Explore Your Personality Traits | Sahaja Online

Personality Strengths Guide

Personality Theories

Explore Your Personality Traits

Several dominant personality theories have emerged over the years, and as you might expect, there are areas of consensus, but also certainly areas of controversy. It’s probably fair to say that, in the field of personality psychology, there is still no true consensus around any one theory.

There are two general approaches to viewing personality traits: nomothetic or idiographic. Nomothetic personality theory views people as unique in their combination of traits, but attempts to apply general personality rules to everyone — in other words, we all have the same personality traits (e.g., extroversion or neuroticism), but they vary only in degree, along a continuum, from person to person and may be expressed differently by each individual. Idiographic theory, on the other hand, which focuses on understanding the unique aspects of a particular individual, holds that people have unique personality structures, thus some traits are more important than others in understanding the personality of any one person.

Many early personality theorists attempted to explain personality in terms of biology — physiology and genetics — while others studied the impact of socio-behavioral conditioning. And the humanistic psychologists argue that the traditional models don’t account for the humanistic and transpersonal dimensions of psychology, such as autonomy, freedom of choice, purpose, and life satisfaction. The humanists tend to focus on what’s right with us, rather than what’s wrong with us. They propose that people are innately good and that mental health problems result from deviations from this natural tendency. More recently, genetic researchers are working to pinpoint the effects of certain gene variants on personality traits. Considering the merits of each point of view can provide a more evolved perspective of personality.

Most personality models revolve around an “essential trait” approach, which attempts to distill our many possible traits into small clusters of essential traits or “supertraits.” How many personality traits do we really have? Three? Five? Twenty-one? Depends on which theory you subscribe to. The predominant theories generally revolve around two models often referred to as the Super Three (or Three-Factor model) and the Big Five (Five-Factor model).

Explore the models below for yourself to develop an understanding of your own personality traits.

Allport and the Big Five

Psychologist Gordon Allport, often referred to as the “father of personality theory,” saw personality traits as the building blocks of an individual’s overall personality, but believed that traits differed in importance to each person (Allport, 1937). He envisioned some traits as big building blocks, some medium-sized, and some small. The bigger the size of the trait block, the more influence that trait has on a person’s life. So, a cardinal trait is a single giant-size trait around which someone organizes his/her life. An activist, for example, might organize his life around social consciousness.

But not everyone has a cardinal trait. Most of us tend to have at least one central trait — a major characteristic (e.g., honesty, optimism or outspokenness). Many of us have more than one central trait and we all have many secondary traits. While a secondary trait is an enduring personality trait, it doesn’t explain general behavioral patterns. Examples of secondary traits include, for example, personal styles (being a natty dresser) and preferences (preferring brown-eyed brunettes over blue-eyed blondes).

Allport developed a personality assessment by first distilling all 18,000+ personality-related adjectives in the dictionary into 200 clusters of synonyms (e.g., easygoing, lighthearted, carefree), and then forming trait dimensions with polar ends; for example, “responsible” at one pole, “irresponsible” at the other. In our daily lives, most of us land somewhere along the continuum between the two poles of a particular personality trait.

Allport was astonished to find that there were only five basic characteristics underlying all the adjectives that we use to describe ourselves — five categories sorting all our traits and behaviors — which became known as the “Big Five” dimensions of human personality. (Referred to by the acronym OCEAN.)

  1. Openness to experiences (inventive/curious vs. consistent/cautious). Appreciation for art, adventure, unusual ideas, and variety of experience. Openness reflects the degree of self-awareness, intellectual curiosity, creativity, imagination, independence and preference for new ideas, novelty and variety (vs. strict routine). At one end are individuals who are curious, creative, intellectual, and open-minded, contrasted with people who are shallow, simple, and generally less intelligent.
  2. Conscientiousness (efficient/organized easy-going/careless). Tendency to be organized and dependable, show self-discipline, act dutifully, aim for achievement, and prefer planned rather than spontaneous behavior. Organized, responsible, and cautious people are contrasted with those who are irresponsible, careless, and frivolous.
  3. Extroversion (outgoing/energetic vs. solitary/reserved). Energy, positive emotions, surgency/high level of engagement, assertiveness, sociability and the tendency to seek stimulation in the company of others, and talkativeness. Assertive, outgoing, and energetic people are contrasted with those who are quiet, reserved, and shy.
  4. Agreeableness (friendly/compassionate vs. analytical/detached). Tendency to be compassionate and cooperative and have a trusting and helpful nature, rather than suspicious, antagonistic or ill-tempered. Sympathetic, kind, and affectionate people are contrasted with those who are cold, argumentative, and cruel.
  5. Neuroticism (sensitive/nervous vs. secure/confident. Enduring tendency to experience negative emotions easily, including anger, anxiety, depression, and vulnerability. Also represents the degree of emotional stability and impulse control. Anxious, unstable, and moody personalities are contrasted with those who are emotionally stable, calm, and content.

