Main testing effect:

One of the types of testing effects which may be presented in an experimental design. The main testing effect occurs when a prior observation (pre-measurement) affects a latter observation (post-measurement). As a result of main testing effect, post-measurement attitudes are influenced more by pre-measurement attitudes than by the independent variable itself. The main testing effect may also be reactive, causing the respondents to change their attitudes simply because these attitudes have been measured. The main testing effect compromises the internal validity of the experiment.