Personality psychology is a branch of psychology which studies personality and individual differences. One emphasis in this area is to construct a coherent picture of a person and his or her major psychological processes. Another emphasis views personality as the study of individual differences, in other words, how people differ from each other. A third area of emphasis examines human nature and how all people are similar to one other. These three viewpoints merge together in the study of personality.
Personality can be defined as a dynamic and organized set of characteristics possessed by a person that uniquely influences his or her cognitions, motivations, and behaviors in various situations (Ryckman, 2004). The word "personality" originates from the Greek persona, which means mask. Significantly, in the theatre of the ancient Latin-speaking world, the mask was not used as a plot device to disguise the identity of a character, but rather was a convention employed to represent or typify that character.
The pioneering American psychologist, Gordon Allport (1937) described two major ways to study personality, the nomothetic and the idiographic. Nomothetic psychology seeks general laws that can be applied to many different people, such as the principle of self-actualization, or the trait of extraversion. Idiographic psychology is an attempt to understand the unique aspects of a particular individual.
The study of personality has a rich and varied history in psychology, with an abundance of theoretical traditions. Some psychologists have taken a highly scientific approach, whereas others have focused their attention on theory development. There is also a substantial emphasis on the applied field of personality testing with people.
- 1 Philosophical assumptions
- 2 Personality theories
- 3 Personality tests
- 4 References
- 5 See also
- 6 External links
- 7 Further reading
Many of the ideas developed by the historical and modern Personality Theorists stem from basic philosophical assumptions they hold. A good textbook for understanding basic assumptions behind personality theories is Hjelle and Ziegler (1992) - this book is now out of print, but similar views are articulated by Ryckman (2000). Psychology is not a purely empirical discipline, as it brings in elements of art, science, and philosophy to draw general conclusions. The following five categories are some of the most fundamental philosophical assumptions where theorists disagree:
Freedom versus Determinism
The debate over whether we have control over our own behavior and understand the motives behind it (Freedom), or if our behavior is basically determined by some other force over which we might not have control (Determinism). We may merely respond to external forces like government, parents, professors, the economic system, etc; or we may even be constrained to behave in certain ways by our genetics, upbringing, etc. The causation may be probabilistic and therefore indeterminate.
Heredity versus Environment
Personality is thought to be determined largely by either genetics and heredity, or environment and experiences, or both. There is evidence for all possibilities.
Uniqueness versus Universality
The argument over whether we are all unique individuals (Uniqueness) or if humans are basically similar in their nature (Universality).
Proactive versus Reactive
Do we primarily act through our own initiative (Proactive), or do we react to outside stimuli (Reactive)?
Optimistic versus Pessimistic
Finally, whether or not we can alter our personalities (Optimistic) or if they remain the same throughout our whole lives (Pessimistic).
There are several theoretical perspectives on personality in psychology, which involve different ideas about the relationship between personality and other psychological constructs, as well as different theories about the way personality develops.
Critics of personality theory claim that personality is "plastic" across time, places, moods, and situations. Changes in personality may indeed result from diet (or lack thereof), medical effects, significant events, or learning. However, most personality theories emphasize stability over fluctuation.
According to the Diagnostic and Statistical Manual of the American Psychiatric Association, personality traits are "enduring patterns of perceiving, relating to, and thinking about the environment and oneself that are exhibited in a wide range of social and personal contexts." Theorists generally assume that a) traits are relatively stable over time, b) traits differ among individuals (e.g. some people are outgoing while others are shy), and c) traits influence behavior.
The most common models of traits incorporate three to five broad dimensions or factors. The least controversial dimension, observed as far back as the ancient Greeks, is simply extraversion vs. introversion (outgoing and physical-stimulation-oriented vs. quiet and physical-stimulation-averse).
- Gordon Allport delineated different kinds of traits, which he also called dispositions. Central traits are basic to an individual's personality, while secondary traits are more peripheral. Common traits are those recognized within a culture and thus may vary from culture to culture. Cardinal traits are those by which an individual may be strongly recognized.
