cause the most disagreeable members of their generation have already
died. Agreeableness itself need not increase with age in order to find across-sectional age difference.
Cohort Effects
Spurious age differences in cross-sectional studies can also result fromgenerational or birth-cohort effects. When we make cross-sectionalcomparisons, we are in effect assuming that the young people of todaywill eventually come to resemble the current generation of older people.In some respects, such as the increased incidence of baldness, they al -
most certainly will. But we do not know whether they will also have the
same attitudes, same habits, or the same personality as today’s elderly .In short, we do not know whether personality is shaped more by agingor by cohort factors, by intrinsic maturation or by the social history ofspecific generations of people.
In the early days of personality theory , under the influence of
Freud’s models of development, it was assumed that personality wasformed early in life as the result of a complex series of interactions be-tween child and parents. Overly rigorous forms of toilet training andgeneral discipline were held to be the source of fixations, inhibitions,and neuroses in later life. Whereas Freud himself never advocated sucha simple relationship, many psychologists, pediatricians, and educatorscame to the conclusion that we would all be more emotionally healthy ifwe were given more freedom as children. Dr. Benjamin Spock’s (1946)immensely influential writings on child care took a step in this direc -
tion, and books such as Neill’s (1977) Summerhill showed what child -
hood could be like in an atmosphere of freedom. Over the past half-
century , corporal punishment has almost disappeared from schools andhas certainly declined in most households. Indeed, many psychologistsand educators today are calling for a return to firmer discipline, just asNeill tried to distinguish between “freedom” and “license.”
The point is not that today’s form of discipline is better or worse
than that enjoyed by children 50 years ago—the point is that it is de -
monstrably different. According to the basic tenets of some forms of
personality theory , this difference in the treatment of children ought tohave the most dramatic consequences for their adult personality . If childrearing changes across generations and if adult personality depends onchild rearing, different generations should show major differences inGrowth or Decline in Personality 65