Glossary of Psych 85 exam 2 material
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- Analyzing speech (processing path)
- Acoustic signal
- Speech sounds are limited to:
- Those that can be easily produced by the human vocal apparatus
Those that can be easily perceived by the human auditory system
- The vocal apparatus
- The vocal tract is like a musical instrument
Air passing through results in speech sounds
Tract changes shape, unlike a violin or piano--mouth and throat configuration
- Articulatory features
- Speech sounds can be described in terms of their articulatory features
Manner of articulation
Where does the air go and where is it constricted?
E.g., stopped versus nasal versus fricative consonant (p/t, m/n, s/f)
Manner of voicing
When do the vocal cords start vibrating?
/ba/ versus /pa/
Place of articulation
Where does the constriction of air occur?
/ba/ versus /da/ versus /ga/
- The smallest segment of sound that results in a linguistically important contrast is known as a phoneme
A phoneme is defined linguistically rather than acoustically
Different languages have different phonemes
English has 39
24 consonants, 15 vowels
Hawaiian has 13
8 consonants, 5 vowels
Georgian has 90
70 consonants, 20 vowels
- Is speech special?
- Many researchers have argued that speech is processed by a specialized mechanism that is separate from non-speech auditory perception
Others argue that speech is processed by the same mechanisms as other sounds
- Investigating speech perception
- The acoustic parameters of speech can be varied continuously using a speech synthesizer
Example: Voice onset time (VOT)
when do the vocal cords start vibrating?
- English VOT production
- VOT < ~ 40 ms => /d/
VOT > ~ 40 ms => /t/
- Categorical perception
- VOT can be manipulated in a continuous manner using a speech synthesizer
However, the person does not hear a continuous change
We cannot hear a mixture of /d/ and /t/
This is known as categorical perception
we only hear the world after it is categorized into speech sounds (recall perceptual magnet demonstration)
- Cross-language differences
- Different languages have different sets of phonemes
Vowels are fairly consistent across languages
Consonants vary quite a bit
e.g., Xhosa uses clicks
Adult speakers are unable to hear phonemes from other languages that do not exist in their own language
- Cross-Language Differences (Japanese)
- Japanese and Chinese do not have /ra/ vs. /la/ distinction
- /ra/ & /la/ mean the same thing
This distinction is very hard to learn in adulthood
- Is categorical perception innate?
- Infants as young as 1 month old exhibit categorical perception of voice onset time
- Categorical perception in infants
- An infant’s interest in a stimulus is indexed by the frequency of sucking responses.
Stimulus repetition reduces sucking rate (habituation)
Perceptible changes in the stimulus lead to renewed sucking
- Development of phoneme perception
- Newborns have the ability to discriminate phonemes from all languages
e.g., Japanese babies discriminate /r/-/l/
Over the first year, they lose the ability to discriminate non-native phonemes
- Evidence against specialized speech module
- Categorical perception occurs for non-speech stimuli as well as speech
Other species exhibit categorical perception of speech sounds
- Theories of speech perception-basis
- We are able to perceive segments in the speech stream
we can hear the separate phonemes in “dad”
But these separate segments don’t exist in the acoustic signal
The acoustic features of each phoneme overlap in the acoustic signal
This is known as “coarticulation”
The way that one phoneme is produced depends upon which phonemes precede and follow it
How are we able to extract phonemes from the smeared out acoustic signal?
- The relation of acoustic and phonetic signals
- Acoustic features are like puzzle pieces
Phonemes are like the objects in the puzzle
- Two theories of speech perception
- The motor theory
Speech perception involves reconstructing the articulatory movements from the acoustic signal
We listen for the effects of the different parts of the vocal tract, like different instruments in an orchestra
Usually associated with the “speech is special” idea
The acoustic invariant theory
There are acoustic features that signal the presence of each individual phoneme
e.g., relation between amount of high and low frequency energy may signal presence of certain consonants
Treats speech like any other kind of soun
- Speech perception in the brain
- The left hemisphere is particularly important for speech perception
Speech is processed more rapidly when presented to the right ear (which goes primarily to the left hemisphere)
Lesions to the left hemisphere are much more likely to cause deficits in speech perception
- Disorders of speech perception
- Two syndromes give us clues regarding the brain basis of speech perception
Pure word deafness
- Pure word deafness
- Loss of ability to discriminate speech sounds
Intact ability to speak, read, write, and discriminate non-speech sounds (such as music)
“Speech is like a great noise all the time… you think you can catch it and it fades away, like foreign folks speaking in the distance. When people speak loudly or quickly, the words just run together” (Klein & Harper, 1956)
- Wernicke’s aphasia
- Also known as fluent aphasia
Impaired comprehension of the meaning of speech
relatively preserved perception of phonemes
Speech is articulated fluently but is nonsensical
“I called my mother on the television and did not understand the door. It was not too breakfast, but they came from far to near. My mother is not too old for me to be young.”