- Raymond Cattell's research propagated a two-tiered personality structure with sixteen "primary factors" (16 Personality Factors) and five "secondary factors." A different model was proposed by Hans Eysenck, who believed that just three traits - extraversion, neuroticism and psychoticism - were sufficient to describe human personality. Differences between Cattell and Eysenck emerged due to preferences for different forms of factor analysis, with Cattell using oblique, Eysenck orthogonal, rotation to analyse the factors that emerged when personality questionnaires were subjected to statistical analysis. Today, the Big Five factors have the weight of a considerable amount of empirical research behind them. Building on the work of Cattell and others, Lewis Goldberg proposed a five-dimension personality model, nicknamed the "Big Five":
- Extraversion - outgoing and stimulation-oriented vs. quiet and stimulation-avoiding
- Neuroticism - emotionally reactive, prone to negative emotions vs. calm, imperturbable, optimistic
- Agreeableness - affable, friendly, conciliatory vs. aggressive, dominant, disagreeable
- Conscientiousness - dutiful, planful, and orderly vs. laidback, spontaneous, and unreliable
- Openness to experience - open to new ideas and change vs. traditional and oriented toward routine
For ease of remembrance, this can be written as either OCEAN or CANOE.
- John L. Holland's RIASEC vocational model, commonly referred to as the Holland Codes, stipulates that there are six personality traits that lead people to choose their career paths. This model is widely used in vocational counseling and is a circumplex model where the six types are represented as a hexagon where adjacent types are more closely related than those more distant.
Trait models have been criticized as being purely descriptive and offering little explanation of the underlying causes of personality. Eysenck's theory, however, does propose biological mechanisms as driving traits, and modern behavior genetics researchers have demonstrated a clear genetic substrate to them. Another potential weakness with trait theories is that they lead people to accept oversimplified classifications, or worse offer advice, based on a superficial analysis of one's personality. Finally, trait models often underestimate the effect of specific situations on people's behavior. It is important to remember that traits are statistical generalizations that do not always correspond to an individual's behavior.
Personality type refers to the psychological classification of different types of people. Personality types are distinguished from personality traits, which come in different levels or degrees. According to type theories, for example, there are two types of people, introverts and extraverts. According to trait theories, introversion and extraversion are part of a continuous dimension, with many people in the middle. The idea of psychological types originated in the theoretical work of Carl Jung.
Building on the writings and observations of Carl Jung, during WWII Isabel Briggs Myers and her mother Katharine C. Briggs delineated personality types by constructing the Myers-Briggs Type Indicator. This model was later used by David Keirsey with a different understanding from Jung, Briggs and Myers.
The model is an older and more theoretical approach to personality, accepting extraversion and introversion as basic psychological orientations in connection with two pairs of psychological functions:
Perceiving functions: intuition and sensing (trust in conceptual/abstract models of reality or concrete sensory-oriented facts)
Judging functions: thinking and feeling (thinking as the prime-mover in decision-making or feelings as the prime-mover in decision-making).
Briggs and Myers also added another personality dimension to their type indicator in order to indicate whether a person has a more dominant judging or perceiving function. Therefore they included questions designed to indicate whether someone desires to either perceive events or have things done so that judgements can be made.
This personality typology has some aspects of a trait theory: it explains people's behaviour in terms of opposite fixed characteristics. In these more traditional models, the intuition factor is considered the most basic, dividing people into "N" or "S" personality types. An "N" is further assumed to be guided by the thinking or objectication habit, or feelings, and be divided into "NT" (scientist, engineer) or "NF" (author, human-oriented leader) personality. An "S", by contrast, is assumed to be more guided by the perception axis, and thus divided into "SP" (performer, craftsman, artisan) and "SJ" (guardian, accountant, bureaucrat) personality. These four are considered basic, with the other two factors in each case (including always extraversion) less important. Critics of this traditional view have observed that the types are quite strongly stereotyped by professions, and thus may arise more from the need to categorize people for purposes of guiding their career choice. This among other objections led to the emergence of the five factor view, which is less concerned with behavior under work stress and more concerned with behavior in personal and emotional circumstances. Some critics have argued for more or fewer dimensions while others have proposed entirely different theories (often assuming different definitions of "personality").
Type A personality: During the 1950s, Meyer Friedman and his co-workers defined what they called Type A and Type B behavior patterns. They theorized that intense, hard-driving Type A personalities had a higher risk of coronary disease because they are "stress junkies." Type B people, on the other hand, tended to be relaxed, less competitive, and lower in risk. There was also a Type AB mixed profile. Dr. Redford Williams, cardiologist at Duke University, refuted Friedman’s theory that Type A personalities have a higher risk of coronary heart disease; however, current research indicates that only the hostility component of Type A may have health implications. Type A/B theory has been extensively criticized by psychologists because it tends to oversimplify the many dimensions of an individual's personality.
