Thomas, chess and birch
Aim: To discover whether ways of respoding to the envrionment remain stable throughout life.
Method: They studied 133 childre from infacy to early adulthood. The children's behaviour was observed and their parents were interviewed. The parents were asked about the childs routine and its reaction to change.
Results: they found that the children fell into three types of categories 'easy', 'difficult' and 'slow to warm up'. The 'easy' children were happy, flexible and regular. The 'difficult' children were demanding, inflexible and cired 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 temperment is innate/natural.
Buss and plomin
Aim: to test the idea that temperment is innate/natural.
Method: they studied 228 pairs of monozygotic twins (developed from one fertilised egg) and 172 pairs of dizygotic twins (developed from two seperate fertalised eggs). They rated the temperament of the twins when they were five years old. They looked at three dimensions of behaviour:
- Emotionally -how strong the child's emtotional repsonse was
- Activity -how energetic the child was
- Sociability -how mmuch the child wanted to be with other people
They then compared the scores for each pair of twins.
Results: there was a closer correlation between the scores of the monozygotic twins than between the dizygotic twins.
Conclusion: temperament has a genetic basis.
Kagan and snidman
Aim: to inestigate 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 wa splaced in a seat with the caregiver sitting nearby. For the next three minutes the caregiver moved out of the baby's view while the baby was shown different toys by the researcher.
Results: twenty per cent of the babies showed distress by crying, vigorous movement of the arms and legs and arching of the back. Forty per cent of the babies showed no emotion and little movement. They were classed as low reactive. The remaining infants fell somewhere inbetween.
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 reactives were shy while the low reactives were calm.
Conclusion: Kagan and snidman concluded that these two temperaments are due to inherited differences in the way the brain responds.
Theory of personality
Aim: to ivestigate personality differences between people.
Method: 700 servicemen were completed a questionnaire. Eysenck analysed the results using a statistical technique known as factor analysis.
Results:he identified two dimensions of personality: extroversion, introversion, stable and neuroticism.
Conclusion: everyone can be placed along these two dimensions of personality. Most people lie in the middle of the scale.
Biological causes of APD
Raine et al
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 11 per cent reuction in prefrontal grey matter compared with the control groups.
Conclusion: APD is caused by a reduction in the brain's grey matter.
Studies of the situational causes of APD
Aim: to investigate the development of offending and antisocial behaviour in males studied from childhood to the age of 50.
Method: the researchers carried out a longitudal study of the development of antisocial and offending behaviour in 411 males. They all lived in a deprived, inner-city area of London. They were first studied at the age of eight and were followed up until the age of 50. Their parents and teachers were also interviewed. Searches were carried out at the Criminal Records Office to discover if they, or members of their family had been convicted of a crime.
Results: forty-one per cent of the males were convicted of at least one offence between the ages of 10 and 50. The most important risk factors for offending were criminal behaviour in the family, low school achievement, poverty and poor parenting.
Conclusion: Situational factors lead to the development of antisocial behaviour.
Studies of the situational causes of APD
Elander et al
Aim: to investigate the childhood risk factors that can be used to predict antisocial behaviour in adulthood.
Method: researchers investigated 225 twins who were diagnosed with childhood disorders and interviewed them 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.