Personality Development And Temperament Research Paper

The personality types believed to be most prevalent in contemporary industrialized societies refer to usual styles of social interaction; degree of adherence to the ethical standards of the community; vulnerability to the emotions of anxiety, guilt, and anger; and receptivity to new ideas, beliefs, and attitudes. However, among individuals living in ancient agricultural societies, composed of small, stable geographically separate villages, variation in sociability would be less critical for adaptation than this trait is in the large cities of contemporary, industrialized nations.

The term temperament, on the other hand, refers to the profiles of mood, behavior, and physiology, believed to be under some genetic control, that appear relatively early in life and, together with experience, become the major personality traits of individuals in a particular society (Bates 1987). Temperamental qualities in children believed to be important at the start of the twenty-first century refer to ease of arousal to stimulation; the form and efficiency with which that arousal is regulated; activity level; irritability; form of reaction to unfamiliar people, objects, and situations; and capacity for sustained attention.

Scholars who believe that temperamental categories are applicable to adults have nominated avoidance of danger, seeking of novelty, dependence on social rewards, emotionality, activity, and sociability as primary temperamental characteristics (Buss and Plomin 1984).

1. Temperamental Contributions To Personality

The assumption that a young child’s temperament makes a contribution to the older individual’s personality has a long history. Hippocrates and Galen, two physicians living in ancient societies who were the founders of the temperamental theory, believed that the relative concentrations of four body humors— blood, phlegm, and yellow and black bile—created within each person a combination of the opposed dimensional qualities of warm versus cool and dry versus moist. The four temperamental types, called melancholic, sanguine, choleric, and phlegmatic, were the products of a particular combination of these two dimensions which were influenced, in part, by local climate and the person’s diet. Melancholics were high on the qualities of cool and dry because they possessed an excess of black bile and that is why they were tense, anxious, and depressed. Sanguine individuals were high on the warm and moist qualities because of an excess of blood and were outgoing and optimistic. The choleric was high on the qualities warm and dry because of an excess of yellow bile, and, as a result, was easily angered. The phlegmatic was high on the qualities of cool and moist because of an excess of phlegm and was low in energy and initiative. These concepts remained popular among Europeans and Americans until the end of the nineteenth century.

Interest in the contributions of temperament to personality receded during the first half of the twentieth century when political forces led to a rejection of the idea that biological processes contributed to personality. However, the contribution of temperament returned when the psychiatrists Alexander Thomas and Stella Chess (1977) nominated nine primary temperamental dimensions in children, along with three synthetic types that they called difficult child, easy child, and the child who is slow to warm up to unfamiliar situations. The difficult child, which was the least frequent category and comprised about 10 percent of the study group, was rather more likely than the other two to develop psychiatric symptoms in later childhood.

2. Reactivity To Stimulation In Infants

Ease of behavioral and physiological arousal to varied forms of stimulation, and the form of regulation of that arousal, are primary temperamental qualities in infants and young children (Rothbart 1989, Kagan 1994). Some infants become easily aroused by sight, sounds, and smells and thrash, cry, babble, or smile at these events. Other infants show minimal signs of arousal to the same stimulation. It is believed that about 20 percent of healthy, four-month-old infants react to varied forms of stimulation with frequent distress and vigorous motor activity. One-fourth of these infants, who are called high reactive, become very subdued, shy, fearful children in the second and third years and are more likely than others to develop anxious symptoms by school age. By contrast, about 40 percent of healthy infants show the opposite profile of a relaxed and minimally distressed reaction to stimulation. About one-fourth of these infants, who are called low reactive, become sociable, bold, and affectively spontaneous preschool children and minimally anxious seven year olds (Kagan 1994). A temperamental vulnerability to anxiety helps to explain why only a minority of children react to a particular stressful event with an anxious symptom, whether the traumatic event is an earthquake, kidnapping, divorce, or abuse. Only a fairly small proportion of children, usually less than 40 percent, react to the traumatic event with a fearful symptom or chronic anxiety.

Social experiences, especially experiences in the family and with peers, determine whether high reactive infants will develop a fearful personality and whether low reactive infants become bold extraverts. Hence, only about 15 percent of children who are extremely shy and anxious in the preschool years become introverted adolescents or adults (Caspi et al. 1988), and both the anxious-shy and the bold-sociable types are under modest genetic control.

There is disagreement as to whether temperament should be viewed as a continuous dimension or as a qualitative category. For example, some regard the tendency to approach or to withdraw from unfamiliar people and situations as a continuous dimension, while others believe that the child who usually approaches unfamiliar people and events and the child who usually avoids these events belong to separate, discrete categories. Because only about 15 percent of young children are consistently shy, avoidant, and timid in a large number of unfamiliar situations, while most children are subdued in only one type of situation, it is likely that the former child belongs to a qualitatively discrete group.