Follows larger left hemisphere lesions to temporal/ parietal junction
- Speech production-path
- Speaker’s intention to speak (idea)
syntax (sentence structure)
morphology (word form)
articulation (muscle movements)
- Speech errors
- Say this repeatedly as quickly as possible:
“She sells sea shells by the sea shore”
What kind of errors do you make?
Rubber Baby Buggy Bumpers
Peter Piper picked a peck of pickled peppers;
A peck of pickled peppers Peter Piper picked;
If Peter Piper picked a peck of pickled peppers,
Where's the peck of pickled peppers Peter Piper picked?
- Studying speech through errors
- We can deduce the basic building blocks of speech production by examining the kinds of errors that speakers make
Errors occur at each level
Syntax (grammar): word substitutions
I wanted to read the envelope to my grandmother
Morphology (word endings): morpheme substitutions
I want to readed the letter to my grandmother
Phonology (sounds): phoneme subsitutions
I wanted to read the gretter to my grandmother
- Syntactic errors
- Errors of word substitution are nearly always of the same syntactic category
the syntactic category rule
“To the great people of Israel..Egypt, excuse me” (Gerald Ford)
“I wanted to read my grandmother to the letter”
These errors suggest that there is a syntactic level of organization
Words are placed into labeled slots in a “syntactic frame”
- Phonological errors
- There are constraints on which kinds of phoneme errors can occur
Consonants replace consonants and vowels replace vowels
the consonant-vowel rule
The slip nearly always follows the phonological rules of the language
Suggests phonological structure similar to syntactic structure
- The modularity of syntax
- Does phonological information affect syntactic (grammar) processing?
No, it does not, since syntactic rules only reflect syntactic information
Spreading activation theory:
Yes, phonology, meaning, and syntax are part of an interactive network, where each influences the other
- The modularity of syntax-problems
- The modularity theory can explain phonological errors (like “prevent” replacing “present”)
Proposes a later stage of processing, after words have been placed in the syntactic frame
However, it cannot explain “mixed” errors
combinations of semantic and phonological errors
e.g., “stop” for “start”
These are quite common
- Neural basis of speech production
- Damage to the left prefrontal cortex leads to nonfluent (Broca’s) aphasia
Two major features
omission of function words and affixes, relative retention of content words
“Yes ... ah ... Monday ... er Dad and Peter H ... (his own name), and Dad ... er hospital ... and ah ... Wednesday ... Wednesday nine o'clock ... and oh ... Thursday ... ten o'clock, ah doctors ... two ... an' doctors ... and er ... teeth ... yah”
Apraxia of speech
Difficulty in producing the desired speech sounds
Not due to muscle weakness
- A gene for speech?
- The KE family suffers from an inherited speech disorder
about half of the individuals are affected
They have a wide range of problems with language
Making appropriate mouth movements
Comprehending complex sentences
Deciding whether a word is real or not
This is caused by a single-nucleotide mutation in the FOXP2 gene on chromosome 7
The widespread nature of the language problems in the KE family argue against strong modularity
- Preparing to Produce Speech
- In the first months of life, infants’ vocal tracts prepare for speech through crying, sneezing, sighing, burping, and lip-smacking.
At 6 to 8 weeks, infants begin to produce simple speech sounds, like “goo,” “aahh,” and “ooohh.”
- Stages of Speech Production
Begins at about 7 months. Consists of producing syllables made up of a consonant followed by a vowel (“ba,” “pa,” “ma”).
Deaf infants exposed to American Sign Language begin to babble manually, making repetitive hand movements that are components of ASL signs.
- Using Words
- Infants first recognize words; then they begin to comprehend them.
Infants as young as 4 months recognize their own name.
