Personality disorders are thought to result from a difficult temperament (as well as biological and social factors). Personality traits and temperaments are dimensional characteristics that are heritable and manifest early in life. These characteristics underlie or influence cognitive processes, interpersonal and social functions, emotional and affective states and biological stress systems (Howland, 2007; Shiner, 2005).

Traditionally temperament is distinguished from personality because it refers to stable individual differences that appear from birth onwards. Personality on the other hand develops over time and is thought of as emerging later in life (Shiner, 2005; Mervielde, De Clercq, Fruyt & Leeuwen, 2005).

Temperament can be defined as a person’s innate or biologically shaped basic disposition to emotional response. Buss and Plomin distinguished four temperamental dimensions: emotionality, activity and sociability Emotionality involves intense activation of the sympathetic nervous system and hence high emotional arousal. The second temperamental dimension is measured by the rate and amplitude of speech and movement, displacement of body movements and duration of energetic behaviour.

Sociability refers to the preference for being with others, the need to share activities and receive rewarding attentions as a result of social interaction. Goldsmith and Campos define temperament as individual differences in the probability of experiencing and expressing primary emotions and arousal (Mervielde, De Clercq, Fruyt & Leeuwen, 2005).

Thomas and Chess (1977) conducted a study of 136 children whose development was closely monitored for a number of years. The authors identified nine categories of behaviour that they labelled temperament. The categories included activity level, rhythmicity (regularity), approach or withdrawal, adaptability, intensity of reaction, threshold of responsiveness (sensitivity to stimuli), quality of mood (disposition), distractibility, and attention span, and persistence.

That these aspects of temperament are observable shortly after birth and remain consistent throughout childhood indicates that they have some constitutional, if not genetic, basis. It has been suggested that it is the plasticity of the temperament that allows the environmental factors such as childrearing practices to have an equal or greater influence on development and our personality.

It is suggested that it is in the way the care giver responds to the child’s temperament that predisposes them to personality disorders. Negatively emotional or “difficult” infants and toddlers are more affected by rearing experience that those with easy temperament (Belsky & Pluess, 2009). Children with difficult temperament may result in their parents rejecting them or defaulting from providing adequate love that is critical in the early stages of development (Barlow & Durand, 2009).

This rejection may in turn result in social alienation and low self esteem in adulthood, thereby causing entrenched dysfunctional ways of thinking, feeling, behaving and relating. For example, nervous parents might be unhappy with a baby who has a very active temperament and try to restrain him or her at every opportunity. The child might then develop an avoidant personality disorder as a way of coping with constant frustration and parental disapproval.

Problems develop when the environment (or adults) put demands on the child which are not congruent with the child’s temperament. When a child fits with the demands of his or her environment, that child grows. When the child does not fit, problems in interaction with that environment occur predisposing that child to numerous personality disorders. Since children must learn to adapt to their specific care givers and families, they may develop personality disorders in the course of struggling to survive psychologically in disturbed or excessively stressful family environments (Barlow & Durand, 2009).

Social theories hold the position that personality disorders reflect learned responses, having much to do with reinforcement, modelling, and aversive stimuli as contributing factors. Psychoanalysts also agree that a traumatic childhood experiences such as abuse and neglect contributes towards the development of most personality disorders. According to psychodynamic theories, personality disorders reflect deficiencies in ego and superego development which are related to poor mother-child relationships characterised by unresponsiveness, overprotectiveness, or early separation.