proval of social groups as they aged but also why different generations
(or, as we will see, times of measurement) also influenced this variable.
Before exerting our creativity in looking for an explanation of this
curious finding, we should be sure there is really something here toexplain. The fundamental principle of science is reproducibility: A phe -
nomenon must be dependable, regardless of how or by whom it is
observed. Few phenomena in the psychological sciences show theinvariance of the laws of physics, because our constructs are moreabstract and less easily and accurately measured. But we have a right todemand that results be generally replicable—that most investigatorswill report the same general findings and that we can show them our -
selves using different measures or different groups of people. The fact is
that many so-called findings in psychology are the results of chance,and even the statistical methods that psychologists adopt do not protectthem from drawing the wrong conclusions once in a while. One alterna-tive, therefore, is to ascribe the longitudinal change in social indepen-dence to pure chance. The finding may be meaningless, a fluke.
There is some basis for thinking that this might be so. Social inde-
pendence is an aspect of introversion, and our finding might be taken asevidence that individuals become more introverted with age—an inter-pretation that supports some theories of aging. But the 16PF also hasseveral scales that tap other forms of Extraversion, and none of theseother scales showed a similar change in our sample. If we wanted tofind evidence of change (as many developmentalists do), we might ar-gue that independence happens to be the only aspect of Extraversionthat shows maturational change. In principle there is nothing wrongwith this hypothesis. If all Extraversion scales behaved identically , therewould be no reason to measure them separately . But notice that in orderto claim this longitudinal change as an age effect, we have to make tworather cumbersome assumptions: first, that the maturational changes donot show up in cross-sectional studies because of some mysterious con -
founding of generational differences with age changes; second, that
there is something special about independence that distinguishes itfrom other closely related scales that show neither the maturationalchanges nor the generational differences. Possible, but unlikely .
Fortunately , there is a much more direct way to find out if this was
a chance result. An independent longitudinal study carried on at DukeUniversity over a period of 8 years also employed the 16PF , although ina slightly shorter, simplified form (Siegler et al., 1979). Researchers70 PERSONALITY IN ADULTHOOD