By 7 to 8 months, infants recognize new words and remember them for weeks.
By about 6 months, infants address the problem of reference, associating words with meaning (as shown by looking toward mother or father when someone says “Mommy” or “Daddy”).
- Early Word Production
- Comprehension vocabulary: Words that infants understand.
10-month-old infants comprehend, but cannot say, 11 to 154 words.
Productive vocabulary: Words that infants can say or sign.
Infants produce their first words between the ages of 10 and 25 months.
Early word production is limited to the sounds infants can pronounce.
- Producing Words
- Holophrasic period: The period in which a whole phrase is expressed by a single word. For instance, “drink” can refer to a desire for juice, as could “juice.”
Overextension of meaning: Using a given word broadly, such as “doggie” for any four-legged creature.
- Examples of Young Children’s Overextension of Meaning
- Ball: ball, balloon, marble, apple, egg, spherical water tank (Rescorla, 1980)
Cat: cat, cat’s usual location on top of TV when absent (Rescorla, 1980)
Moon: moon, half-moon-shaped lemon slice, circular chrome dial on dishwasher,
half a Cheerio, hangnail (Bowerman, 1978)
Snow: snow, white flannel bed pad, white puddle of milk on floor (Bowerman, 1978)
Baby: own reflection in mirror, framed photograph of self, framed photograph of others
- Word Learning
- Children use an adult’s focus of attention as a cue to word meaning.
Children draw inferences about a word’s meaning from what is being done as the word is used
- First Sentences
- Children 13 to 15 months old understand that words used in combination have a meaning separate from the meaning of the individual words.
By the end of the second year, children combine words into simple sentences.
Children's first sentences are telegraphic speech, usually two-word utterances in which nonessential elements are missing.
Children rapidly develop the use of sentences containing more words.
- Why is language development interesting? (reasoning)
- Inductive problem - Potentially wide range of hypotheses (e.g. Quine)
[Picture of usagi in ha]
What’s a Gavagai?
-Isolate the meaning using experience and known words
- Mapping problem
- Mapping problem – Cross-linguistic variations in how words map to concepts - Language may organize concepts in different ways
Melissa Bowerman - Differences between English and Korean (differences in use of "put on," "put in," etc.
- Yucatec & English
-Objects described by shapes
-e.g., cups, stapler, ball, etc. regardless of composition
Describe object by material makeup
-e.g., candles as wax
- Why is language development interesting? (growth)
- High growth rate
Word learning begins extremely slowly but accelerates quickly
10,000 words by 1st grade
5.5 per day from 1.5 to 6 yrs
40,000 words by 5th grade
20.5 per day from 1st to 5th grade
- Why is language development interesting? (behaviorism)
- Language is generative
- Current Theoretical Issues in Language Development
- There is virtually universal agreement that children develop language as a results of the interaction between the brain and language exposure—nature and nurture.
There is disagreement with respect to the relative roles of nature and nurture. The three views:
- Nativist Views of Language Development
- The nativist view is led by Noam Chomsky
The “modularity hypothesis” proposes that the brain contains a self-contained language module (LAD) containing a “universal grammar”
In the nativist view, there are brain areas specific to language development (Steven Pinker).
*LAD=Language acquisition device
- Principles and Constraints of Nativist viewpoint
- The Whole Object Assumption
- Language and the Human Brain
- Language is a species-specific behavior.
Only humans acquire language in the normal course of development, although some primates have been taught to sign and recognize words.
Language seems to be localized in the brain.
For 90% of right-handed people, language is primarily controlled in the left hemisphere of the cerebral cortex.
- Support for Nativist Perspective
- Creole languages, e.g. Hawaiian Creole English
-Pigeon language: children grow up hearing pigeon and create creole-> systematic, even though not hearing systematic speech
Language is uniquely human?
Language areas in the brain
- Critical Period for Language Development
- There seems to be a critical period (between the ages of 5 and puberty) during which language develops readily and after which language acquisition is more difficult and less successful.
The extraordinary cases of Victor, the Wild Child of Aveyron (France, 1800), and Genie (United States, 1970) seem to support the critical period hypothesis.
Other evidence for critical period comes from:
Studying the effects of damage to language areas in the brain (children recover more readily than adults).
Studying the ages at which a second language is acquired.
