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Journal Article Link 6.1: Mitchell, G. (2012). Revisiting Truth or Triviality: The External Validity of Research in the Psychological Laboratory. Perspectives on Psychological Science, 7(2), 109-117.

Anderson, Lindsay, and Bushman (1999) compared effect sizes from laboratory and field studies of 38 research topics compiled in 21 meta-analyses and concluded that psychological laboratories produced externally valid results. A replication and extension of Anderson et al. (1999) using 217 lab-field comparisons from 82 meta-analyses found that the external validity of laboratory research differed considerably by psychological subfield, research topic, and effect size. Laboratory results from industrial–organizational psychology most reliably predicted field results, effects found in social psychology laboratories most frequently changed signs in the field (from positive to negative or vice versa), and large laboratory effects were more reliably replicated in the field than medium and small laboratory effects.

1. Describe the external validity that was found for each psychological subfield and research topic
2. Why do you think the external validity varied by psychological subfield and research topic?
3. Why do you think large laboratory effects were more reliably replicated in the field than medium and small laboratory effects?

Journal Article Link 6.2: Garcia, F. M., & Wantchekon, L. (2010). Theory, External Validity, and Experimental Inference: Some Conjectures. The ANNALS of the American Academy of Political and Social Science, 628(1), 132-147.

Discusses ways to strengthen the external validity of an experiment through varied replication experiments that test multiple facets of the theory

It is often argued that experiments are strong on causal identification (internal validity) but weak on generalizability (external validity). One widely accepted way to limit threats to external validity is to incorporate as much variation in the background conditions and in the covariates as possible through replication. Another strategy is to make the theoretical foundations of the experiment more explicit. The latter requires that we develop trajectories of experiments that are consistent with a theoretical argument. In other words, new experiments should not simply consist of changing the context of old ones, but do so in ways that explicitly test various aspects of a theory in a coherent way.

1. What is the main idea of this article?
2. What do the authors argue are strategies to improve external validity of research studies?
3. What are the advantages and disadvantages of these strategies?
4. Do you think internal or external validity is more important? Why?