looked for age changes and differences in a sample of men and women
initially over 46 years old, who represented not only a different geo -
graphic region but also a somewhat broader range of socioeconomic sta -
tus. These researchers also reported that their subjects improved on the
second testing of intelligence, but they found neither cross-sectionaldifferences nor longitudinal changes in social independence. Thus, theapparent decline in Extraversion was not replicated across methods (itwas found in longitudinal but not cross-sectional analyses), facets(social independence but not other Extraversion scales), or samples(Boston but not Duke). Since replication is the foundation of scientificinference, the case for change in that personality trait seems closed.
The Duke investigators also reported an anomalous finding: Al -
though there were no cross-sectional differences in Guilt-proneness, a
scale that measures an aspect of Neuroticism, they found that with timemen tended to score lower and women higher on this scale. None of theother Neuroticism scales showed the same pattern, nor did the men inthe Boston study become less guilt-prone with age. Again, we concludethat this finding can best be ascribed to chance.
Most importantly , the Duke study confirmed the Boston study in
finding overwhelming evidence of stability . It found no longitudinalchanges in the degrees to which subjects were outgoing, emotionallystable, assertive, happy-go-lucky , conscientious, adventurous, tender-minded, suspicious, imaginative, shrewd, liberal thinking, independent,controlled, or tense.
SEQUENTIAL STRATEGIES:
AVOIDING PRACTICE AND TIME EFFECTS
Longitudinal methods, we have pointed out, are free from some of the
problems of cross-sectional studies, but they have other problems oftheir own. One of these we have already encountered in discussing thechanges in intelligence seen in the Boston and Duke studies. Whenindividuals take the same test repeatedly , they may answer differentlysimply as a result of exposure to the test. When an ability test is in -
volved, this is called a practice effect , and that term has also been used to
describe other effects of repeated measurement. For example, peoplemay find a personality test less threatening the second time and givemore candid answers. Or they may find it boring and become careless.Growth or Decline in Personality 71