Psychoanalytic theories explain human behaviour in terms of the interaction of various components of personality. Sigmund Freud was the founder of this school. Freud drew on the physics of his day (thermodynamics) to coin the term psychodynamics. Based on the idea of converting heat into mechanical energy, he proposed that psychic energy could be converted into behavior. Freud's theory places central importance on dynamic, unconscious psychological conflicts.
Freud broke the human personality down to three significant components: the ego, superego, and id. The id is the source of sexual energy that builds up and needs to be released or expressed in some way. The id is motivated by the pleasure principle. The ego is the structure that helps the id express itself. It emerges in order to realistically meet the wishes and demands of the id in accordance with the outside world. It operates according to the reality principle. Finally, the superego exercises moral judgement and societal rules in keeping the ego and id in check. The superego is the last function of the personality to develop and may be seen as an outcome of the interactions with one's parents during the long period of childhood dependency. According to Freud, personality is based on the interaction of these three components.
Sexuality is a major component of Freud's theory. He believed that humans are sexual throughout childhood, though it is important to note that Freud's broad understanding of sexuality included all kinds of pleasurable feelings experienced by the human body. Freud proposed five psychosexual stages of personality development:
- Oral Stage - birth to approximately age one
- Anal Stage - two years of age
- Phallic Stage - between three and six
- Latency Period - about seven years old to puberty
- Genital Stage - occurs during adolescence
Freud believed that adult personality is determined by early childhood experiences. He suggested that events in the past could influence the present, such as when a person develops a fixation during one of these five stages and is unable to develop further.
One of Sigmund Freud's earlier associates, Alfred Adler, did agree with Freud that early childhood experiences are important to development, and believed that birth order may influence personality development. Adler believed the oldest was the one that set high goals to achieve to get attention back that they lost when the younger siblings were born. He believed the middle children were competitive and ambitious possibly so they are able to surpass the first-born’s achievements, but were not as much concerned about the glory. Also he believed that the last born would be more dependent and sociable but be the baby. He also believed that only children love being the center of attention and mature quickly, but in the end fail to become independent.
Heinz Kohut thought similarly to Freud’s idea of transference. He used narcissism as a model of how we develop our sense of self. Narcissism is the exaggerated sense of one self in which is believed to exist in order to protect one's low self esteem and sense of worthlessness. Kohut had a significant impact on the field by extending Freud's theory of narcissism and introducing what he called the 'self-object transferences' of mirroring and idealization. In other words, children need to idealize and emotionally "sink into" and identify with the idealized competence of admired figures such as parents or older siblings. They also need to have their self-worth mirrored by these people. These experiences allow them to thereby learn the self-soothing and other skills that are necessary for the development of a healthy sense of self.
Another important figure in the world of personality theory would be Karen Horney. She is credited with the development of the "real self" and the "ideal self". She believes that all people have these two views of their own self. The "real self" is how you really are with regards to personality, values, and morals; but the "ideal self" is a construct you apply to yourself to conform to social and personal norms and goals. Ideal self would be "I can be successful, I am CEO material"; and real self would be "I just work in the mail room, with not much chance of high promotion".
Margaret Mahler agreed with Klein's theory of linking relationships children have with their mothers to mental disorders of disturbed children. Certain disorders directly relate to what kind of relationship they had with their mothers. An example of this would be people diagnosed with schizophrenia. They are often too attached to their mother as children and even become obsessed, and never get over the "Oedipus" or "Electra" complex. Another example would be autistic children. Autistic children show no interest in their mother, relating to her, and so on. Both of these are very opposite reactions, but both have to do with the outcome of the mental disorder.
Freud used the term "object" to refer to any target that an infant uses to satisfy his or her needs. In Object Relations Theory the object is the aim of "relational needs" in human development. These objects are most often people, such as primary caretakers and significant others. However, in young children these objects may include a blanket, favorite toy, pacifiers, etc. The child becomes attached to the object because it provides pleasure for the child. When very young he is unable to distinguish himself from the object. For the child, the transitional object provides a connection between the child's inner and outer worlds. The child learns about separateness between subjective and objective. From birth through life, object relations theorists propose that individuals seek to develop human relationships and form attachments that may aid or hinder their development. (Engler, 2006).
Another theory related to Freud's psychodynamics is Transactional analysis.
