Understanding Psychology (10th Ed)

E VA LU AT E
1. Developmental psychologists are interested in the effects 
of both 
and 
on development.
2. Environment and heredity both infl uence development 
with genetic potentials generally establishing limits on 
environmental infl uences. True or false?
3. By observing genetically similar animals in differing envi-
ronments, we can increase our understanding of the infl u-
ences of hereditary and environmental factors in humans. 
True or false?
4.
research studies the same individuals over a 
period of time, whereas 
research 
studies people of different ages at the same time.
differences, any age differences we fi nd in a cross-sectional study may refl ect edu-
cational differences among the cohorts studied: People in the older age group may 
belong to a cohort that was less likely to attend college than were the people in the 
younger groups. 
A longitudinal study, the second major research strategy developmental psy-
chologists use, provides one way around this problem.  Longitudinal research  traces 
the behavior of one or more participants as the participants age. Longitudinal stud-
ies assess change in behavior over time, whereas cross-sectional studies assess differ-
ences among groups of people.

For instance, consider how we might investigate intellectual development during 

adulthood by using a longitudinal research strategy. First, we might give an IQ test 
to a group of 25-year-olds. We’d then come back to the same people 20 years later 
and retest them at age 45. Finally, we’d return to them once more when they were 
65 years old and test them again. 
By examining changes at several points in time, we can clearly see how indi-
viduals develop. Unfortunately, longitudinal research requires an enormous expen-
diture of time as the researcher waits for the participants to get older. Participants 
who begin a study at an early age may drop out, move away, or even die as the 
research continues. Moreover, participants who take the same test at several points 
in time may become “test-wise” and perform better each time they take it because 
they have become more familiar with the test. 
To make up for the limitations in both cross-sectional and longitudinal research, 
investigators have devised an alternative strategy. Known as  sequential research,  it 
combines cross-sectional and longitudinal approaches by examining a number of 
different age groups at several points in time. For example, investigators might exam-
ine a group of 3-, 5-, and 7-year-olds every six months for a period of several years. 
This technique allows a developmental psychologist to tease out the specifi c effects 
of age changes from other possibly infl uential factors.