Experiments

The experimental method

• An experiment sets about isolating cause and effect. The essential element is for the researcher to change the independent variable (IV) in order to see the effect on the dependent variable (DV). The DV responds to the IV and this response can be measured.
• You need to know three types of experimental method:
• - Laboratory experiment
• - Field experiment
• - Natural experiment

Laboratory experiments

• .A laboratory experiment usually takes place in a laboratory but it could be in a room. The essential criterion is that it takes place in highly controlled conditions so that the researcher can control all of the variables except the one that is changed between the experimental conditions
• .Strengths:
• The high level of control over the IV and DV means that extraneous variables are minimised.
• The high level of control allows the measurement of the effect, so that it is possible to establish cause and effect.
• can be replicated and repeated.
• Limitations:
• Not natural, no ecological validity, not realistic results.
• There are sometimes ethical issues with laboratory experiments as participants are being manipulated into behaving in ways that they would not normally act. Deception might have been used to manipulate behaviour and this leads to lack of informed consent.
• Due to the nature of the situation, participants and the researcher may change their behaviour. Participants may guess the nature of the study and may behave according to how they think they are expected to behave. Such demand characteristics may affect the DV and therefore invalidate the results.

Field experiments

• A field experiment is a study conducted in a natural environment. The researcher still has control over what he/she believes to be the cause. However, other factors (variables) could have an effect that may be either positive or negative.
• Strengths:
• High ecological validity.
• There are usually fewer ethical issues because participants behave more naturally in their own environment.
• Limitations:
• Replication is difficult, since it would be virtually impossible to recreate the exact situation. This has implications for validity in that the findings could be different in another situation.
• Can't control extraneous variables.

Natural experiments

• A natural experiment is a study where the IV is naturally occurring and cannot be manipulated by the experimenter. For example, researchers may want to investigate the effects of a disaster on post-traumatic disorder after a tsunami. The tsunami cannot be manipulated to suit the researcher.
• Strengths:
• Participants may be unaware that they are part of an experiment, since it evolves from a naturally occurring situation, and this means there is high internal validity.
• Natural experiments give researchers a chance to investigate a unique situation that cannot be engineered. It would be highly unethical even to try. Insight into behaviour under these circumstances can prove invaluable.
• Limitations:
• Can be unethical, they are unaware of the research taking place.
• Not replicable or repeatable.
• Can't control variables.