Most scientists believe that each of the many temperamental types possesses a unique set of inherited physiological features. Although most of these biological features are not yet discovered, it is known that fearful-avoidant children show greater cortical activation of the right frontal, compared with the left frontal, area as measured by absence of alpha activity in the EEG on the right side (Davidson 1994, Fox et al. 1994).

The brain contains over 150 different chemical substances, each of which influences the excitability of particular ensembles of neurons and brain circuits. It is assumed that children inherit different concentrations of these molecules, as well as different densities of the relevant receptors present on neuronal surfaces. As a result children are disposed to different mood and behavioral reactions. One example involves an enzyme called dopamine beta-hydroxylase. This enzyme, which is under genetic control, is required for the final step of the synthesis of norepinephrine. Children who have low levels of this enzyme will necessarily have less norepinephrine in their brain. Because brain norepinephrine renders a child vigilant and may increase the probability of a state of fear to novelty, children with low levels of the enzyme would be expected to be less fearful. Boys who are very aggressive or antisocial, often called conduct disorder, seem to be unafraid of punishment. These children have low levels of this enzyme (Rogeness et al. 1988). Dopamine, another essential brain neurotransmitter, affects motor behavior and cognitive processes mediated by the frontal cortex. Because the frontal cortex mediates planning and control of impulsivity, it is possible that children who inherit low levels of dopamine in the frontal area will be unusually impulsive. The rationale for administering the drug Ritalin to children who have been diagnosed as impulsive or hyperactive is that this drug increases the level of dopamine in the frontal cortex and, therefore, helps children control impulsive and potentially inappropriate behavior.

3. The Role Of Environment

Children are exposed to different environments over the course of childhood and these environments influence temperament in different ways. Therefore, there will be a large number of different personality profiles emerging from the combination of early inherited temperament and experience. Some of the important experiences include the socialization practices of the parents, the relationship to brothers and sisters, success or failure in school, and the quality of relationships with peers. The social class of the child’s family always exerts continuous influence on the personality that develops. A large birth cohort of children born on the island of Kauai followed from birth to the fourth decade of life revealed that the social class of the child’s family and early temperament were the two most important influences on the adult personality. Minimally irritable infants who were born to highly educated families were least likely to encounter school failure, display delinquent behavior, or to develop symptoms requiring referral to a physician or psychologist (Werner 1993).

3.1 Types Of Challenges

The most frequent personality profiles that develop in a particular culture are a function of the challenges to which the children in that culture must accommodate. Children in most settings deal with three classes of challenge: (a) unfamiliarity, especially unfamiliar people, tasks, and situations; (b) requests by legitimate authority for conformity to and acceptance of their standards, especially standards for competent task performance; and (c) domination by and/or attack from peers. In addition, all children must learn to control two families of emotions: anxiety, fear and guilt, on the one hand, and, on the other, anger, jealousy, and resentment.

4. Temperament And Moral Emotions

Variation in the intensity of the moral emotions of shame, guilt, and anxiety can be influenced by the child’s temperament and family experience. Shy, fearful children raised by mothers who used reasoning to socialize the child showed clearer signs of a strict conscience than most other children (Kochanska 1993). Sensory information from the body ascends in the spinal column and projects to the ventromedial surface of the prefrontal lobe. Children who experience consciously more intense bodily stimulation might be more vulnerable to the moral emotions than those who experience less stimulation. School-age boys who were low reactive infants and fearless children often have low sympathetic tone in the cardiovascular system. Boys who are members of this temperamental group growing up in homes with nurturant parents who socialize achievement and the control of aggression are likely to become popular group leaders. The same type of child raised by parents who did not socialize asocial behavior and who played with peers who committed asocial acts are at slightly higher risk for becoming delinquents (Caspi et al. 1995). It is believed that a small number of criminals who commit violent crimes ( probably fewer than 5 percent of all criminals) were born with a special temperament characterized by impulsivity and difficulty in controlling behavior.

5. Ethnicity And Temperament

Temperamental variation among ethnic groups is a delicate issue because of the ethnic strife that exists in many parts of the world. The average genetic distances for 100 different alleles monitoring physiological function measured in geographically separate populations were largest when Asians, Africans, and European-Caucasians were compared with each other. It is likely that some of these alleles make a modest contribution to variation in temperamental qualities. Asian-American infants, compared with European Americans, are calmer, less labile, less vocal, and more easily consoled when distressed (Kagan et al. 1994). It is relevant that Asian-American adult patients with a psychiatric diagnosis require a lower dose of therapeutic drug than European-American patients (Lin et al. 1986).

6. Personal Control

The renewed interest in temperament has generated discussion over the degree of responsibility each person should have for his or her behavior. Western society has, in the past, been Puritan in its commitment to the belief that all individuals have sufficient will power to control their behavior in most situations. This view has been eroded since the 1950s as more citizens have become willing to excuse some asocial actions as due to temperamental factors that were not within the agent’s sphere of control. It is not obvious that this permissiveness is more adaptive for a society than the traditional assumption that one of the significant products of human evolution is the capacity to monitor one’s behavior.

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