Experimental Methods

Experiments look for the effect that manipulated variables (independent variables, or IVs) have on measured variables (dependent variables, or DVs), i.e. causal effects.

Laboratory experiments

These pay particular attention to eliminating the effects of other, extraneous variables, by controlling them (i.e. removing or keeping them constant) in an artificial environment. This makes it more likely for researchers to find a causal effect, having confidence that no variables other than changes in an IV can affect a resulting DV. Laboratory experiments are the most heavily controlled form of experimental research.

Participants can also be randomly allocated to experimental conditions, to avoid experimenter bias (i.e. the experimenter cannot be accused of choosing who will be in each experimental condition, which could affect the results).

Field experiments

Field experiments are conducted in a natural setting (e.g. at a sports event or on public transport), as opposed to the artificial environment created in laboratory experiments. Some variables cannot be controlled due to the unpredictability of these real-life settings (e.g. the public interacting with participants), but an independent variable will still be altered for a dependent variable to be measured against.

Natural experiments

Natural experiments are studies where the experimenter cannot manipulate the IV, so the DV is simply measured and judged as the effect of an IV. For this reason, participants cannot be randomly allocated to experimental groups as they are already pre-set, making them quasi-experiments. For instance, an experiment might investigate the relative levels of aggression observed in boys and girls in a primary school (the experimenter cannot manipulate who belongs to the ‘boy’ and ‘girl’ groups).

Past Paper Questions

• Justify the use of the experimental method instead of case studies in cognitive psychology. (3) October 2016

• Describe a procedure Laurence could use for his study of memory. (4) June 2017

12 Marker

• Evaluate Mia and Felipe’s use of the laboratory experimental method in their investigation of memory. You must make reference to the context in your answer. (12)

• Evaluate whether Damon’s choice of a field experiment was a more appropriate method than Elisa’s choice of a laboratory experiment for this research scenario. (12) June 2018