these studies painted a dismal picture of old age: The older people were
rigid, depressed, less intelligent, less mentally healthy , and so on. Thefact was somehow forgotten that college students represented the eliteof their generation whereas nursing home residents were by and largethe worst off of theirs. If we were to extrapolate from these cross-sectional findings, we would discover, for example, that by the time weare in our 8Os we will only have had an 8th-grade education! Errorsthis obvious are rarely made today . But sampling still presents problemsat whose magnitude we can often only guess.
Part of the problem stems from the fact that researchers tend to be
specialists. Personality psychologists are expert at constructing scalesbut tend to be less concerned with sampling. Sociologists and epidemi -
ologists are meticulous about their sampling strategies but may have
limited knowledge about psychometrics and are often constrained bythe time limitations imposed by the interview format they favor. Rarelydoes a gerontologist combine both sets of skills in looking for age differ-ences, so real progress often depends on collaborative work amongmany scientists from different disciplines.
A good example is the National Health and Nutrition Examination
Survey I Follow-up Study , or NHANES (Cornoni-Huntley et al., 1983).Originally designed to provide basic information on Americans’ health,this survey was made the basis for a nationally representative study ofaging. More than 10,000 adults ranging in age from 35 to 85 were sur-veyed between 1981 and 1984; included in the interviews were shortscales to measure Neuroticism, Extraversion, and Openness (Costa &McCrae, 1986b).
Figure 2 summarizes the results of cross-sectional analyses for
Black and White men and women. It is obvious that the lines are essen -
tially flat, showing only tiny declines across five decades. (Because of
the huge sample size, even these slight effects are statistically signifi -
cant.) Data from this representative sample replicate other cross-sectional
findings of lower Extraversion among older subjects, but they alsounderscore the limited magnitude of the age differences. It would seema little foolish to concoct a theory of age and personality around theeffects seen in Figure 2. But we have not yet heard the last of them.
Agreeableness and Conscientiousness were not included in the
NHANES study , so we do not know what pattern they would haveshown in a representative sample. Even if the cross-sectional increasesin Agreeableness we reviewed earlier had been replicated, however, itGrowth or Decline in Personality 63