popularized in recent years.  From early in his research, Cattell found that the structure of personality was multi-level or hierarchical, with both primary and secondary level traits (Cattell, 1946, 1957) .  The sixteen primary factors were a result of factor-analyzing hundreds of ratings of everyday behaviors to find the structure behind them.  Then, five global (or second-order) factors were discovered by factor-analyzing the sixteen primary traits.  Thus, the 16PF test gives scores on both the second-order global traits which provide an overview of personality at a higher, conceptual level, as well as on the more precise primary traits, which give the fine details of each unique personality.  A listing of these traits can be found in the article on the 16 Personality Factor Model.  Cattell also found that there was a third-order level of personality organization that contained just two over-arching, top-level factors (Cattell, 1957) , but it seems that little time was spent on defining this most abstract level of personality organization.
Because of its scientific origins, there are decades of empirical research on the test, and it is part of Cattell's comprehensive theory of individual differences.  The test's 60 years of research have found it to be predictive in various settings, and to provide a more in-depth, integrated picture of the whole person than do many personality tests.  For example, it is commonly used in schools and colleges, clinical and counseling settings, in career counseling and employee selection and development, as well as in basic personality research.  Research has shown the test to predict a wide range of behaviors, such as creativity, academic achievement, cognitive style, empathy and interpersonal skills, leadership potential, conscientiousness, self-esteem, frustration tolerance, coping patterns, marital compatibility, and job performance  .  The test has also been translated into over 35 languages and dialects, and is widely used internationally.
Cattell and his co-workers also developed parallel personality questionnaires to measure traits in other age-ranges, such as the Adolescent Personality Questionnaire for ages 12 to 18 years.   A shorter version, the 16PF Select Questionnaire, was developed for personnel settings.  Cattell also developed non-verbal measures of ability, such as the three scales of the Culture-Fair Intelligence Test as well as tests of motivation.

# Basic Description of Test
The most recent edition of the Sixteen Personality Factor Questionnaire (16PF) is the fifth edition of the test.   The test was originally published in 1949; the second and third editions were published in 1956 and 1962, respectively; and the fourth edition had five alternative forms which were released between 1967 and 1969.  The fifth edition revision was focused on updating, improving, and simplifying the language used in the test; simplifying the answer format; developing new validity scales; improving the psychometric properties of the test, including new reliability and validity data; and developing a new standardization sample (of 10,000 people) to reflect the current U.S. Census population.
The 16PF Fifth Edition contains 185 multiple-choice items which are written at a fifth-grade reading level.  Of these items, 76% were from previous 16PF editions, although many were re-written somewhat to simplify or update the language. The item content sounds non-threatening and asks simple questions about daily behavior, interests, and opinions. One particular characteristic of the 16PF Questionnaire is that its items tend to sample a broad range of actual behavior by asking questions about daily, concrete situations, rather than asking the test taker to make self-ratings and self-assess their own personality as many tests do (e.g., "I am a warm and friendly person; I am not a worrier."). This type of simple, self-rating type question tends to reflect mainly the persons self-image, and thus is dependent on their level of self-awareness and their defensiveness about their actual traits.  Instead, most 16PF questions tend to ask about actual behavioral situations:
- When I find myself in a boring situation, I usually "tune out" and daydream about other things.    True/False.
- When a bit of tact and convincing is needed to get people moving, I'm usually the one who does it.   True/False.
The test provides scores on sixteen primary personality scales and five global personality scales, all of which are bi-polar, meaning that both ends of each scale have a distinct, meaningful definition.  The test also includes three validity scales: a bi-polar Impression Management (IM) scale, an Acquiescence (ACQ) scale, and an Infrequency (INF) scale.  The reasoning ability (Factor B) items appear at the end of the test booklet with separate instructions, since they are the only items that have right and wrong answers
Administration of the test takes about 35-50 minutes for the paper-and-pencil version and about 30 minutes by computer.  The test instructions are simple and straightforward, and the test is untimed, and thus it is generally self-administrable and can be used in either an individual or a group setting.  The 16PF test was designed for adults at least age 16 and older, but there are also parallel tests for various younger age ranges (e.g., the 16PF Adolescent Personality Questionnaire).
The 16PF Questionnaire has been translated into more than 35 languages and dialects.  Thus the test can be administered in different languages, scored based on a local, national normative sample, and reported in about 15 different languages.  The test has generally been culturally adapted in these countries, with local standardization samples plus reliability and validity information collected locally and presented in the manuals.
