Transcript Ch04b

Part 2. The Modular Brain
• Module - A self-contained part of a larger system. It
takes a specific bit of input and generates a specific
bit of output.
• Damage to a module will result in the loss of a
specific function (a dissociation)
• If the mind uses RULES, they are probably processed
by modules that can be identified and studied
• A damaged module will result in the loss of a rule
Back to the Future
• Phrenology
Mapping from the Outside
• Franz Josef Gall (1758-1828)
– Used the clinical method to map
the brain and confirm:
• Existence of white and gray matter
• Fibers from each brain side to the
opposite spinal column side
• Fibers connecting the two brain
hemispheres
– “How do the size and shape of
the brain reveal information
about brain facilities?”
– Can it be mapped from the
outside?
– Theory flopped - was it
abandoned too quickly?
Cerebral Hemispheres
Paul Broca (1824-1880)
– The Clinical Method (1861)
– Broca’s area: the speech center in the 3rd
frontal convolution of the left hemisphere
of the cerebral cortex
Anti-Module Data
Ivan Pavlov (1849-1936)
• Shifted from physiology to psychology
with research into psychical reflex
(classical conditioning).
• Variations of classical conditioning:
- US, UR, CS, CR
• Many researchers began to see the brain
as a device that simply linked input and
output (predecessor of Behaviorism)
Physiology of the Nervous System
• Camillo Golgi (1844-1926)
– Italian neurologist
• S. Ramón y Cajal (1852-1934)
– Spanish neuroanatomist
– Nobel Prize 1906
Pavlov and S-R Psychology
• Pavlov’s Findings combined with the study of
neuroanatomy led many to believe the brain was a
large homogeneous network. Hence, Behaviorism.
Not So fast
• It LOOKS modular!
• Brain damage in certain areas leads to
predictable deficits.
Memory and Modules
• Long-Term memory
– What is your name?
– Duration: Decades
• Working memory (Short-term memory)
– What did I just say?
– Duration: If not actively manipulated (rehearsed)
most info is gone in 10 seconds
• Examples of people losing one without losing
the other. Dissociation suggests modules.
Modules within WM
Can we Compromise?
Nyet!
Non!
Part 3. Rules
• Basic IF (antecedent) - THEN (consequent)
statements
• More flexible than standard logic
– Allows alternatives and “best fit” solutions (e.g. penicillin)
– Serves as a general procedure that can accept many types of
input and process them similarly
– Rather than
• Skipped class + Yesterday = Skipped class
– Use
• Any action on object + before today = -ed added to
the end of verb plus object
Rules and Problem Solving
• Each Rule can narrow your choices and make
the next decision easier or alters the outcome
• Heuristics: Rules of thumb that spare us from
the need to search all possibilities
Problem Solving
• Rules can help us reason forward and backward
– Planning: How can I prevent heart disease?
– Explanation: How did I get heart disease?
• Both can be limited and biased by what you
already know.
– A string of rules can be described as a PLAN
– Choosing among competing plans can be
difficult, but exhaustively searching every
possibility would take an eternity
Psychological Plausibility
• Perhaps working memory stores goals and
compares plans?
• Perhaps synapses are modified as we
acquire and update rules?
• Long chains of rules can look like
thinking/intelligence
TIC TAC TOE
•
Priority of rules
1.
2.
3.
4.
5.
6.
7.
IF row of X or row of O THEN - Game over
IF there is a row, column or diagonal with two of my pieces
and a blank space THEN play the blank space - Game over
IF there is a row, column, or diagonal with two of
opponent’s pieces and a blank space, THEN play the blank
space to block - Opponent Play
IF the center is blank THEN play center - Opponent Play
IF there is an empty corner THEN play corner according to
clock rule - Opponent Play
IF empty space THEN play according to clock rule Opponent Play
Game Over
Rules of Language
• Steven Pinker
– Harvard U.
– Language Acquisition and
the evolution of language
• Syntax - Rules of language
– Are they learned? He thinks
not!...mostly.
Rules of Language
• Inflections
– Adding -ed to past tense verbs
– Adding -s to plural nouns
– (Sometimes) adding -ess/er to female/male
nouns
• Are we wired to inflect?
Rules of Language
•
Two schools of thought
1. Associationism
•
•
Similar to behaviorist approach
Present and past tense forms are both
stored and somehow linked
2. Rule-and-representation
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•
We have the verb plus a rule that generates
the past tenses on the fly.
There is no need to store past tense forms
Try These
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Today I will crittle the house.
Yesterday I _______ the house.
Today I will strow the car.
Yesterday I ______ the car.
Today I will bling my outfit.
Yesterday I _____ my outfit.
Try These
• Regular familiar
– Today I will crittle the house.
– Yesterday I _______ the house.
• Irregular unfamiliar
– Today I will strow the car.
– Yesterday I ______ the car.
• Irregular “familiar”
– Today I will bling my outfit.
– Yesterday I _____ my outfit.
Regular and Irregular Verbs
• Regular verbs (lift, walk): add -ed for past tense
– Today I walk
– Yesterday I _______
• Irregular verbs (go, drink, throw)
– Some are truly unique (be-was, go-went), but others
can be grouped
• sing, ring, spring, fling
• grow, blow, throw
– Unfamiliar verbs that fit a subgroup often get
channeled into the regular verb processing system
Regular and Irregular Verbs
• When a verb is intuitively perceived as being
derived from a noun or adjective are processed as
regular
– Fly-out
– Grandstand
• Once the -ed rule has been established, irregular
verbs must be practiced and associations must be
formed to pull them away from the rule (children
and overgeneralization).
Regular and Irregular Verbs
• When people are provided with present tense
verb forms…
• Past tense forms of irregular verbs have been
learned (hard wired) and are generated faster
than the past tense forms of regular verbs which
are processed from scratch each time.
Rule-Associative Memory Hybrid Theory
Link to past tense form activated
Irregular
Verb+ Yesterday
Past Tense Form
Generated
Regular
Regular verb processor
“-ed” added
Evidence - Children
Link to past tense form activated
Irregular
Yesterday +
Sing
Regular
Bang!
I Sing’d-ed
Regular verb
processor
“-ed” added
Evidence - Aphasics
Link to past tense form activated
Irregular
Smile + yesterday
Regular
Regular verb processor
“-ed” added
I “smile”
Evidence - SLI
Link to past tense form activated
Irregular
Smile + yesterday
Regular
Rule system might not
exist!
I “smile”
Williams Syndrome
• Broken arm of chromosome 7
• Remarkable language Skills
despite cognitive difficulties in
many other areas
• Evidence that language is
autonomous of many other aspects
of cognition.
Summary
• Rules offer a means of explaining many
types of cognitive processes
– ACT-R’s approach to addition might be
comparable to human thought process. It has
proven effective in education
• Linguists see syntax as a collection of
rules and there is evidence that, in some
cases, the brain does too.
Next Time
• Rules, Modules, and Connectionism
• More AI and Connectionism
– Connectionist networks…
• are wired like neurons
• can “learn”
– Neurons and groups of neurons (modules) are
interconnected