Discuss the tradeoffs between internal and external validity


Start by reviewing Table 9-4 (p. 276). Then, ask students to debate whether researchers are too eager to trade external validity for internal validity.

Students tend to believe that researchers overemphasize internal validity (although students are more accepting of these tradeoffs in fields such as sensation/perception than in fields such as social/personality). Students often point to the extensive use of college students and animals as participants in psychological research. Therefore, prior to the debate, you will want to emphasize the extent to which physical sciences value internal validity as well as the value and difficulty of establishing internal validity. In addition, you may want to have students read the following articles.

Anderson, C. A., Lindsay, J. J., & Bushman, B. J. (1999). Research in the

psychological laboratory: Truth or triviality? Current Directions in

Psychological Science, 8, 3-9.

Banaji, M. R. & Crowder, R. (1989). The bankruptcy of everyday memory.

American Psychologist, 44, 1185-1193.

Berkowitz, L. & Donnerstein, E. (1982). External validity is more than skin deep.

American Psychologist, 37, 245-257.

Mook, D. G. (1983). In defense of external invalidity. American Psychologist,

38, 379-389.

Stanovich, K. E. (1990). How to think straight about psychology. Glenview, IL:

Scott, Foresman.


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