The test can be hand-scored using a set of scoring keys, or computer-scored by mailing in or faxing the answer sheet to the Publisher IPAT".  There is also a software system that can be used to administer and score the test, and an internet-based system, which also provides administration, scoring, and reports in different languages.  There are a number of computer-generated interpretive reports which can be used to help interpret the test for different purposes, for example, the Personal Career Development Profile, the Karson Clinical Report, The Couples Counseling Report, the Human Resource Development Report, the Teamwork Development Report, and the Leadership Coaching Report.  There are also many books that help with test interpretation, for example, 16PF Interpretation in Clinical Practice (Karson, Karson, & O'Dell, 1997), The 16PF: Personality in Depth (Cattell, H.B., 1989), or Essentials of the 16PF (Cattell, H.E. & Schuerger, J.M, 2003)
A shorter version of the test, the 16PF Select (Cattell, Cattell, Cattell & Kelly, 1999), was developed for use in time-sensitive, employee selection settings, and includes fewer items per scale than the regular test.  The 16PF Express (Gorsuch, 2007) is a very short, 15-minute, version of the test which has about four items per factor and a wider answer format (items have a four-point or five-point answer format), which is used mainly for research. The 16PF traits are also included in the PsychEval Personality Questionnaire (PEPQ), which combines measures of both normal and abnormal personality traits into one test (Cattell, Cattell, Cattell, Russell, & Bedwell, 2003)

# History and Development
The 16PF Questionnaire was created from a fairly unique perspective.  Most personality tests are developed to measure the preconceived traits that are of interest to the particular theorist or researcher.  The 16PF test was developed instead as part of a quest to first discover what the basic underlying traits of human personality were, and then to construct a test to measure these fundamental dimensions.
The main author of the test, Raymond B. Cattell, had a strong background in the physical sciences, especially chemistry, where the basic elements of the physical world were being discovered, placed in the periodic table, and used as the basis for future research.  From this background in the physical sciences, he developed the belief that all fields are best understood by first seeking to find the fundamental underlying elements, and then developing a valid way to measure and research these (Cattell, 1965) 
When Cattell moved into the field of psychology in the 1930s, he was disappointed to find that it consisted of a wide array of abstract, unrelated theories and concepts that had little or no scientific bases.  He found that most personality theories had their origins in philosophers such as Aristotle or Locke, or were developed by medical professionals, such as Jean Charcot or Sigmund Freud, who relied on intuition to reconstruct what they felt was going on inside people, based on observing individuals with serious psycho-pathological problems.  Cattell (1957)  described the concerns he felt as a scientist:
Thus, Cattells goal in creating the 16PF Questionnaire was to discover the number and nature of the fundamental traits of human personality and to develop a way to measure these dimensions.  At the University of London, Cattell worked with Charles Spearman who was developing the complex new method of factor analysis to aid in his quest to discover the basic factors of human ability.  Cattell developed the idea that factor analysis, a powerful new tool for discovering the basic underlying dimensions behind complex issues, could also be applied to the area of personality. He reasoned that human personality must have basic, underlying, universal dimensions just as the physical world had basic building blocks (like oxygen and hydrogen).  He felt that if the basic building blocks of personality were discovered and measured, then human behavior (e.g., creativity, leadership, altruism, or aggression) would become increasingly understandable and predictable.
Cattell and his colleagues began a comprehensive program of international research aimed at identifying and mapping out the basic underlying dimensions of personality. Their goal was to systematically measure the widest possible range of personality dimensions, in a belief that all aspects of human personality which are or have been of importance, interest, or utility have already become recorded in the substance of language (Cattell, R. B., 1943, p. 483). .  They wanted to include every known personality concept, and thus began with the largest existing compilation of personality traits (Allport and Odbert, 1936).  Over time, they used factor analysis to reduce the massive list of traits by analyzing the underlying patterns among them.  They measured different sources of personality information (peer ratings, daily measures of objective behavior, and questionnaire measures), and measured these traits in diverse populations, including working adults, university students, and military personnel. (Cattell, 1957, 1973). 
Over several decades of careful factor-analytic study, Cattell and his colleagues gradually refined and validated their list of underlying source traits.  The search resulted in the sixteen unitary traits of the 16PF Questionnaire.  These factors have remained basically the same over the last 50 years of research.  In addition, the 16PF Questionnaire traits are part of a multivariate personality model that provides a broader framework including developmental, environmental, and hereditary patterns of the traits and how they change across the life span (Cattell, 1973, 1979, 1980).  
The validity of the factor structure of the 16PF Questionnaire (the 16 primary factors and 5 global factors) has been supported by more than 60 published studies (Cattell & Krug, 1986; Conn & Rieke, 1994; Hofer and Eber, 2002).     Research has also supported the comprehensiveness of the 16PF traits: all dimensions on other major personality tests (e.g., the NEO Personality Inventory, the California Psychological Inventory, the Personality Research Form, and the Myers-Briggs Type Indicator) have been found to be contained within the 16PF scales in regression and factor-analytic studies (Conn & Rieke, 1994; Cattell, 1996).