While modern personality theorists have expanded and adapted Allport’s seminal work, it’s worth pointing out that his original five-factor model is never actually refuted; rather, it is, in fact, still the basis for — or has been centrally integrated into — today’s predominant personality models. Not everyone agrees, however, as to which five supertraits form the core of human personality.

Cattell’s 16 Personality Factors

Psychologist Raymond B. Cattell, like Gordon Allport, viewed language is a key source of information about personality and attempted to develop a “periodic table” of personality traits. Through analysis of both observer and behavioral data, Cattell  narrowed Allport’s lexicon of 18,000+ words down to just 4500 and filtered those to 171 trait names, which ultimately resulted in 16 personality dimensions (known as the 16 PF)…

  • Warmth: impersonal, distant, cool, reserved, detached, formal, aloof versus warm, outgoing, attentive to others, kindly, easy-going, participating, likes people
  • Reasoning: concrete thinking, lower general mental capacity, less intelligent, unable to handle abstract problems versus abstract-thinking, more intelligent, bright, higher general mental capacity, fast learner.
  • Emotional Stability: emotionally reactive, changeable, affected by feelings, less emotionally stable, easily upset versus emotionally stable, adaptive, mature, faces reality calmly
  • Dominance: deferential, cooperative, avoids conflict, submissive, humble, obedient, easily led, docile, accommodating versus dominant, forceful, assertive, aggressive, competitive, stubborn, bossy
  • Liveliness: serious, restrained, prudent, taciturn, introspective, silent versus lively, animated, spontaneous, enthusiastic, happy go lucky, cheerful, expressive, impulsive.
  • Rule-Consciousness: expedient, nonconforming, disregards rules, self-indulgent versus rule-conscious, dutiful, conscientious, conforming, moralistic, staid, rule bound
  • Social Boldness: shy, threat-sensitive, timid, hesitant, intimidated versus socially bold, venturesome, thick skinned, uninhibited
  • Sensitivity: utilitarian, objective, unsentimental, tough minded, self-reliant, no nonsense, rough versus sensitive, aesthetic, sentimental, tender-minded, intuitive, refined
  • Vigilance: trusting, unsuspecting, accepting, unconditional, easy versus vigilant, suspicious, skeptical, distrustful, oppositional
  • Abstractedness: grounded, practical, prosaic, solution oriented, steady, conventional versus abstract, imaginative, absent minded, impractical, absorbed in ideas
  • Privateness: forthright, genuine, artless, open, guileless, naive, unpretentious,                involved versus private, discreet, non-disclosing, shrewd, polished, worldly, astute, diplomatic
  • Apprehension: self-assured, unworried, complacent, secure, free of guilt, confident, self-satisfied versus apprehensive, self doubting, worried, guilt prone, insecure, worrying, self blaming
  • Openness to Change: traditional, attached to familiar, conservative, respecting traditional ideas versus open-to-change, experimental, liberal, analytical, critical, free thinking, flexibility
  • Self-Reliance: group-oriented,  affiliative, a joiner and follower dependent versus self-reliant, solitary, resourceful, individualistic, self-sufficient
  • Perfectionism: tolerates disorder, unexacting, flexible, undisciplined, lax, self-conflict, impulsive, careless of social rules, uncontrolled versus perfectionistic, organized, compulsive, self-disciplined, socially precise, exacting will power, control, self-sentimental
  • Tension: relaxed, placid, tranquil, torpid, patient, composed low drive versus tense, placid, tranquil, torpid, patient, composed, high energy, impatient, driven, frustrated, overwrought, time-driven

Eysenck’s Super 3 Personality Profiler

Professor Hans Eysenck of the University of London was a behaviorist whose personality theory was based primarily on physiology and genetics. While he believed in the influence of learned behaviors on psychological development, he viewed personality differences as being largely driven by heredity and focused his studies primarily on what we think of as temperament, or one’s “nature.”

