VI. Learning and Believing I Brain, Mind, and Belief: The Quest
for Truth As thinking beings, we continually try to make sense of
our world. Sounds like a good thing, right? Except that any piece
of information that doesnt quite fit with our beliefs, we alter
without even noticing. We knead and we squeeze until everything
finally fits into the tight box of our limited belief system. Pam
Grout (2013) Slide 2 Learning and Believing (topics for October 21
and 28) Learning: The neurological process Evolution as a
long-range learning process Evolutionary factors leading to
expansion of human cortex The great flexibility of the human
learning potential Cultural evolution Aids to the mind and the law
of consequent decline The results of learning: Knowledge or
beliefs? Sources of information leading to beliefs The great
variety of belief systems in America The construction and
maintenance of beliefs Belief system inertia Self-reinforcement of
the belief system Managing new information: Left-brain and
right-brain factors 2 Slide 3 Functions of cortical columns
Integration: A column is activated if it receives enough activation
from other columns Can be activated to varying degrees Higher
degree of incoming activation results in higher degree of outgoing
activation Can keep activation alive for a period of time
Broadcasting: An activated column transmits activation to other
columns Exitatory Inhibitory (to competitors) Learning: adjustment
of connection strengths and thresholds 3 Slide 4 Learning Links get
stronger when they are successfully used Learning consists of
strengthening them Hebb 1948 Threshold adjustment When a node is
recruited its threshold increases Otherwise, nodes would be too
easily satisfied 4 Slide 5 Results of learning The increased
connection strengths and node adjustments represent newly acquired
information Two types How to skills How to ride a bicycle, play a
piano What knowledge/beliefs To be knowledge it has to represent
truth It has to be in accord with reality 5 Slide 6 Long-Range
Learning: Evolution Darwinian evolution can be seen as a process of
long-range learning It works by trial-and-error Variety is always
present And is continually produced The more able varieties have
survival They have better chance of surviving They have better
chance of reproducing Consequence: Changes in the genome over
multiple generations Case in point: Human evolution 6 Slide 7
Evolutionary and neurological questions The brain of Homo sapiens
is markedly different from those of chimpanzees What caused/allowed
such rapid and extensive growth? Humans and chimps also differ
greatly In behavior Physically How could such profound differences
arise From a small difference in DNA (about 1%)? In a short time of
separation from chimps (6 million years)? Slide 8 Primate skulls
Bradbury J (2005) Molecular Insights into Human Brain Evolution.
PLoS Biol 3(3): e50.doi:10.1371/journal.pbio.0030050 Slide 9 Human
and chimpanzee brains From Wikipedia Slide 10 Human DNA and that of
our closest relatives, the chimpanzees, Approximately 99% identical
But it depends on just what we measure Some say 98% or 96%
http://news.nationalgeographic.com/news/2005/08/0831_05083
1_chimp_genes.html
http://news.nationalgeographic.com/news/2005/08/0831_05083
1_chimp_genes.html Slide 11 Brain size in mammals Mammal brain size
tends to correlate with body size But human brain exceeds
predictions on this basis by 5-7 fold (Schoenemann 2009: 200) Human
brains about 3 times larger than ape brains Moreover, some parts of
human brain are disproportionally even larger And these parts
support language as well as abstract thinking, planning,
imagination, and other higher level intellectual processes Slide 12
Brain sizes (in grams) Cat30 Dog (beagle)72 Rhesus monkey90-97
Orangutan370 Gorilla465-540 Chimpanzee420 Pithecanthropus850-1000
Human1200-1400 Bottle-nose dolphin1500-1600 Elephant4780 Slide 13
Brain sizes adjusted for body weight ActualAdjusted Cat30360 Dog
(beagle)72470 Rhesus monkey90-97850 Orangutan370700
Chimpanzee420680 Human1200-1400 Bottle-nose dolphin1500-1600212
Elephant478078 Slide 14 Brain size correlates Larger brain size
correlates with Longer life spans Larger size of social groups
Larger groups have more complex interaction Requires more
intelligence Social interaction is enhanced by language Larger
brains vis--vis learning Longer life span provides more time for
learning Language requires learning Language contributes to
learning cf. Shoenemann 2009 Slide 15 Intellectual equipment of
humans, compared with chimps Gray matter More territory in parts of
the cortex that support language Upper temporal lobe (incl. BA 37)
Angular gyrus Supramarginal gyrus Prefrontal lobe (incl. Brocas
area) White matter More connectivity in and among the above Slide
16 Mammal cortices SMG AG Wernickes a. BA 37 Primary oral motor
Brocas a. Pre-frontal Slide 17 800 400 200 100 50 25 | | | | | | |
| | ___________________ Homo heidelbergensis
________________________________ Homo neanderthalensis
_____________________________________________ H o m o s a p i e n s
Development of Language within genus Homo Thousands of years ago
(logarithmic scale) 12 dozen words p r i m i t i v e s y n t a x
clear speech production complex grammar Slide 18 Higher-level brain
structure Higher level-cortical areas do not have genetically
determined functions Unlike primary areas Rather, plasticity reigns
They acquire their functions mainly as a result of Proximity
Experience Plasticity Therefore their evolutionary expansion was
likely promoted by a variety of benefits Slide 19 Mammal cortices
SMG AG Wernickes a. BA 37 Primary oral motor Brocas a. Pre-frontal
Slide 20 Proximity and plasticity Higher level cortical areas are
relatively uniform in structure An established finding from
neuroanatomy They are where they are because of their proximity to
areas they are most closely related to Brocas area: close to
primary oral motor cortex Wernickes area: close to primary auditory
cortex In case of damage to the usual area, a neighboring area can
take over Slide 21 Higher cortical structures The beauty of
high-level cortical structure is precisely that it is not
