same underlying entity . The butterfly is the natural outgrowth of the
caterpillar, as different as the two are in form and function. The envi -
ronment may hasten or retard, facilitate or damage the transformation,
but caterpillars will never turn into spiders no matter what environ -
ments we impose on them. The same basic genetic material endures
through and is manifest in successive stages of development.
Most of the theorizing about the course of personality in the indi -
vidual has been offered by child developmentalists (J. H. Block & J.
Block, 1980; Kagan & Moss, 1962; Thomas, Chess, & Birch, 1968) in -
terested in accounting for personality from the period of infancy
through adolescence, although a few theorists have carried the ideathrough adulthood. The attempt to account for the origins of personal -
ity in childhood is immensely attractive, since childhood seems to be
the time when the most could be done to change or improve lifelongpatterns of adjustment. At the same time, it is an extraordinarily ambi-tious undertaking. It is easy enough to chart the course of Extraversion,say , in an adult: Simply have him or her fill out a questionnaire every 10years or so. But we cannot ask a 5-year-old to complete a questionnaire;we cannot ask an infant even a few simple questions. How , then, do wemeasure personality?—By observations of behavior? What kind of in-fant behavior corresponds to Openness to Aesthetic Experience or Duti-fulness? Is it even meaningful to ask about such dimensions of person-ality before adolescence?
Fortunately , we do not need to solve these problems here. Other
writers, more knowledgeable in the area, have struggled with them andoffered their own answers. The issue concerns us here, however, be -
cause the same answers may be useful in conceptualizing the course of
personality in adulthood.
One of the more elaborate models has been labeled the heterotypic
(ordifferent-form )continuity model (Kagan, 1971). Just as an insect goes
through four distinct but developmentally related stages, so too maypersonality evolve through a succession of distinct phases. Sociability inadulthood may be the consequence not of sociability in childhood butof some very different trait—say , academic interests. If we watched anunsociable but intellectual child develop into a warm and friendlyadult, we might believe that we had seen a failure of continuity . But ifwe watched a whole group of intellectual children become sociableadults, we would believe we had discovered a pattern, a kind ofdispositional metamorphosis. (We might then attempt to explain theThe Course of Personality Development 103