Neuroscientists frequently
claim that minds come from brains. But this claim is simply a speech
custom of neuroscientists rather than anything they have established
through observations or experiments. When people attempt to produce
evidence to back up their claim that minds are made by brains, such
attempts do not hold up well to critical scrutiny. A recent such
attempt was a long review article in "The Scientist" magazine, one entitled “The
Biological Roots of Intelligence.” Let's look at why this article by
Shawna Williams fails to establish the claim that your thinking is
produced by your brain.
The first thing mentioned by
Williams is the Flynn Effect. She notes the following:
Children in Japan, for
example, gained an average of 20 points on a test known as the
Wechsler Intelligence Scale for Children between 1951 and 1975. In
France, the average 18-year-old man performed 25 points better on a
reasoning test in 1974 than did his 1949 counterpart.
But how could this be true if
our brains were producing our minds? There was no major change in
brains between 1949-1951 and 1974-1975. So the Flynn Effect is
actually hard-to-explain under the assumption that brains make minds.
The Williams essay then tells
us, “A recent study of 1,475 adolescents across Europe reported
that intelligence, as measured by a cognitive test, was associated
with a panoply of biological features.” But if you actually look at
that study, you will find it reports only a very slight relation
between intelligence and the brain. For example, the authors say
that a difference in gray matter in the striatum can account for less
than 1% of the variation in scores, and that a difference in
“polygenic scores” can account for less than 1% of the variation
in scores. After doing some more statistical analysis, some of these
faint effects seemed to disappear. The authors state “in this
additional analysis gray matter in striatum showed no significant
association” with IQ. At the end of their paper, the authors state
this about their study: “The effect sizes studied are small but in
the same range as previous studies (2.4% in previous structural
imaging studies and up to 4.8% for previous polygenic scores).”
Such very small percentages (of between about 1% and 3%) certainly do
not add up to any good evidence that your intelligence comes from
your brain.
One reason you should not at
all be persuaded by such small effects is that they could easily be
results that won't be replicated on a consistent basis. Imagine 20
different teams of neuroscientists comparing some group of brain
scans and genomes to the corresponding IQ scores. If one of the
teams of scientists check for 100 different things, they could easily
get a few slight apparent correlations purely because of random
variations in data that had nothing to do with a real biological root
of intelligence. It also could be that 9 out of 10 scientists
looking for such correlations find nothing, and don't bother to
publish their data (or have their papers rejected because of the bias
against null results). The 1 in 10 teams of scientists getting a
slight correlation because of random variations might be the ones who
end up getting their papers published.
Later Williams
refers to a study by Richard Haier that scanned the brains of people
while they were problem solving. But she quotes Haier as saying,
“The people with the highest test scores actually showed the lowest
brain activity.” Oops, this is the exact opposite of what we would
expect if our brains were producing our minds. Williams states,
“Some researchers are beginning to question the premise that the
key to intelligence can be seen in the anatomical features of the
brain.” Again, this is not something that inspires confidence in
the dogma that brains make minds.
Later in a box labeled
“Parsing Smartness,” Williams confesses, “The biological basis
for variations in human intelligence is not well understood.” Why
would that be if our brains were producing our minds? In the same
box we read this: “One well-known hypothesis, backed by evidence
from brain scans and studies of people with brain lesions, proposes
that intelligence is seated in particular clusters of neurons in the
brain, many of them located in the prefrontal and parietal cortices.”
But you do not explain how a brain could produce intelligence by
pointing to some part of the brain, and saying that such a part is
where the effect is coming from (just as I would not explain how I
could produce a thunderstorm if I told you that my thunderstorm
creation ability comes from my left thumb). The long-stated claim
that intelligence and judgment comes from the prefrontal cortex is
actually not well-supported by facts, as you can read about in this
long discussion of the evidence related to this claim, which
discusses many things that contradict such a claim.
In the same “Parsing
Smartness” box we read the following:
Researchers have also
proposed a slew of other hypotheses to explain individual variation
in human intelligence. The variety of proposed mechanisms underlines
the scientific uncertainty about just how intelligence arises.
From this it sounds like our
neuroscientists are vacillating all over the map, without any clear
basis for claiming that minds or intelligence comes from brains. The
Williams essay then has a quote from a neuroscientist, who says,
“General intelligence originates from individual differences in the
system-wide topology and dynamics of the human brain.” That's
just empty phraseology that means nothing. You don't explain how
people are able to think and understand by merely suggesting it comes
from “differences.”
Referring to the problem of
how intelligence arises, Williams states, “Santarnecchi finds
himself frustrated that research has not yielded more-concrete
answers about what he considers one of neuroscience’s central
problems.” Oops, sounds like our neuroscientists don't really have
any concrete reasons for believing in biological roots of
intelligence. Later the Williams essay states, “Von Stumm is
skeptical that genetic data will yield useful information in the near
term about how intelligence results from the brain’s structure or
function.” Such a statement seems to clash with the author's
claim that there are biological roots of intelligence.
Williams later states the
following: “In a meta-analysis published earlier this year, a team
led by then University of Edinburgh neuropsychologist Stuart Ritchie
(now at King’s College London) sifted out confounding factors from
data reported in multiple studies and found that schooling—regardless
of age or level of education—raises IQ by an average of one to five
points per year.” If that's true, even after
reaching adulthood each year of schooling raises your IQ. But why
would that be so if your brain was generating your mind? An adult's
brain doesn't get bigger when he is being educated. In fact, the
density of synapses in the brain sharply declines between the age of
12 and 22.
Next Williams refers to “the
biology of intelligence that remains a black box.” As every
computer programmer knows, a black box means some mysterious thing
you don't understand. Similarly, Williams later refers to the
“intractable phenomenon of intelligence.” But why would our
neuroscientists still not understand it if brains actually made
minds?
Shawna Williams was supposed
to be writing a long essay that would sum up all the best evidence
that intelligence comes from the brain. But she fails to produce any
convincing evidence for that dubious claim. And along the way,
several of the statements and quotes in her long essay give us reason
to doubt that there is any such thing as “biological roots of
intelligence.” It's not Shawna's fault. The problem is that the
evidence just doesn't really suggest that brains make minds. While
there are a few little things here and there which may seem to
whisper that maybe your brain makes your mind, there are other things
which speak in a louder voice that brains do not make minds. Among
many such things is the fact that hemispherectomy operations (in
which half of a brain is removed to stop seizures) do not usually have a major effect on intelligence, and the fact that a French man managed to long hold a job as a civil servant even when 90% of his brain was destroyed by disease.
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