genetically dedicated to some function (like language) (As
described above) the functions of higher-level areas are determined
by proximity and experience Consequence: enormous flexibility the
ability to do any number of things that could not have been
foreseen Playing Chopin on the piano, driving cars, skate-boarding,
half-pipe, space travel (to moon, to space station), programming
computers, building WMD Slide 22 Half-pipe Slide 23 Problem: How to
explain expansion of brain? Why only humans? Higher-level cortical
areas are Undedicated in advance to any function Therefore,
available to take on anything that might come along Things like,
juggling, playing musical instruments, language, architecture They
are therefore very valuable Then why didnt chimps also develop
larger brains? (not to mention other primates, other mammals) Slide
24 Human and chimpanzee brains From Wikipedia Slide 25 The cost of
a large brain Problem: A large brain uses a lot of energy Human
brain is only 2% of the weight of the body, but consumes about 20%
of the total energy in the body at rest more when thinking Average
power consumption of a typical adult is about 100 W ("Body, Physics
of" Macmillan Encyclopedia of Physics. New York: Macmillan, 1996)
The diet of a chimp presumably like that of our common ancestor
doesnt provide enough energy to support a larger brain Slide 26
Chimpanzee food Tremendously varied diet Mainly fruits and plants
Raw plants are hard to digest and require Large complex digesting
system Uses up a lot of energy Several hours of daily chewing They
also consume insects, eggs, and meat, including carrion All of
their food is raw Except what is fed to them by humans Slide 27
Richard Wrangham:Catching Fire (2009) What made us human was
cooking Cooked food is far easier to digest than raw food, with the
consequences that (1) far more energy is available to humans than
to other animals, and (2) much less time is devoted to chewing food
Since brain activity uses a prodigious amount of energy, other
primates with raw, largely vegetarian, diets simply cant produce
enough energy to support larger brains Slide 28 Richard Wrangham
Professor of Anthropology, Harvard University Slide 29 The cost of
digestion Raw food is harder to digest than cooked food Therefore,
requires more complex digestive system Digestion uses a lot of
energy i.e., less efficient than eating cooked food Advantages of
cooking Cooked food produces more energy than raw Less complex
digestion means more energy available for other functions Slide 30
Raw & cooked food vis-a-vis energy Cooked food is easier to eat
Humans have smaller teeth than chimps Also, smaller jaw muscles
Therefore, more can be eaten in less time Cooked food is easier to
digest Humans have much simpler digestive systems Therefore, dont
have to use as much energy for digesting food Consequence: more
energy available to support a larger brain Slide 31 From
Australopithecus to Homo Wrangham convincingly demonstrates that
the transition from Australopithecus to Homo came about after the
practice of eating cooked food was adopted, allowing for
significant expansion of the cerebral cortex This step was preceded
by the step of eating more meat Slide 32 From Australophithecus to
Homo Australopithecus afarensis (Lucy) About 4 to 2 million years
ago (mya) Adopted the practice of eating meat Habilenes
Intermediate between Australopithecus and homo (some call them Homo
habilis) About 2 to 1.5 mya Adopted the practice of cooking food
Homo erectus About 1.5 to 0.4 mya Slide 33 3200 1600 800 400 200
100 50 25 | | | | | | | | | | | | ________ Australopithecus _______
Habilenes ________________ Homo erectus _________________ Homo
heidelbergensis ______________________________ Homo
neanderthalensis _______________________________ Homo sapiens From
Australopithecus to Homo Thousands of years ago (logarithmic scale)
m e a t e a t i n g c o o k i n g Slide 34 3200 1600 800 400 200
100 50 25 | | | | | | | | | | | | ________ Australopithecus _______
Habilenes ________________ Homo erectus _________________ Homo
heidelbergensis ______________________________ Homo
neanderthalensis _______________________________ Homo sapiens From
Australopithecus to Homo Thousands of years ago (logarithmic scale)
m e a t e a t i n g c o o k i n g P r e l a n g u a g e Slide 35
1600 800 400 200 100 50 25 12.5 | | | | | | | | | | | |
__________________ Homo erectus ______________ Homo heidelbergensis
_______________________________ Homo neanderthalensis
_________________________________________ Homo sapiens From Homo
erectus to Homo sapiens Thousands of years ago (logarithmic scale)
c o o k i n g ? a few words ? primitive syntax complex phonology
Slide 36 800 400 200 100 50 25 | | | | | | | | | _________________
Homo heidelbergensis _________________________________________ Homo
neanderthalensis ______________________________________________ H o
m o s a p i e n s Development of Language within genus Homo
Thousands of years ago (logarithmic scale) a few words p r i m i t
i v e s y n t a x clear speech production complex grammar Slide 37
Being Human And that is a large part of what it is to be human
having brains with a huge amount of undedicated power: the capacity
to adopt new skills, to control new activities Prime example: the
development of complex language some 80,000 to 60,000 years ago
Other examples: music, architecture, economic institutions,
transportation systems, electronics Slide 38 Cultural evolution
Advances made in one generation can be passed to the next Takes
place through learning a consequence of our learning potential
Examples: Writing and reading Shoe making Consequence: Easier
functioning Writing: an aid to memory Shoes: make walking easier on
the feet Slide 39 The law of consequent decline A consequence of
cultural evolution Also of any advance made within the lifetime of
a single individual Operates as a result of the use-it-or-lose-it
principle Examples: Writing: an aid to memory Consequent decline:
weaker memory Shoes: make walking easier on the feet Consequent
decline: softer soles Language: an aid to communication Consequent
decline: loss of skill in communicating intuitively Slide 40 T h a
t s i t f o r n o w ! 40