- Hemispheric differences in language processing (Bilinguals)
- The later the age of 2nd language acquisition the greater use of the right hemisphere for language processing
- Test of
- Scores drop off when compared to 1st language for 2nd languages learned after age 7
- Limitations of Nativist Perspective
- Failure to identify what the universal grammar is
Nativist description does not fit observations of language development
Doesn't explain a lot of problems
Language areas in the brain can be damaged and children learn language
- Interactionist Views
- According to interactionist views, virtually everything about language development is influenced by its communicative function.
Language is seen as primarily a social skill (Michael Tomasello).
The structural properties that nativists hold to be innate are mastered in the process of learning to communicate with others.
- Language and the Human Environment
- Having a human brain is not sufficient for language to develop.
Language requires exposure to other people and using language with them.
Caregivers and siblings begin to communicate through language with infants almost from birth.
- Infant-Directed Speech (IDS)
- IDS: A distinctive mode of speech used by adults in talking to infants and young children, even while recognizing that they cannot talk back.
The tone and pitch of IDS seem to be consistent across cultures, including the use of warm and melodious tones for happy and approving messages and short, sharp sounds for expressing disapproval.
- Early Interaction in language development
- The social context promotes language development.
Communication competence is facilitated by infant–parent interactive games.
These interactions are characterized by:
Intersubjectivity: Parent and infant share a common focus of attention.
Joint attention: The parent follows the baby’s head and comments on what the baby is doing or looking at.
IMPORTANT: Only humans look at what a finger is directed to rather than the finger itself.
- Limitations of Interactionist Perspective
- Little account of how children learn grammar (which may be more complex than learning words)
- Connectionists hold that the information needed to acquire language is contained in language and environment (this view is not necessarily in opposition to interactionist views)
Language development is not based on innate linguistic knowledge or special language-specific brain mechanisms but on general-purpose learning mechanisms.
Language development occurs as the result of the gradual strengthening of connections in the neural network.(things that matter are strengthened)
- First/Second Order generalizations
Forks are fork shaped
Balls are ball shaped
Object labels refer to shape of objects
-Don't need to learn each one separately
-Learn that shapes of objects matter
- Limitations of the Connectionist Perspective
- Only a few aspects of language have yet been modeled
What features get built into the model
How well does the input used to “train” the model match children’s input.(their perception)
- What is a category?
- Categories are ways of grouping objects in the world according to their similarity
e.g., dogs & cats
- Why do we categorize
- Categorization lets us make inductive inferences about the world (mean dog=bite)
Inductive inference: reaching a general conclusion based on specific examples (no guarantee of truth)
Lets us make assumptions about features that we don’t necessarily observe
At the same time, categorization is itself an inductive inference
We infer which category the object goes in depending upon its features
- Gelman & Markman experiment
- Shown flamingo
“See this bird, it feeds its babies mashed-up food”
“See this bat, it feeds its babies milk”
“What does this bird feed its babies?
- Inductive inference from categories(Gelman & Markman results)
- 85% of preschoolers guessed that the blackbird feeds its babies mashed-up food
They used category information, rather than perceptual similarity, to make their inference
A control group of children guessed this only 50% of the time
This group was not told about the bats and flamingos beforehand.
- What is a theory of categorization?
- Describes two things:
How are categories represented in memory?
What is stored in memory?
- Similarity and representation
- Most theories of categorization say that we categorize novel items based on their similarity to familiar things
Items must thus be represented in a way that allows us to determine their similarity
Two ways to do this:
Dimensional (geometric) representation
Feature list representation
- Dimensional (geometric) representation
- each entity is represented as a point in a multidimensional space
-attributes pull the focus of all attributes based on their strength and location in 3D space
- Metric spaces
- The dimensions in psychological space are metric
Like those of physical space
Similarity is determined by Euclidean distances between points in the metric space
Metric space follows several axioms
Symmetry: d(a,b) = d(b,a)
Triangle inequality: d(a,b) + d(b,c) ≥ d(a,c)
- Tversky’s criticism of dimensional model
- If similarity is related to distance between exemplars in metric space, then it should obey the axioms of a metric space
distance(A,B) = distance(B,A)
distance(A,C) ≤ distance(A,B) + distance(B,C)
- Violations of metric space axioms
Identical twins are judged as more similar than two squares
How similar is North Korea to China?
How similar is China to North Korea?
How similar is Jamaica to Cuba?
