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While internal validity refers to conclusions drawn about events that occurred within the
experiment, external validity refers to the extent to which the results of a research design can be
generalized beyond the specific way the original experiment was
conducted. Generalization refers to the extent to which relationships among conceptual variables
can be demonstrated in a wide variety of people and a wide variety of manipulated or measured
variables.
Psychologists who use college students as participants in their research may be concerned about
generalization, wondering if their research will generalize to people who are not college students.
And researchers who study the behaviors of employees in one company may wonder whether the
same findings would translate to other companies. Whenever there is reason to suspect that a
result found for one sample of participants would not hold up for another sample, then research
may be conducted with these other populations to test for generalization.
Recently, many psychologists have been interested in testing hypotheses about the extent to
which a result will replicate across people from different cultures (Heine, 2010). [5] For instance,
a researcher might test whether the effects on aggression of viewing violent video games are the
same for Japanese children as they are for American children by showing violent and nonviolent
films to a sample of both Japanese and American schoolchildren. If the results are the same in
both cultures, then we say that the results have generalized, but if they are different, then we
have learned a limiting condition of the effect (see Figure 2.19 "A Cross-Cultural Replication").
Figure 2.19 A Cross-Cultural Replication