Advantages of laboratory experiments:


1.      Experiments are the only means by which cause and effect can be established.  It has already been noted that an experiment differs from non-experimental methods in that it enables us to study cause and effect because it involves the deliberate manipulation of one variable, while trying to keep all other variables constant.  Sometimes the independent variable (IV) is thought of as the cause and the dependent variable (DV) as the effect.


2.      It allows for precise control of variables.         The purpose of control is to enable the experimenter to isolate the one key variable which has been selected (the IV), in order to observe its effect on some other variable (the DV); control is intended to allow us to conclude that it is the IV, and nothing else, which is influencing the DV.


3.      Experiments can be replicated.  We cannot generalise from the results of a single experiment.  The more often an experiment is repeated, with the same results obtained, the more confident we can be that the theory being tested is valid.  The experimental method consists of standardised procedures and measures which allow it to be easily repeated.


4.      It is also worth noting that an experiment yields quantitative data (numerical amounts of something) which can be analysed using inferential statistical tests.  These tests permit statements to be made about how likely the results are to have occurred through chance.



Limitations of laboratory experiments:


1.      Artificiality:  The experiment is not typical of real life situations.  Most experiments are conducted in laboratories - strange and contrived environments in which people are asked to perform unusual or even bizarre tasks.  The artificiality of the lab, together with the 'unnatural' things that the subjects may be asked to do, jointly produces a distortion of behaviour.   Therefore it should be difficult to generalise findings from experiments because they are not ecologically valid (true to real life).   


2.      Behaviour in the laboratory is very narrow in its range.  By controlling the situation so precisely, behaviour may be very limited. 


3.      A major difficulty with the experimental method is demand characteristics.   Some of the many confounding variables in a psychology experiment stem from the fact that a psychology experiment is a social situation in which neither the Subjects or the Experimenters are passive, inanimate objects but are active, thinking human beings.  Imagine youíve been asked to take part in a psychology experiment.  Even if you didnít study psychology, you would be trying to work out what the experimenter expected to find out.  Experimenters too have expectations about what their results are likely to be.  Demand characteristics are all the cues which convey to the participant the purpose of the experiment.



4.      It has already been noted that a strength of the experimental method is the amount of control which experimenters have over variables.  However it must also be noted that it is not possible to completely control all variables.  There may be other variables at work which the experimenter is unaware of.  In particular, it is impossible to completely control the mental world of people taking part in a study.