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Experiment
A research method used by psychologists which involves the manipulation of Variables in order to discover cause and effect.
A considerable amount of psychological research uses the experimental method, especially the Laboratory experiment. This method differs from non-experimental methods in that it involves the deliberate manipulation of one variable, while trying to keep all other Variables constant.
The variable which is being manipulated by the researcher is called the independent variable and the Dependent Variable is the change in Behaviour measured by the researcher.
All other Variables which might affect the results and therefore give us a false set of results are called confounding Variables (also referred to as Random variables).
By changing one variable (the independent variable) while measuring another (the dependent variable) while we control all others, as far as possible, then the experimental method allows us to draw conclusions with far more certainty than any non-experimental method. If the IV is the only thing that is changed then it must be responsible for any change in the dependent variable.
Many experiments are carried out in Laboratory conditions but it is possible to carry out experiments in the field – away from the laboratory. An example of this is the field Experiment carried out by Piliavin et al. (1969) in which they arranged for a person to collapse on an underground train and waited to see how long it was before the person was helped. One of the independent Variables they used was the appearance of the ‘victim’. That is whether he was carrying a walking stick or whether he appeared to be drunk.
As with the Laboratory experiment, the independent variable is still deliberately manipulated by the researcher. However it is not possible to have such tight control over Variables in the field, but it does have the advantage of usually being far less artificial than the laboratory.
Psychologists can take advantage of a natural situation in order to carry out an investigation in circumstances which they cannot themselves manipulate. This is called a natural Experiment because the researchers are taking advantage of a naturally occurring independent variable. For example, a college may decide to try out a completely new teaching approach and the effects of this could be compared with another college using a different teaching approach. Or a comparison of Moral Development could be made between children reared in Hull and Liverpool.
A natural Experiment is not a true Experiment because the researcher is unable to manipulate or control variables. For this reason it is sometimes referred to as a quasi experiment.
