Biological studies Flashcards
What is the name and date of the twin study?
Brendgen et al 2005
What is the aim of the biological twin study?
The first aim was to see if social aggression would be caused by genes or the environment.
The second aim was to see if social aggression shared the same cause as physical aggression.
The last aim was to see if one type of aggression is able to lead to another type.
Who were the participants in the biological twin? What participant design was used?
Participants were recruited from the Quebec Newborn Twin Study and all were pairs of twins born between November 1995 and July 1998. At the start of the study 322 pairs of twins were tested but complete data was only gathered on 234 twin pairs.
- 44 pairs were MZ males
- 50 pairs were MZ females
- 41 pairs were DZ males
- 32 pairs were DZ females
- 67 pairs were mixed sex DZ twins
Describe the procedure of the biological twin study.
Data from the sample was gathered longitudinally at 5, 18, 30, 48 and 60 months of age and then again at 6 years. The data at 6 years is the one they focussed on. The data consisted of two ratings at each twins behaviour- one by their teacher and one by their classmates gathered in the spring term
Teacher ratings were based on agreement with a series of statements taken from items on the Preschool Social Behaviour Scale and the Direct and Indirect Aggression Scales. The scores given by the teachers were on a three point scale.
Peer ratings of the twins were done by giving each child in the twins’ classes a booklet containing photos of every member in the class. Every child was then asked to circle three pictures of children that matched four different behaviour examples
Describe the results of the biological twin study.
The results showed that there was a much higher correlation between the ratings of the MZ twin pairs on physical aggression than between same sex DZ twins. Scores for social aggression were roughly equally correlated in MZ and DZ twin pairs. This shows that in relation to the first aim, physical aggression may be as a result of genetic factors whereas social aggression might be explained by environmental factors.
The data suggested that physical aggression may lead to social aggression but not the other way around. As young children they are only able to express this physically but as language and cognitive skills develop, so do their abilities to express aggression in new ways.
Evaluate the biological twin study in terms of generalisability.
The study is low in geralisability. A very small sample of ages when looking at the different groups. Asking 6-year olds to provide ratings before they can read and write thermselves meant that the researchers had to record the data with each child. This was a time consuming process and resulted in the small sample size. Therefore the sample isnt an accurate representation of the entire population.
Teh age group studied is very specific. It would be impossible to assume that aggression in other age groups will have the same cause. Research has found that physical aggression reduces when children start school whilst social aggression does not fully develop until age 8. This suggests that aggression in older children or adults may be characterised very differently.
Evaluate the biological twin study in terms of reliability.
There could be many extraneous variables in the lives of this specific group of twins. However, the researchers themselves justified this criticism by saying that the cost in time and effort associated with individually measuring the twins behaviour across 409 different classrooms meant that selecting an assessment of moderating factors would have been difficult
Evaluate the biological twin study in terms of applications.
Theres potential for reseach findings to be used to help prevent children from later expressing aggression socially. It could be used as an early indicator to parents or teachers that a child may show problematic behaviour. This means it can be intervened early on rather than wait for it to become a habit. It would be much easier to challenge aggressive behaviour when a child is still learning.
Evaluate the biological twin study in terms of validity.
High in validity. The study benefits from taking measures of the twns aggressive behaviour from two different sources; teachers and peers. Researchers looked at two different sources of information which should eliminate any bias. The fact that teachers and peers were in good agreement with eachother adds to the validity of the findings. It would suggest that neither peers nor teachers were giving a biased view on aggressive behaviour.
What is the name and date of the biological adoption study.
Heston (1966)
What is the aim of the biological adoption study?
The aim of the study was to see how many adopted children of biological mothers with schizophrenia woud go on to develop schizophenia themselves. If a significant number did so, this would constitute powerful evidence for a role of genes in schizophrenia.
Who were the participants in the biological adoption study? What participant design was used?
The experimental subjects were born between 1915 and 1945 to schizophrenic mothers confined to an Oregon State psychiatric hospital. These children had been adopted at birth. A matched group of 50 adoptees whos mothers were believed to be mentally healthy were also identified. the control subjects were matched for sex, type of placement, and for length of time in care.
Describe the procedure of the biological adoption study.
They were asked to take part in a standardised interview. Part of the interview was to see if any of them had gone on to develop schizophrenia themselves. The information excluding genetic and institutional information was evaluated blindly and independently by two psychiatrists. A final evaluation was made by a third researcher.
Describe the results of the biological adoption study.
Of the 47 adults interviewed whose mothers suffered schizophrenia 5 had been hospitalised with schizophrenia. Three of these were chronically ill. This 10% of the adopted children of schizophrenic mothers developed schizophrenia. None of the control groups developed schizophrenia, indicating the experience of adoption was not a factor in schizophrenia.
What was the conclusion of the biological adoption study?
The results provided powerful evidence for the role of genes in schizophrenia. No evidence emerged from the study of any role at all for environmental factors in the development of schizophrenia
Evaluate the biological adoption study in terms of reliability.
The study is high in reliability and low in researcher bias. There was good aggrement between the raters. When differences arose, a fourth psychiatrist was asked for an opinion. This limited researcher bias and objectivity was established.
