Thomas, Chess and Birch (1977)
Aim: To discover whether individuals are constant in ways they respond to the environmnet throughout life.
Method: They studied 133 children form infancy to early adulthood. The childrens behaviour was observedand their parents interviewed. The parents were asked about their child's routine and reaction to change.
Results: They found that the children fell into 3 types: easy, difficult and slow to warm up to. The easy children were happy, flexible and regular. The difficult children were demanding, inflexible and cried a lot. The slow to warm up to children did not respond well to change to begin with but once they adapted they were usually happy.
Conclusion: These ways of responding to the environment stayed with the children as they developed. They therefor concluded that temperament is innnate.
Can't generalise to other social classes as all children where from mid-class and lived in NY. Parents may have been biased to their childrens behaviour. longitudinal study.
Buss and Polmin (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 3 dimentions of behaviour and compared the scores for each pair of twins.
- Emotionality: How strong the child emotional response was.
- Activity: How enrgetic the child was.
- Sociability: How much the children wanted to be with other people.
Results: There was a closer correlation between the score of the monozygotic twins.
Conclusion: Temperment has a genetic bias.
Cannot be generalise to the whole population as not everyone is a twin. monozygotic twins are treated similarly therefore explain the correlation could be explained by the environment and not their genes.
Kagan and Snidman (1991)
Aim: To investigate whether temperament is due to biological differences.
Method: They studied the reaction of 4 month of babiesto new situations. For the first minute the baby was placed in a car seat with the caregiver sitting by. For the next 3 minutes the caregiver moved out of the babies view while the baby was shown different toys by the researcher.
Results: 20% of babies showed disstress by crying,vigorous movement of arms and legs and arching their back. They were classes as high reactive. 40% of the children showed little movement or emotion. They were classed as low reactive. The remaining infants fell somewhere in between.
Conclusion: They concluded that these 2 temperaments are due to inherited differences in the way the brain responds.
They used a large sample which is easier to generalis. Set in an experimentalo setting. This has a high controlled environment but also lacks ecological validity.