Personality - The thoughts, feelings and behaviours that make an individual unique.
Temperament - The genetic component of personality.
Longitudinal study - A study carried out to show how behaviour changes over time.
Thomas, Birch and Chess (1977)
Aim: To discover whether ways of responding to the environment remain stable throughout life.
Method: They studied 133 children from infancy to early adulthood. The children’s behaviour was observed and their parents were interviewed. The parents were asked about the child’s routine and its reactions to change.
Results: The children fell into three types: ‘easy’, ‘difficult’ and ‘slow to warm up’. The ‘easy’ children were happy, flexible and regular. The ‘difficult’ children were demanding, inflexible and cried a lot. The children that were ‘slow to warm up’ did not respond well to change or new experiences to begin with, but once they had adapted they were usually happy.
Conclusion: These ways of responding to the environment stayed with the children as they developed. Thomas, Chess and Birch therefore concluded that temperament is innate.
Monozygotic Twins - Twins developed from one fertilised egg.
Dizygotic Twins - Twins developed separately fertilised eggs.
Buss and Plomin (1984)
Aim: To test the idea that temperament is innate.
Method: They studied 228 pairs of monozygotic twins and 172 pairs of dizygotic twins. They rated the temperament of the twins when they were 5 years old. They looked at three dimensions of behaviour: Emotionally, activity and sociability. They compared the scores for each pair of twins.
Results: There was a closer correlation between the scores of the monozygotic twins than between the scores of dizygotic twins.
Conclusion: Temperament has a genetic basis.
Kagan and Snidman (1991)
Aim: To investigate whether temperament is due to biological differences.
Method: Kagan and Snidman studied the reactions of four-month-old babies to new situations. For the first minute the baby was placed in a seat with the caregiver sitting nearby. For the next 3 minutes the caregiver moved out of the baby’s view while the baby was shown different toys by the researcher.
Results: 20% of the babies showed distress by crying, vigorous movement of the arms and legs and arching of the back. They were classed as high reactive. 40% of the babies showed little movement or emotion. They were classed as low reactive. The remaining infants fell somewhere between the 2.
In a follow- up study, 11 years later, Kagan and Snidman found there was still a difference in the way the two groups reacted to new situations; the high reactive were shy while the low reactive were calm.
Conclusion: Kagan and Snidman concluded that these 2 temperaments are due to inherited differences in the way the brain responds.
Type theory – personality types are thought to be inherited. They can be described using related traits.
Extroversion – a personality type to describe people who look to the outside world for entertainment.
Introversion – a personality type that describes people who are content with their own company.
Neuroticism – a personality type that describes people who are highly emotional and show intense reactions to fear.
Aim: To investigate personality differences between people.
Method: 700 servicemen completed a questionnaire. Eysenck analysed the results using factor analysis.
Results: He identified 2 dimensions of personality (extroversion, introversion and neuroticism- stability).
Personality scales – ways of measuring personality using yes/no questions.
Psychoticism – a third dimension identified by Eysenck. These people are hostile, insensitive and cruel.
APD – a condition in which the individual does not use socially acceptable behaviour/ consider the rights of others.
DSM-IV TR – lists different mental disorders and the criteria for diagnosing them
Amygdala – part of the brain involved in emotion.
Cerebral cortex (GM) – the outer layer of the brain.
Prefrontal cortex – the front of the brain involved in social and moral behaviour, controlling aggression.
Raine et al. (2000)
Aim: To support the theory that abnormalities in the prefrontal cortex cause APD.
Method: Magnetic resonance imaging (MRI) was used to study 21 men with APD and a control group of 34 healthy men. The subjects were all volunteers.
Results: The APD group had an 11% reduction in prefrontal grey matter compared with the control group.
Conclusion: APD is caused by a reduction in the brain’s grey matter.
Elander et al. (2000a)
Aim: To investigate the childhood risk factors that can be used to predict APD in adulthood.
Method: Researchers investigated 225 twins who were diagnosed with childhood disorders and interviewed those people 10-25 years later.
Results: Elander et al. found that childhood hyperactivity, conduct disorders, low IQ and reading problems were strong predictors of APD and criminality in adult life.
Conclusion: Disruptive behaviour in childhood can be used to predict APD in adulthood.
Aim: To investigate the development of offending and APD in males studied from childhood to the age of 50.
Method: The researchers carried out a longitudinal study of the development of APD in 411 males. They all lived in a deprived, inner-city area of London. They were first studied at the age of 8 and were followed up until the age of 50. Their parents and teachers were also interviewed. Searchers were carried out at a Criminal Records Office to discover if they or their family members had convicted of a crime.
Results: 41% of the males were convicted of at least one offence between the ages of 10-50. The most important risk factor for offending were criminal behaviour in the family, low school achievement, poverty and poor parenting.
Conclusion: Situational factors lead to the development of APD.