76 aging and the life course, theories of

achievements across cohorts (Bernhardt et al.
2001). Criminology has developed trajectories
of criminal careers and their turning points in
varying contexts (Sampson & Laub 2003). And
social gerontology has steadily turned to esti
mating the influences of earlier life patterns,
including childhood origins, on later life eco
nomic well being and health (ORand 2001).
This convergence has not generated a uni
fying theory per se. Rather, efforts to develop
middle range theories within the life course
perspective continue. Some of these are
focused at the personological level. In this
vein, Glen Elder and his colleagues have pro
posed several mechanisms of human develop
ment across the body of his work (e.g., Elder
& Caspi 1990). The first two are borrowed
from Ryders (1965) classic paper on cohorts
and social change, the remaining from life
course research that has emerged over four
decades.

The life stage hypothesis: Social change
and historical events have enduring
(imprinting) impact on the lives of those
in vulnerable and/or transitional statuses
at the times of these events. The transition
to adulthood is especially fateful in its
long term effects.
The situational imperative hypothesis: The
level of disruption and compelling severity
of an event induces cohort variability.
Exposures to wars, to large scale depres
sions and similar big events, and to highly
disruptive proximate events such as family
dissolution, job loss, or incarceration, have
greater effects on the life course than less
severe events.
The interdependent lives hypothesis: Social
ties serve to diffuse experiences within a
cohort such that long term consequences
are felt not only by individuals with direct
experiences, but also by those associated
with these individuals. Families share each
others experiences.
The accentuation principle: New situations
increase the salience of prominent indivi
dual attributes and lead to their reinforce
ment and accentuation over the life
course. Ascribed attributes, and attributes
developed early in life (such as tempera
ment, aspiration, sociability), are reinforced
and amplified over the life course, and espe
cially in the face of adversity.
Other efforts are generating theories at a struc
tural level. One of the more provocative theo
retical developments in this regard addresses
life course stratification within cohorts based
on the cumulative dis/advantage hypothesis
(ORand 2002), which predicts that cohort dif
ferentiation over the life course is increasingly
stratified in the direction of initial inequality
(following Mertons Matthew Effect). Insti
tutional processes preferentially reward early
advantages and penalize early disadvantages
over time in a cumulative fashion. These pro
cesses are embedded in normative schedules of
achievement, organizational time clocks of
advancement, and socioeconomic compounding
and discounting regimes that cumulatively
appreciate or depreciate earlier achievements.
They are observable in patterns of economic
inequality and health disparities in mid and
late life in which socioeconomic origins and
early educational achievements exert enduring
independent effects on these later outcomes.
These factors become embedded in historical
contexts that can introduce obstacles to, or
incentives for, cumulative effects.
In short, the life course perspective has
been useful as an organizing framework for
the study of lives over time with its focus on
the intersection of biography with history. Its
usefulness has spanned research on diverse
domains of life, ranging from education to
family, work, health, and even criminal
careers. It has also spawned middle range
hypotheses to account for the changing tem
poral organization of lives over time.

SEE ALSO: Age, Period, and Cohort Effects;
Aging, Demography of; Aging, Longitudinal
Studies; Aging, Sociology of; Gerontology,
Key Thinkers; Life Course and Family; Life
Course Perspective

REFERENCES AND SUGGESTED
READINGS

Bernhardt, A., Morris, M., Handcock, M. S., &
Scott, M. A. (2001) Divergent Paths: Economic
Mobility in the New American Labor Market. Rus-
sell Sage Foundation, New York.