# The Original Big Five Traits
From the beginning, Cattell found personality to have a multi-level, hierarchical structure.  The first goal of these researchers was to find the most fundamental primary traits of personality.  However, next they factor-analyzed these numerous primary traits to see if these traits had a structure of their own -- i.e. if some of them naturally went together in self-defining, meaningful groupings.
They consistently found that the primary traits came together in particular configurations to form a smaller number of secondary or global traits, each with its own focus and function within personality.  For example, the first global trait they found was Extraversion-Introversion.  It resulted from the natural affinity of five primary traits that defined different reasons for an individual to move toward versus away from other people (see below).  They found that there was a natural tendency for these traits to go together in the real world, and to define an important domain of human behavior -- social behavior.  This global factor Global Extraversion/Introversion (the tendency to move toward versus away from interaction with others) is composed from the following primary traits:
- Warmth (Factor A): the tendency to move toward others seeking closeness and connection because of genuine feelings of caring, sympathy, and concern (versus the tendency to be reserved and detached, and thus be independent and unemotional).
- Liveliness (Factor F) the tendency to be high-energy, fun-loving, and carefree, and to spontaneously move towards others in an animated, stimulating manner. Low-scorers tend to be more serious and self-restrained, and to be unrushed, forbearing, and judicious.
- Social Boldness (Factor H) the tendency to seek social interaction in a confident, fearless manner, enjoying challenges, risks, and being the center of attention. Low-scorers tend to be shy and timid with strangers, and to be more modest and risk-avoidant.
- Forthrightness (Factor N) the tendency to want to be known by othersto be open, forthright, and genuine in social situations, and thus to be self-revealing and unguarded.  Low-scorers tend to be more private and non-disclosing and to be harder to get to know.
- Affiliative (Factor Q2) the tendency to seek companionship and enjoy belonging to and functioning in a group (inclusive, cooperative, good follower, willing to compromise).  Low-scorers tend to be more individualistic and self-reliant and to value their autonomy.
In a similar manner, these researchers found that four other primary traits consistently merged to define another global factor which they called Receptivity or Openness (versus Tough-Mindedness).  This factor was made up of four primary traits that describe different kinds of openness to the world:
- Openness to feelings and artistic dimensions (Sensitivity  Factor I)
- Openness to abstract ideas and conceptual thinking (Abstractedness  Factor M)
- Openness to new approaches and innovation (Openness-to-Change  Factor Q1) and
- Openness to people (Warmth  Factor A).
Another global factor, Self-Controlled versus Unrestrained, resulted from the natural coming together of four primary factors that define the different ways that human beings control their behavior:
- Rule-Consciousness (Factor G) involves adopting and conscientiously following societys standards of behavior
- Perfectionism (Factor Q3) describes a tendency to be self-disciplined, organized, exacting, and goal-oriented
- Seriousness (Factor F) involves a tendency to be serious, cautious, and thoughtful in making decisions; and
- Groundedness (Factor M) involves a tendency to focus on concrete, pragmatic, realistic solutions.
Because the global factors were developed by factor-analyzing the primary traits, the meanings of the global traits are determined by the primary traits which make them up.  In addition, then the global factors provide the over-arching, conceptual framework for understanding the meaning and function of each of the primary traits.  Thus, the two levels of personality are essentially inter-connected and interrelated.
For example, two people might have the exact same level of Extraversion, lets say 70%, but be quite different from each other in their social behavior.  Because they are both at the 70%, they both tend to move toward others to about the same degree, but they may be doing it for different reasons. One person might achieve the 70% on Extraversion by being high on Social Boldness (Factor H: talkative, adventurous, attention-seeking) and on Liveliness (Factor F: high-energy, fun-loving, impulsive), but Reserved (low on Factor A: detached, unemotional, formal).  This individual would be bold, out-going, and talkative, but not very attentive to others feelings.  The other Extravert might be high on Warmth (Factor A: kind, soft-heated, and nurturing), and Group-Oriented (low on Factor Q2: companionable, cooperative, and participating), but Shy (low on Factor H: timid, modest, and easily embarrassed).  This individual would tend to be quite differentcaring, considerate, and attentive to others but not out-going or loud.
Today, the global traits of personality are commonly known as the Big Five.  The Big Five traits are most important in getting a theoretical understanding of the big, over-arching domains of personality and in understanding how different traits of personality relate to each other and how different research findings relate to each other.  They are also important for understanding individual personality results in getting a broad overview of the individuals personality make-up at the highest level of personality organization.  However, it is still the scores on the more specific primary traits that define the unique personality make-up of any individual.  These more-numerous primary traits have repeatedly been found to be the most powerful in predicting and understanding the complexity of actual daily behavior (Ashton, 1998; Goldberg, 1999; Mershon & Gorsuch, 1988; Paunonen & Ashton, 2001).