Experiments are widely used in psychology because they enable the researcher to collect data using various techniques, which should be chosen in line with what the researcher wants to find out. There are, however, some features that all experiments have in common, which are:
- The researcher manipulates an independent variable
- The researcher measures the dependent variable
- The researcher attempts to control all other variables which may affect the results of the experiment
Experiments are set up by the researcher and they should be controlled as far as possible so that it is clear that any results are as a result of what has been manipulated by the researcher and not something else. This helps to establish cause and effect because any variable, other than the independent variable, should have been controlled and therefore not influence the outcome of the research.
There are three main types of experiment:
- A laboratory experiment: this type of experiment takes place in a well-controlled environment. The researcher decides where the experiment will take place, at what time, with which participants, in what circumstances and using a standardised procedure. This type of experiment is most suitable for research where extraneous variables would be problematic, such as when testing memory and participants could be distracted by light, noise and temperature, all of which can be controlled by this method
- A field experiment: this is an experiment carried out in a real-life setting. Researchers do not have control over the environment but they still control key variables. Social psychology experiments are often carried out by use of this method, as it is less artificial than working in a laboratory. For example, they might take place in a street, a hospital or playground
- A natural experiment: this type of experiment also takes place in a real-life setting, but unlike a field experiment, the researcher has no control over either the environment or the variables. The IV, therefore, is likely to be naturally occurring. This method is most suitable for studies where there are questions about ethics or for longitudinal studies, such as the development of children
| Type of research method | Strengths of this method | Weaknesses of this method |
|---|---|---|
| Laboratory experiment | Easy to replicate.High level of control, which allows cause and effect to be established. | Low level of ecological validity because the environment is artificial.Participants tend to show demand characteristics because they know that they are taking part in an experiment. |
| Field experiment | High level of ecological validity as it is carried out in a real-life setting.There is less chance of demand characteristics, particularly if the research is covert, i.e. the people taking part in it are not aware of this until afterwards. | There is less control over extraneous variables, which may affect the results and make it more difficult to establish cause and effect. |
| Natural experiment | Very high levels of ecological validity, as behaviour will be more natural in this setting.Much less chance of demand characteristics, as like with field experiments, participants may not know that they are being studied.Can be used where it would be ethically questionable to manipulate the independent variable, such as deliberately causing stress to someone in a laboratory experiment. | Can be very expensive and time consuming.No control at all means that extraneous variables are much more likely to affect the results and it is difficult to replicate the study. |