Behaviorists explain personality in terms of the effects external stimuli have on behavior. It was a radical shift away from Freudian philosophy. This school of thought was developed by B. F. Skinner who put forth a model which emphasized the mutual interaction of the person or "the organism" with its environment. Skinner believed that children do bad things because the behavior obtains attention that serves as a reinforcer. For example: a child cries because the child's crying in the past has led to attention. These are the response, and consequences. The response is the child crying, and the attention that child gets is the reinforcing consequence. According to this theory, people's behavior is formed by processes such as operant conditioning. Skinner put forward a 'three term contingency model' which helped promote analysis of behavior based on the 'Stimulus - Response - Consequence Model' in which the critical question is: "Under which circumstances or antecedent "stimuli" does the organism engage in a particular behavior or "response," which in turn produces a particular "consequence"?"
Richard Herrnstein extended this theory by accounting for attitudes and traits. An attitude develops as the response strength (the tendency to respond) in the presences of a group of stimuli become stable. Rather than describing conditionable traits in non-behavioral language, response strength in a given situation accounts for the environmental portion. Herrstein also saw traits as having a large genetic or biological component as do most modern behaviorists.
Ivan Pavlov is another notable influence. He is well known for his classical conditions experiments involving a dog. These physiological studies on this dog led him to discover the foundation of behaviorism as well as classical conditioning. Pavlov would begin his experiment by first ringing a bell, which would cause no response from the dog. He would proceed to place food in front of the dog's face, causing the dog to salivate. Several seconds later, he would ring the bell again, causing the dog to now salivate. After continuing this experiment several times, the dog would salivate at just the ring of the bell. These conditioning experiments can be used for many different types of experiments.
John B. Watson, The Father of American Behaviorism, made four major assumptions about radical Behaviorisms -
- Evolutionary Continuity: The laws of behavior are applied equally to all living organisms, so we can study animals as simple models of complex human responses.
- Reductionism: All behaviors are linked to physiology.
- Determinism: Animals do not respond freely, they respond in a programmed way to external stimuli. Biological organisms respond to outside influences.
- Empiricism: Only our actions are observable evidence of our personality. Psychology should involve the study of observable (overt) behavior.
All behaviorists focus on observable behavior. Thus there is no emphasis on unconscious motives, internal traits, introspection, or self analysis. Behavior modification is a form of therapy that applies the principles of learning to achieve changes in behavior.
In cognitivism, behavior is explained as guided by cognitions (e.g. expectations) about the world, especially those about other people. Cognitive theories are theories of personality that emphasize cognitive processes such as thinking and judging.
Albert Bandura, a social learning theorist suggested that the forces of memory and emotions worked in conjunction with environmental influences. Bandura was known mostly for his "Bobo Doll experiment". During these experiments, Bandura video taped a college student kicking and verbally abusing a bobo doll. He then showed this video to a class of kindergartners who were getting ready to go out to play. When they entered the play room, they saw bobo dolls, and some hammers. The people observing these children at play saw a group of children beating the doll. He called this study and his findings observational learning, or modeling.
Early examples of approaches to cognitive style are listed by Baron (1982). These include Witkin's (1965) work on field dependency, Gardner's (1953) discovering people had consistent preference for the number of categories they used to categorise heterogeneous objects, and Block and Petersen's (1955) work on confidence in line discrimination judgments. More central to this field have been:
- Self-efficacy work, dealing with confidence people have in abilities to do tasks (Bandura, 1997);
- Locus of control theory (Lefcourt, 1966; Rotter, 1966) dealing with different beliefs people have about whether their worlds are controlled by themselves or external factors;
- Attributional style theory (Abramson, Seligman and Teasdale, 1978) dealing with different ways in which people explain events in their lives. This approach builds upon locus of control, but extends it by stating that we also need to consider whether people attribute to stable causes or variable causes, and to global causes or specific causes.
Various scales have been developed to assess both attributional style and locus of control. Locus of control scales include those used by Rotter and later by Duttweiler, the Nowicki and Strickland (1973) Locus of Control Scale for Children and various locus of control scales specifically in the health domain, most famously that of Kenneth Wallston and his colleagues, The Multidimensional Health Locus of Control Scale (Wallston et al, 1978). Attributional style has been assessed by the Attributional Style Questionnaire (Peterson et al., 1982), the Expanded Attributional Style Questionnaire (Peterson & Villanova, 1988), the Attributions Questionnaire (Gong-guy & Hammen, 1990), the Real Events Attributional Style Questionnaire (Norman & Antaki, 1988) and the Attributional Style Assessment Test (Anderson, 1988).
