COHORT

COHORT
A cohort refers to a group of people that were born
at the same period of time. They are likely to share
some common experiences such as social, cultural,
and historical influences that are unique to them.
Examples of well-known cohorts include ‘‘baby
boomers’’ and ‘‘Generation Xers.’’ Cohort effects
arise when changes in performance are due circumstances
specific to a particular time and place, rather
than age. Thus, if looking at physical development,
children born during times of conflict or war may
have retarded physical growth due to stress and food
deprivation. Therefore, growth pattern norms might
be inaccurate if based on this cohort. Another example
would be gender differences in vocational aspirations
for adolescents. Career choices by males and
females could depend on whether fifteen-year-olds
born in 1985 participated in the study versus fifteenyear-
olds born in 1935. Both cross-sectional and longitudinal
research designs are susceptible to cohort
effects. A cross-sequential design may be used when
cohort effects are suspected.
See also: DEVELOPMENTAL NORMS; STAGES OF
DEVELOPMENT
Bibliography
Miller, Scott. Developmental Research Methods, 2nd edition. Englewood
Cliffs, NJ: Prentice-Hall, 1998.
Katherine M. Robinson