How similar is Cuba to the Soviet Union?
How similar is Jamaica to the Soviet Union?
Similarity judgments do not observe triangle inequality
d(J,SU) >> d(J,C) + d(C,SU)
- Featural representation
- Each item is represented as a list of features
Apple: round, hard, red, has-stem, is-edible
Similarity between items is determined by the overlap of features
Tversky’s contrast model
S(A,B) = a*f(A B) - b*f(A - B) - c*f(B - A)
This model can account for the violations of metric space axioms shown by Tversky
- Where do categories come from?
- The rationalist answer:
We are born with them
The empiricist answer:
We learn them
A middle road
We learn categories, but the kinds of categories that we learn are constrained
- How are categories stored in memory?
- Three theories
- Classical theory
- A category is defined in terms of necessary and sufficient features
Necessary: has to be there
Sufficient: all that you need
These features define the category
This representation is abstract
It does not store any information about specific exemplars
- What is a square? (classical theory of categorization)
- A square is defined by the following features:
sides equal in length
- Criticisms of the classical theory
- Defining features often can’t be found
You can often remove any particular feature and some object will still be a category member
Non-necessary features affect categorization
- What is a “game”?(crit. of clas. the. of cat.)
- Wittgenstein’s (1953) critique
What is the necessary feature of the concept of a game?
competition between people or groups?
has a winner?
provides amusement or diversion
are professional athletes amused or diverted?
For many categories there are no clear defining features
Various members share various features, but there is no single feature that is necessary
- Typicality effects
- How long does it take to verify the following?
A robin is a bird
An ostrich is a bird
A bluejay is a bird
A penguin is a bird
Some members of a category are more “typical” than others
They are verified more quickly
But, these differences are related to non-necessary features, which are not included in the classical theory
- Probabilistic theories
- Failure of classical theory led to proposal that category representation may be probabilistic rather than deterministic (rule-based)
Both are based on the idea of similarity
- Prototype theory
- Categories are represented by the average of all members of the category
e.g., the concept “bird” is represented by a prototype that is very similar to a robin and different from an ostrich
The prototype need not exist in the real world
The category representation is abstract
does not store information about specific exemplars
- Posner & Keele (1968)
- Subjects presented with dot patterns created from two prototypes
Categories 1 and 2
They are later asked to classify new dot patterns into either category 1 or 2
- Dot Pattern Classification
- Posner & Keele found that subjects were more likely to endorse the prototype as a category member than they were for a new distortion
Even though they never saw either the prototype or the distortion
Suggests that subjects store an “average” of their experiences
- Problems with prototype theory
- Assumes that information about individual instances is not stored
However, people do seem to store information about individual exemplars
- Correlated features
- Imagine a new player who is 6’2” and 150 pounds
Which team would he/she most likely be on?
Prototype theory can’t decide, since he/she is equally similar to the average of both groups
There is evidence that people can use
information about correlated features
- The exemplar theory
- Concepts are represented by all of the exemplars that have been experienced
The category “bird” is represented by memories of all previous experiences of birds
When we categorize something, we compare it to all of the exemplars in memory, and decide the category based on the most similar exemplars
The category representation is concrete
There is not necessarily a summary of the category
- Problems with both prototype and exemplar views
- Both rely heavily on the idea of similarity
- Problems with similarity
- Take a blackbird, remove all of its feathers and clothe it in a suit of bat skin
Is it more similar to a bat or a blackbird?
Would you categorize it as a bat or a blackbird?
Similarity is always relative
There are an infinite number of ways in which two things can be similar
We require some way of knowing what features are being compared
- Theory-based categorization
- We know much more about categories than a list of their features or their values in dimensional space
Categories provide explanations for how things work in the world
The same way that theories provide explanations for scientific phenomena
They center on causal relations between entities in the world
Theories guide perception by leading us to believe that particular features are interesting and others are not
- Goal-derived categories
- People can easily construct new categories
“Things to bring on a picnic in the mountains”
Category members are not necessarily similar
These categories behave much like standard categories
e.g., they show typicality effects
Suggests that categorization is driven by goals and theories
- The neural basis of categorization
- The basal ganglia are necessary for learning new categories
Neurons in the frontal lobe fire in response to categorization decisions
Damage to the temporal lobe can result in loss of knowledge about particular categories
- The basal ganglia
- The basal ganglia are a set of deep brain structures
Patients with disorders of the basal ganglia have trouble learning some kinds of categories
Particularly in learning by trial-and-error
Recordings in monkeys show that neurons in the basal ganglia fire when particular features are present and those features are associated with rewards
- Weather prediction task
- Predicting weather from four designs presented on cards
-feedback not reliable
Subjects say what gives the optimal success rate pretty well.