Walter Mischel (1999) has also defended a cognitive approach to personality. His work refers to "Cognitive Affective Units", and considers factors such as encoding of stimuli, affect, goal-setting and self-regulatory beliefs. The term "Cognitive Affective Units" shows how his approach considers affect as well as cognition.
Albert Ellis, an American cognitive-behavioral therapist, is considered by many to be the grandfather of cognitive-behavioral therapy. In 1955 Ellis developed Rational Emotive Behavior Therapy (REBT), which later came to be known as Rational Therapy (RT). REBT required that the therapist help the client understand — and act on the understanding — that his personal philosophy contains common irrational beliefs that lead to his own emotional pain. Because thinking and emotion have a cause and effect relationship, Ellis believes that the thoughts we have become our emotions and the emotions we have become our thoughts. The basic theory of REBT is that majority of people create their own sort of emotional consequences because to sustain an emotion it must have had some form of thought. Ellis also created the A-B-C theory of personality. (A), is the activating event which is followed by (B), the belief system that the person holds and then (C), the emotional consequence. What the theory states is that (A) does not cause (C); but that (B) causes (C). The emotional consequences are caused by what the person believes in. An example would be if a person is walking outside and a stranger in a car pulls up next to them asking for directions (A), and the persons' belief system is that any stranger in a car that wants directions wants to hurt you (B) so therefore the person fears the person in the car is going to hurt them (C).
Aaron Beck, who is widely noted as the father of cognitive-behavioral therapy (CBT), suggested that nearly all psychological dilemmas can be redirected in a positive (helpful) manner with the changing of the suffering individual's thought processes. He has worked extensively on depression and suicide, and is now redirecting his theories towards those with borderline personality disorder, and the various anxiety disorders (OCD, neurosis, phobias, PTSD, etc.). Extensive evidence has proven the effectiveness of combining CBT with pharmacotherapy in treating the most severe psychiatric disorders such as bi-polar disorder and schizophrenia. Aaron Beck's continuing research in the field has proven to be a greater success over time.
In humanistic psychology it is emphasized people have free will and that they play an active role in determining how they behave. Accordingly, humanistic psychology focuses on subjective experiences of persons as opposed to forced, definitive factors that determine behaviour. Abraham Maslow and Carl Rogers were proponents of this view, which is based on the "phenomenal field" theory of Combs and Snygg (1949).
Maslow spent much of his time studying what he called "self-actualizing persons", those who are "fulfilling themselves and doing the best that they are capable of doing". Maslow believes that all who are interested in growth move towards self-actualizing (growth, happiness, satisfaction) views. Many of these people demonstrate a trend in dimensions of their personalities. Characteristics of self-actualizers according to Maslow include the four key dimensions; 1) Awareness - maintaining constant enjoyment and awe of life.These individuals often experienced a "peak experience". He defined a peak experience as an "intensification of any experience to the degree that there is a loss or transcendence of self". A peak experience is one in which an individual perceives an expansion of his or herself, and detects a unity and meaningfulness in life. Intense concentration on an activity one is involved in, such as running a marathon, may invoke a peak experience. 2) Reality and problem centered - they have tendency to be concerned with "problems" in their surroundings. 3) Acceptance/Spontaneity - they accept their surroundings and what cannot be changed. And 4) Unhostile sense of humor/democratic - they do not like joking about others, which can be viewed as offensive. They have friends of all backgrounds and religions and hold very close friendships.
Maslow and Rogers emphasized a view of the person as an active, creative, experiencing human being who lives in the present and subjectively responds to current perceptions, relationships, and encounters. They disagree with the dark, pessimistic outlook of those in the Freudian psychoanalysis ranks, but rather view humanistic theories as positive and optimistic proposals which stress the tendency of the human personality toward growth and self-actualization. This progressing self will remain the center of its constantly changing world; a world that will help mold the self but not necessarily confine it. Rather, the self has opportunity for maturation based on its encounters with this world. This understanding attempts to reduce the acceptance of hopeless redundancy. Humanistic therapy typically relies on the client for information of the past and its effect on the present, therefore the client dictates the type of guidance the therapist may initiate. This allows for an individualized approach to therapy.Rogers found that patients differ in how they respond to other people. Rogers tried to model a particular approach to therapy- he stressed the response. These responses came in a variety of fashions:
A. Evaluative Response – Place a value judgment on person’s feelings B. Interpretive Response- tells the person what they’re really thinking or feeling. C. Reflective Response- Captures how someone is feeling right now about the situation.