Eysenck proposed 3 primary dimensions of personality or supertraits, within which 21 sub-traits should cluster consistently (known by the acronym PEN):

  1. Extroversion. Activity, liveliness, sociability/expressiveness, assertiveness, sensation-seeking/risk-taking/venturesome, aggressiveness, dominance, carefree/irresponsibility/lack of reflection
  2. Neuroticism. Anxiety, depression/unhappiness/moodiness, “emotional,” low self-esteem/inferiority/lack of autonomy, guilt, hypochondria, irrationality, obsessiveness, tenseness, shyness
  3. Psychoticism. Antisocial/coldness/impersonal/lack of empathy, aggressiveness, egocentricity, impulsivity, creativity, dogmatism, manipulativeness, tough-mindedness/practicality, ambition/achievement-oriented

Extroversion/Introversion

Eysenck believed that there’s an optimal level of cortical arousal at which we perform best. Extroverts, he believed, are chronically under-aroused and bored, thus are sensation-seeking — seeking additional external stimulation — to achieve optimal functionality. Introverts, on the other hand, are chronically over-aroused and nervous, thus seek peace and quiet to optimum functionality. In reality, at very low and very high levels of arousal, performance is low, while at a more optimal mid-level of arousal, performance is maximized.

Neuroticism

According to Eysenck, neuroticism is based on the activation threshold of the fight-or-flight response mechanisms within the sympathetic nervous system, all of which are actually measurable by such variables as heart rate, blood pressure, galvanic skin response and muscle tension. We can all be a bit neurotic from time to time, but people with chronically high neuroticism have low activation thresholds — it doesn’t take much to set them off. They tend to have difficulty controlling emotional reactions and experience negative affect such as excessive, irrational fear and anxiety and apprehensiveness and dread, even in the face of minor stressors. When fear and uncertainty rule their lives, anxious individuals may even develop avoidance behaviors to protect themselves from experiencing the anxiety, such as persistent, recurring thoughts and rituals (as in Obssessive-Compulsive Disorder, or phobic behaviors.

People with lower neuroticism are more emotionally stable. They have higher activation thresholds, greater emotional self-regulation abilities and are more likely to only experience anxiety in the face of imminent major stressors, rather than worrying about future events that may never even happen.

Psychoticism

Eysenck believed that psychoticism was associated not only with the tendency to experience psychosis (thought disorder in which there is a break with consensus reality), but also heavily associated with aggressive behaviors. He proposed that a higher level of testosterone was the physiological basis of psychoticism. He believed that psychotic behavior was rooted in such characteristics as tough-mindedness, egocentricity, non-conformity, impulsiveness, and that at the most extreme pole of high psychoticism one would find psychopathy — antisocial personalities such as sociopaths and psychopaths. But Eysenck’s view of the psychoticism dimension is controversial today. Many modern clinicians and researchers disagree that psychosis has any association with psychopathy (Krupp et al, 2013).

On Eysenck’s continuum, a person with high extroversion is sociable, popular, optimistic, carefree and rather unreliable, whereas a person with low extroversion is calm, quiet, reserved, even-tempered, introspective, and reliable. A person with high neuroticism is anxious, worried, moody, rigid, and unstable, whereas a person with low neuroticism is calm, even-tempered, carefree, and emotionally stable. A person with high psychoticism is troublesome, uncooperative, hostile, and socially withdrawn, whereas a person with low psychoticism is altruistic, socialized, empathic, and conventional (Eysenck, 1985).

While fewer modern personality theories revolve around Eysenck’s Three-Factor Model than Allport’s Five-Factor Model, Eysenck’s model remains important in the field of personality psychology because he was one of the first to demonstrate key relationships between biology and personality.

Zuckerman’s Alternate Five

Psychologist Marvin Zuckerman and colleagues developed a five-factor personality structure based on the assumption that “basic” personality traits are those with a strong biological-evolutionary basis. Their Alternate Five-Factor model bears a strong correlation to Allport’s Big Five, but with a twist: It excludes any equivalent to the dimension of openness to experience.