Amnesic subjects do well during task, but have little recall of task afterwards
Parkinson's subjects (basal ganglia damage) perform poorly on the task, but have normal recall.
- Freedman et al. (2002)
- The frontal lobes and categorization
delayed match-to-sample task
-artificial stimuli was more or less catish/dogish
Frontal neurons fire differently depending upon
the particular category
- The temporal lobe and categorization
- Damage to different parts of the temporal lobe can result in loss of knowledge about objects from specific categories
-subject lost knowledge about living things
--could be a separate area for living or aspects common to living things
- Kinds of reasoning
- Deductive reasoning
-Conclusions follow directly from premises using rules of logic
-Guaranteed to be correct(assuming the premises are correct)
-Probable guesses made on the basis of prior evidence
-Not guaranteed to be correct
- Deductive reasoning
- Statements of the form:
if a, then b
Two valid forms of deduction:
if a, then b; a, therefore b
if a, then b; not b; therefore, not a
Two invalid forms of deduction:
denial of the antecendent
if a, then b; not a; therefore, not b
affirming the consequent
if a, then b; b; therefore, a
People can easily understand and follow these rules
- Can deduction fail?
- The Wason selection task
each card has a number on one side and a letter on the other
If there is an A on one side of the card, then there is a 3 on the other side
Which cards could you turn over that could disconfirm this rule?
A 3 D 7
- The selection task
- To test:
if A, then 3
One should look at:
A (if the other side is not 3, then it violates modus ponens)
7 (if the other side is A, then it violates modus tollens)
Subjects don’t do this
They rarely choose the 7 card, which could falsify the rule
They often choose 3, which cannot falsify the rule
People can reason deductively in principle, but are not always so good in practice
- The Wason task in social life
- Another proposed rule (social contract):
If someone drinks beer, then he/she is 21 or over
Each card has age on one side and drink on the other
Which would you turn over to test this rule?
- The selection task and evolutionary psychology
- Cosmides has argued that people are good at reasoning in particular situations that have been present in evolution
Evolution has selected for the ability to reason in social situations, such as detecting cheaters
It has not selected for the ability to solve abstract logic problems
This issue is highly controversial!
- In many cases we cannot rely upon deductive inferences
Instead we rely upon induction
Induction does not guarantee a correct answer!
However, some inferences are more likely to be right than others
Remember inverse optics
- Example of induction
- We would like to form universal generalizations about the world
All X’s are Y
e.g., All swans are white
These are based on our previous experience
Swan #1 was white
Swan #3265 was white
therefore, all swans are white
- The problem with induction
- Induction is only guaranteed if we have experienced all possible instances
e.g., there are black swans in Australia
- Probabilities and induction
- Since induction is not guaranteed, we have to choose the inductive inferences that are most likely to be correct
Probability theory is the science of likelihoods
Do humans behave according to probability theory?
- Why do humans not behave according to probability theory?
- We can’t gather the necessary data
You eat a mushroom and several hours later you get very sick
You make the inductive inference:
Eating the mushroom caused my sickness
No scientist would accept this inference
It’s based on too little data!
the sickness could have been caused by an infinity of other causes
But, none of us (even the scientist) is going to eat the mushroom 100 times to determine the probability of sickness
- The biology of induction
- Induction is built into our brains by evolution
We have built-in biases towards certain kinds of inductive inferences and against others
- Garcia et al. (1972) experiment
- Rats placed in four conditions
When the rat drinks from a bottle:
bottle clicks and rat gets shock
bottle clicks and rat gets radiation (which makes it sick later)
rat gets sweet water and gets shock
rat gets sweet water and radiation
What does the rat learn?
- Induction in rats
- Rats are not able to associate events arbitrarily
They associate sickness with sweetness, not click
The associate shock with click, not sweetness
Biology has built biases into the rat’s learning system
Sickness is more often associated with taste than with sound
- Judging probabilities
- In order to make many kinds of judgments, it is necessary for people to make judgments about the probability of given events
What is the probability that you will get an A if you don’t study?
