Psychology

EVIDENCE FOR BILOGICAL BASES OF PERSONALITY

For centuries humans tried to understand the relation between body and mind, between constitution and personality.
Personality is extremly complex . There will never be one single approach in terms of reductionist explanation, that will cover the whole concept. Therefore psychological phenomena have allways been approached from several perspectives, eg. the behavioral perspectives, the cognitive perspective, the biological perspective, and the interactional perspective. Each of these approaches to individuality offers a somewhat different explanation of why individuals act as they do, and in doing so, each approach makes a contribution to an integrated conception of the total person. This multiple approach to the phenomena of individuality and personality has its advantage. There is an proverb: “ let 1000 flowers flower, because this will always bring up something good and useful in the end”.

An still actual major issue in the domain is the genes versusus the enviroment debate ( Eaves and Young, 1981; Plomin, Defries and McClearn, 1990). Are we biological or a social creature? Or are we both? This debate is a consequence of a much older debate, a very influential controversy known as the ‘nature-nurture debate’. This longstanding discusssion is about the relative importance of biologiical and social factors in the development of individual differences. For a long time biological and social explanations seemed to be mutually exclusive, and always one approach seemed to be overriding the other, dependent on the zeitgeist. Here we will try an  psychobiological approach to personality.

For centuries humans tried to understand the relation between body and mind, between constitution and personality. Greek physicians in the fifth century B.C. proposed biochemical bases (humors) for normal and disordered personalities. In the first part of the 20th century, the psychodynamic perspective emerged from the work of Freud and his disciples. Freud, the neurologist and “biologist of the mind” (Sulloway,1979) regarded his psychological theories as an expedient strategy pending the development of a mature neuroscince (Freud,1920/1955).

In the second half of the century, the discovery of the effective drugs for treatments of anxiety, mood, and schizophrenic disorders resulted in a new science: psychopharmacology. Reasearch on the neurochemical basis of brain functions and then delineation of neurochemical patways mediated by specific neurotransmitters enlarged our understanding of the chemistry of brain function and its relation to cognition, emotion, and behavior.     

The last decade of the century has been called the Decade of Brain”. Have the insights gained  we will get others explanations about the relation beetween brain functioning and personality. Today everybody are agree that the Greek physicians had the right ideea but the wrong humors. Given the advances in the brain sciences in the last quarter of the century, Freud would probably have agreed that it is time to have another look at the psychobiology of personality ( Zuckerman, 1991).

Traits models

Traditionally the essence ogf the trait approach has been the assumtion that behaviour is primarily determined by stable generalized traits – broad dispostions to behave in  particular ways. Guided by this assumption, many investigators have searched vigorosly for these traits. Perhaps the chief goal of trait psychology has to find the person’s position on one or more trait dimensions ( for eaxmple, inteligence, introversion, anxiety etc) by comparing the individual with pthers under similar uniform conditions. Most of the psychologists consider that these dimensions tend to be stable across the situations and over time, theier focus in the study of individuality becomes the search to identify the person’s basic traits. The last decades witnessed a narrowing of the range of what are considered the basic dimnesions of personality from 16 or so to five or three. In fact the number of factors is not so important because broad factors incorporate narrower factors in a hierarchal order ( eysenck, 1967; Costa and McCrae,1985; Zuckerman et al., 1988), and a factoring of narrower factors usually reconstitues the broader factors so that how many factors depends on the level of analysis. Disagreements on what is a basic factor ofetn stem from differences in initial selection of variables. The importance of a factor in the analysis depends upon how many markers were chosen to represent the factor. If there is only one marker for a factor it is unlikely to emerge as an important one in the analysis. 

Aditionally, there is substantial agreement on two of these basic traits  ( extraversion, or socaibility, and neuroticism or anxiety) in nearly all taxonomic systems. Eysenck (1967,1991) has proposed three basic personality factors: extraversion (E), neurotiscism (N), and Psychoticism (P). Tellegen’s (!985) three-factor model includes positive afectivity (PA), negative affectivity (NA), and constraint as the basi factors. Tellegen has fond consistent corelation between his “big three” and Eysenck’s  three (E corrlates with PA, N with NA, and P with C). The “Big five” model merged from rating scales based on lexical analyses and was translated into a questionaire form by Costa and McCrae (1992). Thre big faive factors are extarversion, neuroticism, conscientiousness, agreeableness, and openness to experience (or intelect). 

