PSYC 489A--Special Topics: Human Behavioral Genetics
Coastal Carolina University--Fall 2003--Dr. King

Lecture 16a--Additional Notes on "Murrnstein"

The following comments refer to the transparency I showed in class on Monday,
Oct. 13th. The graphs on that transparency are reproduced on the handout I gave 
the following Wednesday and which you can find copies of on my office door.

Graph 1
Early in the 20th century, a minority of people graduated from high school, and
only about 2% graduated from college. Thus, the "general society" of noncollege
grads was a mixture of people of differing abilities (IQs). But around 1920, 
this started to change, and by 1990 the percentage of people getting college 
degrees was over 30%.

Graph 2
Early in the 20th century (see line marked "Mid 1920s"), colleges were less
selective based on IQ, so that people with IQ scores from the 20th through the
80th percentile were roughly equally represented. By the 1960s, this had 
changed. By the 1980s the trend had become even more pronounced, so that people 
in the lower percentile ranks of IQ were less likely to attend college, while 
people in the higher percentile ranks were much more likely to do so.

Graph 3
This graph shows a similar thing for high school grads in the top quartile of IQ
(i.e., in the top 25%). Up until 1950, about 55% of these people could be
expected to attend college. Starting about 1952, however, this percentage
started rising steeply, until by 1980 it was over 80%.

Graph 4
This graph shows that what "Murrnstein" refers to as cognitive sorting continues
through college, so that students completing a bachelor's degree are even more
strongly stratified by IQ. The chance that someone in the lower half of the IQ
distribution will complete college is low, but thereafter the percentage of
students completing college rises sharply.

Graph 5
These frequency distributions compare the IQ of people without college degrees
to those with. Notice that there is about 1 SD of difference between the two
distributions.

"Murrnstein's" point is that our society, largely through its educational
system, has become increasingly efficient at sorting people by intelligence.
People who score well on IQ tests typically go on from high school to college,
and most of them complete a college degree and consequently get well paying,
higher status jobs. People who score poorly on IQ tests typically don't go on
from high school to college, or if they do don't graduate, and therefore end up
in lower paying, lower status jobs. Thus, they argue, although it wasn't always
the case, society has in the last century become increasingly stratified by
intelligence (IQ). This trend has largely been driven by the way our educational
system works (which is largely driven by larger social forces). Since IQ is a
heritable phenotype, they argue that society is becoming genetically stratified
by these forces.

Note: these are "Murrnstein's" arguments (as nearly as I understand them) and do 
not necessarily reflect my own personal opinions on these issues. So don't get 
POed at me if you find this analysis objectionable.



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