(not finished) Discuss how and why particular research methods are used at the biological level of analysis

Correlational studies
Correlational studies focus on the possible relationship between a behaviour and inherited traits. This relationship is called the amount of heritability that a behaviour has. Correlational studies are often sued in studies involving twins and they do not involve manipulation of an independent variable. Many correlational studies look at to what extent the pairs of individuals share a behaviour. It tests the relationship between two variables of interest. The correlation is expressed as a number between -1 and +1. This number is called correlation coefficient. A correlation coefficient of 0 means that there is no correlation.
Positive correlation is when both variables are affected in the same way.
Negative correlation is when one variable increases and the other decreases.
Bidirectional ambiguity is the concept that in a correlational study, since no independent variable is manipulated, it is impossible to know if x causes y, y causes x, if they interact to cause behaviour, or whether it is just coincidental and no relationship truly exists.

Strengths:
- They are easy to conduct and produce data that allows for a comparison between two variables.
- They allow researchers to study variables that cannot be manipulated.

Limitations:
- They do not show cause and effect because they are non-experimental.

Case studies
A case study is an in-depth investigation of an individual/group to obtain a deep understanding of behaviour. Case studies are often used to find a relationship between the brain and a specific behaviour. This can be studied through the use of PET and/or MRI scans.

Intrinsic case study is where the study itself is of primary interest in the exploration.
Instrumental case study is the study of a case to provide insight into a particular issue, redraw generalisations, or build theory.
Descriptive case study generates a detailed description of a phenomenon. It is believed that such a description will in itself generate new knowledge. The findings of the descriptive case study are not analysed in terms of existing theory.
Explanatory case study describe and find possible explanations for the phenomenon under investigation. This includes theoretical analysis based on existing theory, or generation of new thoery based on the data.

Strengths:
- Opportunity to investigate phenomena that could not be studied otherwise
- Permits insight into social processes in a group
- Stimulates new research
- Contradicts established theory and helps to develop new theories

Limitations:
- Difficult to define a case study
- Researcher bias
- Memory distortions and effects of social desirability

Laboratory experiments
Laboratory experiments involve identifying a cause and effect relationship between two variables and needs to be performed in a controlled environment of a laboratory in order to control other variables.

Strengths:
- The experiments usually show a cause-and-effect relationship
- Complex brain scanning equipment can be used easily
- The precise nature of the experiment allows for replication by other researchers, which provides a check on the reliability of the results.

Limitations:
- There's a lack of ecological validity
- The internal validity of experiments is low

Field experiments
The experiment takes place in a natural environment, but the researchers still manipulate variables.

Strengths:
- They are more ecologically valid because there is less artificiality

Limitations:
- The lack of control over variables is the main drawback and can result in a lack of confidence in the results

Natural experiments
The experiment where the researchers have no control over the variables.

Strengths:
- They can be used in settings where it otherwise would be ethically unacceptable to manipulate the independent variable

Limitations:
- Replication is almost impossible because the researcher does not control neither the independent variable nor the allocation of participants to groups