Physics 7

Preliminaries 15
• Intelligence is not even fixed within a population over time. A phenomenon known as “the
Flynn effect”15 (after its discoverer) suggests that IQ tests have increased almost six points a
decade, on average, over a timescale of tens of years, with most of the increases coming from
the lower half of the distribution of intelligence. This is an active area of research (as one might
well imagine) and some of that research has demonstrated fairly conclusively that individual
intelligences can be improved by five to ten points (a significant amount) by environmentally
correlated factors such as nutrition, education, complexity of environment.
• The best time for the brain to learn is right before sleep. The process of sleep appears to
“fix” long term memories in the brain and things one studies right before going to bed are
retained much better than things studied first thing in the morning. Note that this conflicts
directly with the party/entertainment schedule of many students, who tend to study early in
the evening and then amuse themselves until bedtime. It works much better the other way
• Sensory memory16 corresponds to the roughly 0.5 second (for most people) that a sensory
impression remains in the brain’s “active sensory register”, the sensory cortex. It can typically
hold less than 12 “objects” that can be retrieved. It quickly decays and cannot be improved
by rehearsal, although there is some evidence that its object capacity can be improved over a
longer term by practice.
• Short term memory is where some of the information that comes into sensory memory is
transferred. Just which information is transferred depends on where one’s “attention” is,
and the mechanics of the attention process are not well understood and are an area of active
research. Attention acts like a filtering process, as there is a wealth of parallel information in our
sensory memory at any given instant in time but the thread of our awareness and experience
of time is serial. We tend to “pay attention” to one thing at a time. Short term memory lasts
from a few seconds to as long as a minute without rehearsal, and for nearly all people it holds
4 − 5 objects17. However, its capacity can be increased by a process called “chunking” that
is basically the information compression mechanism demonstrated in the earlier example with
numbers – grouping of the data to be recalled into “objects” that permit a larger set to still
fit in short term memory.
• Studies of chunking show that the ideal size for data chunking is three. That is, if you try to
remember the string of letters:
with the usual three second look you’ll almost certainly find it impossible. If, however, I insert
the following spaces:
It is suddenly much easier to get at least the first four. If I parenthesize:
so that you can recognize the first three are all government agencies in the general category of
“intelligence and law enforcement” and the last three are all market symbols for information
technology mega-corporations, you can once again recall the information a day later with only
the most cursory of rehearsals. You’ve taken eighteen ”random” objects that were meaningless
and could hence be recalled only through the most arduous of rehearsal processes, converted
them to six “chunks” of three that can be easily tagged by the brain’s existing long term
memory (note that you are not learning the string FBI, you are building an association to the
15Wikipedia: effect.
16Wikipedia: Several items in a row are connected to this page.
17From this you can see why I used ten digits, gave you only a few seconds to look, and blocked rehearsal in our
earlier exercise.

14 Preliminaries
vertebrate animals, with new layers (apparently) added by evolution on top of this core as
the various phyla differentiated, fish, amphibian, reptile, mammal, primate, human. The
outermost layer where most actual thinking occurs (in animals that think) is known as the
cerebral cortex.
• The cerebral cortex9 – especially the outermost layer of it called the neocortex – is where
“higher thought” activities associated with learning and problem solving take place, although
the brain is a very complex instrument with functions spread out over many regions.
• An important brain model is a neural network10 . Computer simulated neural networks provide
us with insight into how the brain can remember past events and process new information.
• The fundamental operational units of the brain’s information processing functionality are called
neurons11 . Neurons receive electrochemical signals from other neurons that are transmitted
through long fibers called axons12 Neurotransmitters13 are the actual chemicals responsible
for the triggered functioning of neurons and hence the neural network in the cortex that spans
the halves of the brain.
• Parts of the cortex are devoted to the senses. These parts often contain a map of sorts of the
world as seen by the associated sense mechanism. For example, there exists a topographic map
in the brain that roughly corresponds to points in the retina, which in turn are stimulated by
an image of the outside world that is projected onto the retina by your eye’s lens in a way we
will learn about later in this course! There is thus a representation of your visual field laid out
inside your brain!
• Similar maps exist for the other senses, although sensations from the right side of your body
are generally processed in a laterally inverted way by the opposite hemisphere of the brain.
What your right eye sees, what your right hand touches, is ultimately transmitted to a sensory
area in your left brain hemisphere and vice versa, and volitional muscle control flows from
these brain halves the other way.
• Neurotransmitters require biological resources to produce and consume bioenergy (provided
as glucose) in their operation. You can exhaust the resources, and saturate the receptors for
the various neurotransmitters on the neurons by overstimulation.
• You can also block neurotransmitters by chemical means, put neurotransmitter analogues into
your system, and alter the chemical trigger potentials of your neurons by taking various drugs,
poisons, or hormones. The biochemistry of your brain is extremely important to its function,
and (unfortunately) is not infrequently a bit “out of whack” for many individuals, resulting
in e.g. attention deficit or mood disorders that can greatly affect one’s ability to easily learn
while leaving one otherwise highly functional.
• Intelligence14 , learning ability, and problem solving capabilities are not fixed; they can vary
(often improving) over your whole lifetime! Your brain is highly plastic and can sometimes
even reprogram itself to full functionality when it is e.g. damaged by a stroke or accident.
On the other hand neither is it infinitely plastic – any given brain has a range of accessible
capabilities and can be improved only to a certain point. However, for people of supposedly
“normal” intelligence and above, it is by no means clear what that point is! Note well that
intelligence is an extremely controversial subject and you should not take things like your own
measured “IQ” too seriously.


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