Traits are evaluated in terms of degree to which an individual experiences the following:

  1. Neuroticism-Anxiety. Anxiety, fear, general emotionality, psychasthenia (now termed obsessive-compulsive disorder), and inhibition of aggression. Also associated with obsessive indecisiveness, lack of self-confidence, and sensitivity to criticism.
  2. Aggression-Hostility. Hostility vs. social desirability. Aggression, hostility, anger, lack of regulatory control, and low social desirability. Associated with rudeness, thoughtlessness, vengefulness, quick temper and impatience, and antisocial behavior.
  3. Impulsive Sensation-Seeking. Low socialization, and high psychoticism, impulsivity, and sensation-seeking. Impulsivity includes a lack of “planfulness” and a tendency to act without thinking. Sensation-seeking includes a desire for shrills, excitement, novelty, variety, and unpredictable situations and relationships.
  4. Extroversion-Sociability. Seeks affiliation, social participation, interactions with many people, “life of the party,” dislike of isolation.
  5. Activity. Energetic behavior and persistence; associated with a need to stay active and feelings of restlessness.

You’ll notice that several dimensions of the Alternative Five model generally correspond to traits in Eysenck’s three-factor model, and to four of the five traits in Allport’s model, even though the labels and clusterings are slightly different. Zuckerman also believed that Activity should be an independent dimension of temperament, distinct from Sociability; however, most subsequent reanalyses by other researchers have found that Activity, Sociability and Extroversion all load into a single factor.

But why was openness to experience excluded? Zuckerman argues that Allport’s openness to experience does not meet the criteria for a “basic” factor (or supertrait) of personality. He believed that basic factors should have biological markers, moderate heritability and — most critically — a biological-evolutionary basis that can be identified in non-human species. He claims that markers such as culture, intellect, and openness should be excluded because these traits are not present in non-human species and that 5 of the 6 the facets of openness don’t involve activity, behavior or actions (e.g., fantasy, aesthetics, feelings, ideas, values). But try telling that to the chimpanzees…

A few studies have used tools such as MRI and the Chimpanzee Personality Questionnaire (yes, there really is such a thing!) to analyze extroversion, conscientiousness, agreeableness, openness and dominance across hundreds of apes in captivity. One review found that extroversion, neuroticism, and agreeableness were found most consistently across different species of apes, followed by openness (Weiss et al, 2007). Only chimpanzees showed dimensions of conscientious behavior.

Other researchers disagree with Zuckerman and colleagues’ exclusion of openness to experience, as well…

McCrae & Costa’s 5-Factor NEO

Zuckerman’s omission of the openness to experience dimension has been criticized by researchers Robert McCrae and Paul Costa (1992), who reanalyzed Zuckerman’s data and developed their own five-factor model. Costa and McCrae argued that Zuckerman’s “cognitive structure” (dislike of ambiguity or uncertainty in information) factor is, in fact, a valid marker of (low) openness (McCrae, & Costa, 2003).

The alternate 5-factor model proposed by Robert McCrae and Paul Costa (1992) includes these Big 5 supertraits (Acronym NEOAC, NEO) with polar opposites in parentheses:

  1. Neuroticism (Emotional Stability)
  2. Extroversion (Introversion)
  3. Openness to experience (Closed to experiences)
  4. Agreeableness (Disagreeableness)
  5. Conscientiousness (Lack of conscientiousness)

 

Each of the 5 McCrae’s & Costa’s supertraits is measured by 6 facets or subordinate traits:

N E O A C
Anxiety Warmth Fantasy Trust Competence
Angry hostility Gregariousness Aesthetics Straightforward-ness Order
Depression Assertiveness Feelings Altruism Dutifulness
Self-consciousness Activity Actions Compliance Achievement striving
Impulsiveness Excitement-seeking Ideas Modesty Self Discipline
Vulnerability Positive emotion Values Tender-mindedness Deliberation

Cloninger’s Temperament & Character Inventory

Psychiatrist Robert Cloninger’s popular psychobiological 7-factor model of personality is an integrative model, adding humanistic and transpersonal touches to traditional Five-Factor personality theory. Several studies have concluded that Cloninger’s 7 dimensions are substantially covered by the 5-Factor models, such as Allport’s Big Five and McCrae & Costa’s Alternative Five (De Fruyt et al, 2000; Cloninger & Zuckerman, 1996).

