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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.

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Presentation on theme: "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."— Presentation transcript:

1 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)

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

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

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

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

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

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)?

8 Primate skulls Bradbury J (2005) Molecular Insights into Human Brain Evolution. PLoS Biol 3(3): e50.doi: /journal.pbio

9 Human and chimpanzee brains From Wikipedia

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% 1_chimp_genes.html 1_chimp_genes.html

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

12 Brain sizes (in grams) Cat30 Dog (beagle)72 Rhesus monkey90-97 Orangutan370 Gorilla Chimpanzee420 Pithecanthropus Human Bottle-nose dolphin Elephant4780

13 Brain sizes adjusted for body weight ActualAdjusted Cat30360 Dog (beagle)72470 Rhesus monkey Orangutan Chimpanzee Human Bottle-nose dolphin Elephant478078

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-à-vis learning Longer life span provides more time for learning Language requires learning Language contributes to learning cf. Shoenemann 2009

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

16 Mammal cortices SMG AG Wernickes a. BA 37 Primary oral motor Brocas a. Pre-frontal

17 | | | | | | | | | ___________________ 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) 1–2 dozen words p r i m i t i v e s y n t a x clear speech production complex grammar

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

19 Mammal cortices SMG AG Wernickes a. BA 37 Primary oral motor Brocas a. Pre-frontal

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

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

22 Half-pipe

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)

24 Human and chimpanzee brains From Wikipedia

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

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

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

28 Richard Wrangham Professor of Anthropology, Harvard University

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

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

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

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

33 | | | | | | | | | | | | ________ 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

34 | | | | | | | | | | | | ________ 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

35 | | | | | | | | | | | | __________________ 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

36 | | | | | | | | | _________________ 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

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

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

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

40 T h a t s i t f o r n o w ! 40


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