Artificiality: The tension between internal and external validity in economic experiments

The artificiality of a laboratory situation is placed in the context of the tension between external and internal validity. Most economists consider internal validity to be most important. A proper evaluation of the ?artificiality criticism? (a lack of external validity) requires distinguishing the various goals experimentalists pursue. External validity is relatively more important for experiments searching for empirical regularities than for theory?testing experiments. As experimental results are being used more often in the development of new theories, a methodological discussion of their external validity is becoming more important.