Cloninger’s 7-Factor model identifies 4 dimensions of temperament and 3 dimensions of character:

TEMPERAMENT

  1. Novelty seeking
    • Exploratory excitability
    • Impulsiveness
    • Extravagances
    • Disorderliness
  2. Harm avoidance
    • Anticipatory worry
    • Fear of uncertainty
    • Shyness
    • Fatigability
  3. Reward dependence
    • Sentimentality
    • Openness to warm communication
    • Attachment
    • Dependence
  4. Persistence
    • Eagerness of effort
    • Work hardened
    • Ambitious
    • Perfectionist
  5. CHARACTER Self-directedness
    • Responsibility
    • Purposeful
    • Resourcefulness
    • Self-acceptance
    • Enlightened second nature
  6. Cooperativeness
    • Social acceptance
    • Empathy
    • Helpfulness
    • Compassion
    • Pure-hearted conscience
  7. Self-transcendence
    • Self-forgetful
    • Transpersonal identification
    • Spiritual acceptance

You’ll note that Cloninger’s model differs from Zuckerman’s and Eysenck’s models in that their models do not recognize openness to experience. And most importantly, only Cloninger’s 7-factor model includes a transpersonal dimension (e.g., self-transcendence, maturity and self-actualization) and differentiates between character and temperament. Cloninger believed that Five-Factor models didn’t include domains of personality such as autonomy and moral values that were relevant to assessing personality disorders. His original research found that temperament alone did not capture the full range of human personality, thus he added the Character domain, using character traits to measure a person’s humanistic and transpersonal style; for example: self-directedness (reliable, purposeful vs. blaming, aimless); cooperativeness (tolerant, helpful vs. prejudiced, revengeful); and self-transcendence (self-forgetful, spiritual vs. self-conscious, materialistic). He believed that the Character dimension measured an individual’s capacity for mental self-government, as well as the presence and severity of personality disorder.

In presenting a perspective of personality, Cloninger often cites Immanuel Kant, who defines character as “what people make of themselves intentionally.” The Character facets have strong relationships with more recently evolved regions of the brain (such as the frontal, temporal, and parietal neocortex) that regulate the learning of facts and propositions. By contrast, the Temperament dimensions have strong relationships with the older cortico-striatal and limbic systems that regulate habits and skills, suggesting, perhaps, that the core temperament aspects of personality may be more deeply ingrained in us, while the facets of character give us an opportunity to adjust and improve our core traits for the better.

In his book, Feeling Good: The Science of Well-Being, Cloninger describes a desire to find a scientific basis for personality that goes beyond the level of description, saying:

“We have to see the whole person as more than a collection of disease states: a person is composed of multiple elements of body, mind, and spirit…. What has become increasingly clear to me is that man has a natural integrative tendency that leads to health, and that disease emerges whenever there is a block. Blocks can come from a genetic predisposition that interferes with natural development, from social learning, or from prior experiences that are unique to the individual.”

Cloninger has argued that the Temperament dimensions are associated with subjective well-being and, to some extent, with physical health. He believes that psychological well-being ultimately depends on the development of the facets within the three Character dimensions, such as autonomy and life purpose from self-directedness, positive relations with others through cooperativeness, and personal growth and self-actualization from self-transcendence. He suggests that separating biomedical, psychosocial, and spiritual approaches may actually interfere with the development of well-being.

How does Self-Transcendence influence personality? Self-Transcenders have a desire to reach for something higher than their individual existence, and with the actualization of that desire, they often become dedicated to, as psychologist Abraham Maslow put it, “causes outside their own skin.” According to Cloninger’s model, self-transcendence can manifest as an intuitive understanding of elevated aspects of humanity, like compassion, ethics, art, and culture. Others who experience it may also describe an awareness of a divine presence.

High Self-Transcenders report frequent experiences of “boundlessness” and “inseparability.” They lose awareness of their separateness when absorbed in what they love to do or when appreciating the wonders and mysteries of life. Cloninger has correlated such experiences of self-forgetfulness and transpersonal identification to what Freud called “oceanic feelings,” which is different from intellectual adherence to any particular religious dogmas or rituals. Cloninger, like other psychiatrists such as Carl Jung and Viktor Frankl, believed that self-transcendence is essential to the integration and maturation of personality. He also believed that people need to experience Self-Transcendence in order to cope well with suffering and to simply enjoy life’s wonders and mysteries fully. He found that people who score high on all three character traits (self-directedness, cooperativeness, and self-transcendence) had the highest level of well-being, as measured by presence of positive emotions, absence of negative emotions, satisfaction with life, and virtuous conduct.

