|Are you smarter if you have a bigger brain?
|Question Date: 2008-03-18|
In short, size does not matter. Also,
intelligence is not just one ability. Rather,
there are different types. For example, there is
spatial intelligence (how good we are at
remembering where things are, moving things in our
'mind'), verbal intelligence, and emotion
intelligence to name just a few.
also research that shows when we disconnect the
tissue of the brain (which is called the corpus
callosum) that connects the left and right
hemispheres, individuals are able to function
normally. This shows that we don't the two parts
of the brain two works together all the time.
Intelligence in animals is largely a
function of the complexity and sophistication of
the connections between sense organs and activity
organs such as muscles. Having more nerve tissue
allows you to have a more sophisticated algorithm,
but does not imply it.In animals, the general rule
for intelligence is the ratio of brain size to
body size, since you need more nerve tissue to
coordinate more body mass, but even so, this is
hardly a definite algorithm. Squids and octopuses
are far more intelligent than most herbivorous
mammals, despite having substantially smaller
brains, even relative to their body mass.
Nope--cows have bigger brains than we do, and
they're not very smart. It's all about connections
in the brain. You do need a certain minimum size
of brain for particular tasks, which is why things
like emotion, analysis, art, and mathematics. But
it's mostly how complex the "wiring" is. Your
brain makes new wiring for each thing you learn.
Most of the wiring is your neurons (brain cells)
making new connections to each other.
The question of to what extent brain size and
intelligence are related is complicated. Brain
material is very energetically demanding. In
modern humans,the brain comprises only 2% of the
total body weight, but consumes roughly 20%of the
bodys oxygen and caloric budget. This high cost is
justifiable as we use our brains to perform
complex cognitive exercises. By comparing
different species we can see that when the
successful exploitation of the environmental
requires higher brain functions, we see the
evolution of larger brains. In bats, for instance,
those species that live in forested areas, where
there are more obstacles to avoid when flying,
brains are typically larger than in those species
that hunt in open areas. This is presumably as the
brain needs to be able to process more sensory
information in the more complex habitats. If you
look at the brain size of the species that led up
to modern day humans there isa clear pattern of
increase over time. This would not have come about
unless those individuals with larger brains were
more successful (for instance at hunting, making
tools, communicating, etc) than those with smaller
brains. Large brain size, however doesnt tell us
everything about intelligence. The species with
the largest brain by volume isnt humans (average
volume 1400cubic centimeters), but sperm whales
(average volume 9000 cubic centimeters). However,
due to their large size, sperm whale brains
comprise only 0.02% of their total body weight.
Large brain size also doesnt mean that a species
will necessarily do better than species with a
smaller brain. For instance,Neanderthals (a sister
species to modern humans from the genus Homo), had
on average larger brains than do anatomically
modern humans, but still went extinct (there is,
however, some debate amongst scientists whether
some Neanderthals interbred with anatomically
modern humans and thus disappeared though genetic
absorption). Nevertheless, it would appear that,
overall, brain size (as measured as a percentage
of body weight) is related to the ability to
perform complicated cognitive tasks.
Great question, but tough to answer. If we are
comparing two individuals of the same species,
then we need to think about what specific "parts"
of the brain might be related to "being smarter."
Also, it's difficult to define "smarter," so that
makes it tough to get at this kind of question.
Lots of people have asked this type of question
though. In fact, Albert Einstein (who we all agree
was "smart") donated his brain for such a study
-his preserved brain was just recently re
evaluated using new techniques and although his
brain was not substantially "bigger" overall,
there were parts that had slightly different
structures and surface areas. The higher cognitive
function areas were much more "developed" than a
"typical" brain. But again, it can be difficult to
know what "typical" means. So, although there are
some studies out there, I'd have to say we don't
really have an answer to your question except that
brain weight is not correlated precisely with IQ
(just one measure of "smartness, which is
But you can also think
about your question comparing across species.
Let's compare humans to a chimpanzee. Whatever
distinguishes human primates from other animals
must reside in the unique features of human
development, especially in development of the
brain. There are at least 5 features that
distinguish human brain development from that of
1. Retention of fetal neuronal
growth rate after birth.
2. Migration of cells
from pro encephalon to diencephalons (you can look
at a "brain atlas" to see these parts.
Activity of transcription (gene expression) - it's
much higher in humans.
4. Presence of a
specific form of the FOXP2 gene (critical for
5. Continuation of brain
maturation into adulthood.
This last one is
the "size" aspect - human brains keep growing well
into early adulthood while in chimps (for example)
the brain hardly grows at all after
I'll leave you with a quote that I
love, basically asking "can my brain figure out
its own mystery?"
"What is perhaps the most
intriguing question of all is whether the brain is
powerful enough to solve the problem of its own
creation [during embryonic development through
childhood]."Gregor Eichle (1992).
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