Laboratory experiments and eyewitness testimony
- A laboratory experiment creates a situation in which one (or more) variable(s) are altered whilst all others are kept constant
- This is possible as laboratory conditions allow the researcher to deliberately manipulate the independent variable (IV). The effect of the IV of the dependent variable (DV) can be measured accurately
- In the case of studies of eyewitness testimony, an aspect of the witnesses’ experience is manipulated and the accuracy of their recall is measured. Other variables, such as the length of exposure to the ‘crime scene’, the ease with which each individual can see the events and the time over which they have to remember details, are kept the same
- In experiments on eyewitness testimony, the experimental design is usually independent groups. For example, in Loftus and Palmer (1974), different participants heard each of the verbs.
- In addition to setting up experimental conditions, it is also possible to have a control group — a condition in which the IV is absent. This acts as a baseline against the changes in the DV.