Cloninger proposes that stimulating character development and self-awareness — whether through mental exercises or through a process such as meditation — fosters a healthy lifestyle with three sets of goals and values: 1) Working in the service of others, thereby increasing love and cooperativeness; 2) letting go of fighting and worrying, thereby increasing hope and self-directedness; and 3) growing in awareness, thereby increasing faith and Self-Transcendence. His model may be indicative of current thinking in the field of personality psychology.

It also bears mentioning that Cloninger’s model tends to resonate well with the personality goals of typical Sahaja practitioners and may, in fact, suggest an initial personality improvement blueprint for establishing a meditative practice.

References

Allport, G. W. (1937). Personality: A psychological interpretation. New York: Holt, Rinehart & Winston.

Cloninger, C.R.; Svrakic, DM; Przybeck, TR (December 1993). “A psychobiological model of temperament and character”. Archives of General Psychiatry 50 (12): 975–90.

Cloninger, C. Robert; Svrakic, Dragan M. Strack, Stephen (Ed); Lorr, Maurice (Ed), (1994). Differentiating normal and deviant personality by the seven-factor personality model. (pp. 40-64). New York, NY, US: Springer Publishing Co, xviii, 444 pp.

C. Robert Cloninger. (1994). The temperament and character inventory (TCI): A guide to its development and use. St. Louis, MO: Center for Psychobiology of Personality, Washington University.

C. Robert Cloninger, Rolf Adolfsson, and Nenad M. Svrakic. “Mapping genes for human personality.”  Nature Genetics, Vol. 12, January 1996.

Cloninger, CR; Zohar, AH (2011). “Personality and the perception of health and happiness”. Journal of affective disorders 128 (1–2): 24–32.

Costa, Paul T.; McCrae, Robert R. (1992). “Four ways five factors are basic”. Personality and Individual Differences 13 (6): 653. doi:10.1016/0191-8869(92)90236-I.

Costa, P.T.,Jr. & McCrae, R.R. (1992). Revised NEO Personality Inventory (NEO-PI-R) and NEO Five-Factor Inventory (NEO-FFI) manual. Odessa, FL: Psychological Assessment Resources.

Costa, P.T. Jr.; Terracciano, A.; McCrae, R.R. (2001). “Gender Differences in Personality Traits Across Cultures: Robust and Surprising Findings”. Journal of Personality and Social Psychology 81 (2): 322–331.

De Fruyt, F.; Van De Wiele, L. & Van Heeringen, C. (2000). “Cloninger’s Psychobiological Model of Temperament and Character and the Five-Factor Model of Personality”. Personality and Individual Differences 29 (3): 441–452.

Hans Jürgen Eysenck. (1967) The Biological Basis of Personality. Transaction Publishers.

Eysenck H. J. (1992). The definition and measurement of psychoticism. Pers. Indiv. Differ. 13, 757–785.

Eysenck H. J., Eysenck S. B. G. (1977). Psychoticism as a Dimension of Personality. Oxford: Crane and Russak.

Eysenck, H. J., & Eysenck, M. W. (1985). Personality and individual differences: A natural science approach. New York: Plenum.

Daniel Brian Krupp, Lindsay A. Sewall, Martin L. Lalumière, Craig Sheriff, and Grant T. Harris. Psychopathy, adaptation, and disorder. Frontiers in Psychology 2013; 4: 139.

McCrae, R. R., Costa, P. T. (2003). Personality in adulthood, a five-factor theory perspective (2nd ed.). New York: Guilford Press.

McCrae RR, Terracciano A, et al. Universal features of personality traits from the observer’s perspective: data from 50 cultures. J Pers Soc Psychol. 2005;88:547–561.

Zuckerman, Marvin (1992). “What is a basic factor and which factors are basic? Turtles all the way down”. Personality and Individual Differences 13 (6): 675.

Marvin Zuckerman and C. Robert Cloninger (August 1996). “Relationships between Cloninger’s, Zuckerman’s, and Eysenck’s dimensions of personality”. Personality and Individual Differences 21 (2): 283–285. doi:10.1016/0191-8869(96)00042-6.

Alexander Weiss, James E. King And William D. Hopkins. A Cross-Setting Study of Chimpanzee (Pan troglodytes) Personality Structure and Development. Am J Primatol. Nov 2007; 69(11): 1264–1277.