Using factor analyses of personality scales (Zuckerman, Kuhlman, Thornquist, & Kiers,1991) and questionaires items (zuckerman, Kuhlman, Joireman, Teta, & Kraft,1993” Zuckerman,1994) have proposed an “alternative Five”: sociability, neuroticism-anxiety,impulsive sensation seeking, aggresion ostility, and activity. Zuckerman (1993) examinde the relation between Eysenck’s three, Costa and McCrae’s Big Five and Alternative Five. The results of corelations and factors analyses showed strong equivalence between extarversion (socaiability) and neuroticism measures in all systems and a strong negative relationship between agreeableness and aggresion-hostility in the two five factor models. Less strong relationships were found between P and Impulsive sensation seeking, and both of these were negatively related to conscintiousness.

Cloninger (1987) developed a biologically based three-factor system for personality including traits of novelty seeking, harm avoidance, and reward dependence. Later he expanded his system to seven factors, adding traits of cooperativeness, persistence, self-determination, andspirituality to the first three. Working together, Zuckerman and Cloninger, have examined the realationships between Eysenck’s three, Alternative five and Seven factor’s model. The results reveald interesting relations.

Harm avoidance was negatively related to extraversion (sociability) and positively related to neuroticism measures in the other two systems. Novelty seeking was primarily related to impulsive sensation seeking in the Alternative Five and equally to P and E In Eysenck’s system. Cooperativeness was negativellz related to aggression-hostility and persistence was related to activity in the Alternativre Five. Self-determination showed a weak negative relation to neuroticism in the other two systems. Reward dependence and  spiriruality showed few or only weak  relationship with other measures. The folowing table summarizes the relationships beetween personality variables in the five systems ( apud. Zuckerman, 1995).

 As we saw, enorms efforts have been made by personality psychologists to establish trait models and tie to specific  biological processes ( Cloninger, Svrakic, & Przybeck,1993: Zuckerman,1991, 1996 Depue.1996, Depue and Colins, 1999; Eysenck, 1990: Gray, 1997; Pickering & Gray, 1999; Tellegen, 1985;). Although similarities appear among almost all of these models, and clear relationship between theier basic dimensions,  they do not allways overlap in clear ways with one another. Therefore, rather than exploring a number of such models, here we will present just  “The Seven Factor Model” of human temperament and character (Cloninger, 1994). Before starting the presentation of Cloninger model is necessary to mention that many independent investigators, including Cloninger,  have evaluated the psychometric properties of quantitative tests for measuring personality and its disorders in the general popualtion as well as in clinical samples. This assessment produced evidence of the validity of two tests called the Tridimensional Personality Questionnaire (TPQ) ( Cloninger, 1987) and the more comprehensive Temperamnet and Character Inventory (TCI) ( Cloninger, et.al.1993) that was developed after the initial work on the TPQ. More recently, extensive work has been carried out by many investigators internationally to characterize the neuroanatomy, neuropsychology, neurochemistry and neurogenetics of human personality using TPQ and TCI. 

The Seven-Factor Model of  Personality

 Personality can be defined as the dynamic organization of the psychobiological systems that modulate adaptation to experience (Cloninger, 1987). A long tradition in psychology distinguishes two major domains of personality-temperament and character. According to early psychologists, temperament referred to our congenital emotional predisposition, whereas character was what people made of themselves intentionally (see Kant 1798/1974). To carry out psychobiological research, it useful to operationalize this distinction in-terms of individual differences in neuroadaptive processes. Accordingly, temperament can be defined as the automatic associative responses  to basic emotional stimuli that determine habits and skills, whereas character refers to the self-aware concepts that influence our voluntary intentions and attitudes (Cloninger et al. 1993).

Psychosocial researchers have usually defined temperament as those components of personality that are heritable, developmentally stable, emotion based, or uninfluenced by sociocultural learning (Goldsmith et al. 1987). Fortunately, these four alternative definitions are highly convergent; recent work shows that all dimensions of temperament, defined as individual differences in emotion-based habit patterns, are moderately heritable, stable from childhood through adulthood, and structurally consistent in different cultures and ethnic groups (Cloninger 1995). About 50% of the variance in temperament among individuals is heritable and stable from childhood through adulthood (see Table 3-1).

In contrast, character is weakly heritable but moderately influenced by sociocultural learing. It matures in a stepwise maner from infancy through late adulthood, and the timing and rate of transition between levels of maturity are nonlinear functions of antecedent temperament configurations and sociocultural education (Svrakic et al. 1996).

