Understanding Psychology (10th Ed)

 Module 
28 
Group Diff erences in Intelligence: Genetic and Environmental Determinants 
303
scores have risen signifi cantly—a phenomenon named the Flynn effect after its dis-
coverer, psychologist James Flynn. The Flynn effect is not trivial, with the perfor-
mance of the average 20-year-old today measuring some 15 points higher than the 
performance of the average 20-year-old in 1940 (Flynn, 2000, 2007). 
The cause of the Flynn effect is not clear. Flynn and a colleague, economist Wil-
liam Dickens, argue that the higher scores have resulted as people have matched 
their genetic gifts with their environment. Because society is increasingly complex 
and driven by technology, it is increasingly making demands that people with high 
intelligence are particularly adept at meeting. Consequently, society provides greater 
opportunities for people with high IQs to excel, and that environment pushes them 
even more intellectually, creating an increase overall in IQ scores (Dickens & Flynn, 
2001; Flynn, 2007). 
Other explanations for the Flynn effect suggest that it may due to better nutri-
tion, better parenting, or improvements in the general social environment, including 
education. Whatever the cause, the change in IQ scores over the century is not due 
to evolutionary changes in human genetics: The period over which the Flynn effect 
has occurred is far too short for people to have evolved into a more intelligent spe-
cies (Loehlin, 2002; Sunder Borren, & Tambs, 2008; Lynn, 2009).
 PLACING THE HEREDITY–ENVIRONMENT QUESTION 
IN PERSPECTIVE 
Ultimately, there is no fi nal answer to the question of the degree to which intelligence 
is infl uenced by heredity and by the environment. We are dealing with an issue for 
which experiments to unambiguously determine cause and effect cannot be devised. 
The more critical question to ask, then, is not whether hereditary or environmen-
tal factors primarily underlie intelligence, but whether there is anything we can do 
to maximize the intellectual development of each individual. If we can fi nd ways to 
do this, we will be able to make changes in the environment—which may take the 
form of enriched home and school environments—that can lead each person to reach 
his or her potential.
Social and economic inequality, as well 
as heredity and other environmental 
factors, are associated with diff erences 
in intelligence. People who have greater 
educational opportunities and who 
suff er fewer economic constraints are 
able to maximize their intelligence.
feL82795_ch09_276-305.indd Page 303 7/31/10 2:30 AM user-f465
feL82795_ch09_276-305.indd Page 303 7/31/10 2:30 AM user-f465
/Users/user-f465/Desktop
/Users/user-f465/Desktop

---