Around the 1990s, neuroscience entered the domain of personality psychology. Whereas previous efforts for identifying personality differences relied upon simple, direct, human observation, neuroscience introduced powerful brain analysis tools like Electroencephalography (EEG), Positron Emission Tomography (PET), and Functional Magnetic Resonance Imaging (fMRI) to this study. One of the founders of this area of brain research is Richard Davidson of the University of Wisconsin-Madison. Davidson's research lab has focused on the role of the prefrontal cortex (PFC) and amygdala in manifesting human personality. In particular, this research has looked at hemispheric asymmetry of activity in these regions. Neuropsychological studies have illustrated how hemispheric asymmetry can affect an individual's personality (particularly in social settings) for individuals who have NLD (non-verbal learning disorder) which is marked by the impairment of nonverbal information controlled by the right hemisphere of the brain. Difficulties will arise in the areas of gross motor skills, inability to organize visual-spatial relations, or adapt to novel social situations. Frequently, a person with NLD is unable to interpret non-verbal cues, and therefore experiences difficulty interacting with peers in socially normative ways.
There are two major types of personality tests. Projective tests assume that personality is primarily unconscious and assess an individual by how he or she responds to an ambiguous stimulus, like an ink blot. The idea is that unconscious needs will come out in the person's response, e.g. a very hostile person may see images of destruction. Objective tests assume that personality is consciously accessible and measure it by self-report questionnaires. Research on psychological assessment has generally found that objective tests are more valid and reliable than projective tests.
Examples of personality tests include:
- Holland Codes
- Rorschach test
- Minnesota Multiphasic Personality Inventory
- Morrisby Profile
- Myers-Briggs Type Indicator
- Enneagram Type Indicator
- NEO PI-R
- Thematic Apperception Test
- Kelly's Repertory Grid
Critics have pointed to the Forer effect to suggest that some of these appear to be more accurate and discriminating than they really are.
- Abramson, L. , Seligman, M.E.P. & Teasdale,J. (1978). Learned helplessness in humans: Critique and reformulation. Journal of Abnormal Psychology, 87, 49-74.
- Allport, G. W. (1937). Personality: A psychological interpretation. New York: Holt, Rinehart & Winston.
- Baron, J. (1982). Intelligence and Personality. In R. Sternberg (Ed.). Handbook of Intelligence. Cambridge: Cambridge University Press.
- Bradberry, T. (2007). "The Personality Code." New York: Putnam.
- Engler, Barbara (2006). Personality Theories. Houghton Mifflin.
- Hjelle, L. & Ziegler, D. (1992). Personality: Basic Assumptions, Research and Applications.
New York: McGraw Hill
- Ryckman, R. (2004). Theories of Personality. Belmont, CA: Thomson/Wadsworth.
- Big Five personality traits
- Career development
- Clinical psychology
- Dissociative identity disorder
- Educational psychology
- Holland Codes
- Individual differences
- Myers-Briggs Type Indicator
- Personality disorder
- Trait theory
- Type A personality
- Will (philosophy)
- Freeview Video 'Predicting Personality' by the Vega Science Trust and the BBC/OU
- Personality Theories
- A contemporary approach to the field of personality psychology
- The personality project
- Personality: Theory & Perspectives - Individual Differences
- Thesis on the interpersonal theory of personality
- Snygg & Combs' phenomenal field psychology
- Karen Horney: Personality and gender
- Existential psychology
- Gordon Allport's personality definitions
- Buddhist psychology
- Holland's Types
- Holland Career Model
- Goldberg's International Personality Item Pool website
- Buss, D.M., & Greiling, H.(1999). Adaptive Individual Differences. Journal of Personality, 67, 209-243.
- Henry A. Murray and Clyde Kluckhohn, Personality in Nature, Society, and Culture (1953)
- Personalities and biopsychology
- Personality psychology at The Psychology Wiki
- Mischel, W. (1999). Introduction to Personality. Sixth edition. Fort Worth, Texas: Harcourt Brace.
- Bradberry, T. (2007). "The Personality Code". New York, New York: Putnam.
- Combs, Arthur W., and Snygg, Donald. : A New Frame of Reference for Psychology. New York, Harper and Brothers. Article on Snygg and Combs' Phenomenological Field Theory