Explanation
of the Flynn Effect
Copyright ã 1997, 2010 by James
Michael Howard.
(Added April 26, 2010: Maybe the
major part of my explanation of how DHEA is used by the brain is that various
parts of the brain compete for DHEA. As
is well known now, in the U.S. and maybe elsewhere, the frontal lobes develop
last. As the brain is exposed to
increased testosterone in utero, androgen receptors are formed which are
accessed by DHEA. This effect increases
androgen receptors which cause the competition for DHEA. If the brain exhibits increased androgen
receptors in parts of the brain other than the frontal lobes, then these areas
will exhibit increased competition for DHEA during childhood and adolescence
and increase in function. This
competition will reduce final growth and development of the frontal lobes while
increasing growth and development of other areas because of competition. I think this is why we are seeing increased
lack of impulse control in our youth.
(The frontal lobes control lower brain impulse control.) I think the same mechanism causes the Flynn
Effect. Again, I suggest this is caused
by this same mechanism, that is, while the frontal lobe is reduced in
competition for DHEA, other areas are increasing. Memory is improved in the Flynn Effect. An improvement in one area of the brain may
indicate that another may exhibit a decline.
This is why they Flynn Effect may be increasing simultaneously with
decreasing frontal lobe development. Our
populations are gaining in one area while we loose abilities in the very areas
that make us human. Humans are
characterized by impulse control. (Of
course, I think this ability is being reduced by the secular trend.)
Some
people think the Flynn Effect is a positive finding. I do not think so. I think it indicates that we are being
adversely affected by the increased exposure to testosterone. We are losing the ability to control impulses
because of increasing maternal testosterone which is producing many adverse
phenomena, such as increased morbidity, and the Flynn Effect. The Flynn Effect should be viewed as a
negative finding.)
The Flynn Effect refers to an increase in IQ
that occurs along with the secular trend. The secular trend is the increase in
size, height and weight, and the earlier onset of puberty in children. The
Flynn Effect is mainly an increase in scores on "non-verbal tests."
The overall effect is primarily due to increases in the lower half of the IQ
distribution, but it also occurs in the "gifted," or those who score
1400 or more on the SAT. The Flynn Effect is a worldwide phenomenon. (It occurs
in all socioeconomic groups.)
I suggest the Flynn Effect is due to rising
testosterone. The effect is small; perhaps 15 points in two generations. I
suggest that two kinds of increases in hominid brain size have occurred in
human evolution. One, that causes only slight
increases in brain size, I attribute to increasing testosterone in hominids.
This is the small increase noticeable in the early hominids. This is the
increase I think is due mainly to the increases in testosterone that started
separating us from the other primates. (Human males and females produce more
testosterone than chimpanzee males and females.) The main increase in hominid
brain size, I suggest, is due to the effects of the hormones, DHEA and
melatonin that occurred as hominids moved away from the equator. (Please read
my explanation of human evolution at this site for more detail.) The effects of
these two hormones, according to my theory, have to occur away from the
equator, and this is where the fossil evidence, north and south, shows the main
increases in brain size. The increase in testosterone will cycle through
hominids, i.e., testosterone will periodically rise in humans. It will produce
some dramatic effects, but one, I suggest, is a slight increase in nonverbal
abilities of the brain that will cause slight increases in overall IQ scores.
To explain this, I am including part of my "letter to the editor," in
The Morning News of Northwest Arkansas, May 14, 1995, regarding math and
English levels in American schools. This was generated in response to findings
that "reading proficiency is down in virtually 40 states ...and
significantly down in 10." The math scores were up lightly; this is the
Flynn Effect in the U.S., as of April, 1996. The increase in testosterone
causes the slight increases in nonverbal abilities, while it causes decreases
in verbal abilities. This letter explains the basics of my explanation of the
mechanism that produces the Flynn Effect.
"It is generally accepted that
the two sides of the brain (cerebral hemispheres) interact but basically
perform different functions. The things we call reading and writing are usually
controlled by the left half, mathematical things and spatial abilities are
usually located in the right half. Because of this divergence in function, boys
are, generally, but not always, better in math than girls. My work suggests a
reason for this that is directly connected to the changing reading and math
scores.
The left hemisphere finishes growth
a little after the right. My work suggests brain growth is particularly
dependent on the hormone, DHEA. (DHEA in extremely small quantities stimulates
formation and growth of the brain cells primarily used in thinking, neurons.)
Therefore, the left hemisphere depends on a continued supply of sufficient DHEA
for final growth. All Tissues, especially the brain, compete for DHEA. The hormone, testosterone, increases use of DHEA by testosterone
target tissues, which also includes parts of the brain. Boys produce
more testosterone than females so there is less DHEA, on average, for left
hemisphere growth. In animals studies, it has been
demonstrated that testosterone actually reduces development of the left
hemisphere (Behavioral and Neural Biology 1988; 49: 344).
Therefore, boys, on average, have an increased ratio of right hemisphere to
growth to left. The right side is used more for mathematical and spatial
thinking, therefore, on average, boys outperform girls
in these areas.
If you want to be a good
mathematician, you might be tempted to want more testosterone. In tests of
spatial and mathematical reasoning, males with high testosterone score much
worse than those with low testosterone. High testosterone increases lower brain
growth and development at the expense of even the right hemisphere. That is, in
high testosterone, even the right hemisphere looses in the competition for
DHEA.
I have suggested in past letters to
this paper that testosterone is rising in this society. Most people see it in
the 'secular trend,' that is, boys and girls are getting bigger and reaching
puberty earlier. If testosterone is rising, it not only will affect the size of
our children, but it will also affect their brains. That is, as testosterone
increases it will decrease the ratio of left hemisphere to right. This will be
seen, on average, as a decline in reading ability and an increase in math
abilities. In areas where testosterone is very high, reading and math scores
should both decline. The thing that worries me most is that one of my
references points out that 'the left hemisphere also seems to be the seat of
analytical thinking...' According to the National Assessment of Educational
Progress, we may be seeing a real, and in some areas already significant,
decline in functions of the left hemisphere."