Table 3-1.         Difference in learning, brain systems, and etiology between temperament and character

Learning variable

Temperament

Character

Form of learning

   

Level of awareness

Automatic Intentional
Type of activity Habits, skills Goals, values

Learning principle

Associative Conceptual insight
conditioning
 
Brain systems Limbic system Neocortex
striatum
hippocampus
Etiologic components    

Genetic heritability

40%-60% 10%-15%

Shared sibling

environment

0 30%-35%
   

Random environment

40%-60% 40%-60%

 Temperament and Character

 The distinction between temperament and character appears to correspond to the dissociation of the major brain systems for procedural versus propositional memory and learning, as depicted in Figure 3-1 and documented in studies summarized in later tables and text. In other words, temperament involves individual differences in habit learning (i.e., procedural learning), whereas character involves differences in higher cognitive processing, such as concepts about self and relations to others. The distinction between these two major neural systems for adapta­tion to experience has had a variety of labels, such as percept versus concept, emotion versus volition, instinct versus will, and habit versus cognition. According to this psycho biological perspective, character development can be operationalized in terms of abstract symbolic processes that are most highly developed in humans, such as se1f-directed behavior, empathic social cooperation, and creative symbolic invention. The hipocampal formation and cerebral neocortex are essential for encoding such concept-based, symbolic representations of experience.

In contrast, temperament or basic emotionality can be operation­alized in terms of associative habit learning that is perceptually based and well developed at an early age in nearly all verte­brates, even those without differentiation of the cerebral neocor­tex (Cloninger 1994b, 1995). Recent work, described later, shows that psychophysiological markers of neocortical processing, such as the P300 evoked potential to target stimuli, are correlated with individual differences in character but not temperament. This dissociation underscores the neurobiological importance of the distinction between temperament and character, which is ne­glected by factor analytically derived models of personality.

The four dimensions of human temperament correspond closely to those observed in other mammals, such as rodents and dogs (Wilsson and Sundgren, 1997). Clinical descriptors of the four dimensions of human temperament and the three dimen­sions of character are summarized in Tables 3-2 and 3-3, re­spectively. In particular, the same multidimen­sional structure is observed in the general population (Cloninger et al. 1993) and in samples of psychiatric patients (Svrakic et al. 1993) or outpatients (Bayon et al. 1996).

The relationship of this multidimensional model to the clusters of DSM-IV (American Psychiatric Association, 1994) personality disorders is shown in Table 3-4. All clusters of per­sonality disorders are characterized by low scores in TCI self­directedness and cooperativeness. Deviations in temperament are associated with particular DSM-IV clusters: the anxious (C) cluster with high harm avoidance, the impulsive (B) cluster with high novelty seeking, and the aloof (A) cluster with low reward dependence. Furthermore, individual DSM-IV categories can be distinguished by a unique profile of TCI scores. For example, borderline personality disorder is characterized by an explosive temperament proffie (i.e., high harm avoidance, high novelty seeking, and low reward dependence) together with low char­acter scores. Such multidimensional decomposition allows a cli­nician to make mutually exclusive classifications without the usual problem of multiple overlapping diagnoses using ambig­uous DSM-IV checklists.

 

Table 3-2.         Temperament dimensions

Temperament

dimension

Descriptors of extreme variants
High

Low

Harm avoidance Pessimistic Optimistic
Fearful Daring
Shy Outgoing
Fatigable Energetic
     
Novelty seeking Exploratory Reserved
Impulsive Rigid
Extravagant Frugal
Irritable Stoic
     
Reward dependence Sentimental Critical
Open Aloof
Warm Detached
Sympathetic Independent
     
Persistence Industrious Lazy
Determined Spoiled
Ambitious Underachieving
Perfectionist Pragmatic

  

Table 3-3.         Descriptors of individuals who score high and low on the three character dimensions

Character

dimension

Descriptors of extreme variants
High Low
Self-directedness Responsible Blaming
Purposeful Aimless
Resourceful Inept
Self-accepting Vain
Disciplined Undisciplined
     
Cooperative Tender hearted Intolerant
Empathic Insensitive
Helpful Hostile
Compassionate Revengeful
Principled Opportunistic
     
Self-transcendent Self-forgetful Unimaginative
Transpersonal Controlling
Spiritual Materialistic
Enlightened Possessive
Idealistic Practical

 

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