What is the probability that you will win the lottery?
Probability theory shows us how this is done
- Introducing Bayes’ theorem
- Let’s examine the bomb-sniffing machines at the airport
The test has a high sensitivity
P(positive test | bomb) = 1
The test also has a relatively high specificity
P(negative test | no bomb) = 0.9999
What is the probability that I have the bomb given a positive test result?
Bayes’s theorem gives us this
however, we must know P(bomb) and P(positive test)
these are known as the base rates
- Bayes’ theorem: example
- (B) = 1/1,000,100 = .000001
P(T) = 101 / 1,000,000 = .000101
P(T | B) = 1/1 = 1
P(B | T) = --------------- = 0.0099
- Biases in human judgment
- In many cases, humans do not judge probabilities according to the rules of probability theory
Instead, they use heuristics
- Representativeness heuristic
- “Steve is very shy and withdrawn, invariably helpful, but with little interest in people, or in the world of reality. A meek and tidy soul, he has a need for order and structure and a passion for detail”
What is the most likely occupation for Steve?
People judge probabilities based on the degree that the situation is similar to, or representative of, their stereotypes or knowledge
They do this even when there is other information that a rational person would use to make the best possible decision
- Base-rate neglect
- Kahneman & Tversky (1973)
Showed subjects personality descriptions allegedly sampled at random from a group of 100 professionals (lawyers & engineers)
There are 70 lawyers and 30 engineers
Without seeing a personality description, subjects accurately judge the probability of any one being a lawyer as 70%
Given a description that is representative of one or the other profession, subjects completely ignore base rates
What about non-informative description?
Dick is a 30 year old man. He is married with no children. A man of high ability and high motivation, he promises to be quite successful in his field. He is well liked by his colleagues.
Subjects judge 50% likelihood of each, ignoring base rate!
- Misconceptions of chance
- People expect that a sequence of events generated by a random process will be representative of a longer random sequence
In flipping a coin, people think H-T-H-T-T-H is more likely than H-H-H-T-T-T (which seems nonrandom) or H-H-H-H-H-T (which seems like an unfair coin)
The Gambler’s Fallacy
After a long run of red on the roulette wheel, people think that black is now “due to happen”
Chance is viewed as a self-correcting process
- Hot streaks?
- Most people believe in “hot streaks” for basketball shooting
Gilovich et al. (1985) found that 91% of fans thought that a player has a greater chance of making a shot if they have made the previous 2 or 3 shots
Gilovich et al. examined shooting performance for a professional basketball team over an entire season
The found that the hot streak is a fallacy
The chance of hitting a shot does not depend upon whether the player has made the previous shot
People tend to underestimate the probability of streaks occurring by chance
- Availability heuristic
- The judged probability of an event is related to how easily that event can be brought to mind
Have school shootings become more or less prevalent in the last 10 years?
This is a useful cue, but not a fully accurate way to judge probability
- Demonstration of availability
- Is it more likely that a word starts with r or has r in the third letter?
How do you decide?
Search your memory for words beginning with r, or words with r in the third place
It’s much easier to search for r at the beginning
Most people judge it to be more likely in the beginning (Tversky & Kahneman, 1973)
-even for consonants like r or k that are actually more likely in the third position
- Decision making
- You are ready to buy a new car. How do you decide which one to buy?
How much money do you have?
Which car will last the best?
Which car will you most enjoy driving?
Most decisions are made under some level of uncertainty
What kind of risks are you willing to take, and what aspects of the decision are most important to you?
- Rational decision making
- The goal of decision making is to get the most/best stuff as often as possible
This involves two kinds of information
How important is each outcome?
How likely is each outcome?
The product of utility and probability is known as expected utility
This is what the rational decision maker wants to maximize
- Expected utility
- Expected value is determined by probability multiplied by value
e.g., If you are playing roulette and there is a 1/20 chance of winning $100, the expected value of the gamble is $5
Our preferences for particular outcomes do not map directly onto their expected value
We describe our preferences in terms of expected utility
How much is each possible outcome worth to us?
How does expected utility relate to expected value?
- Risk aversion for gains
- Would you choose:
a certain $100
a 50/50 chance to win $200 or nothing
Most subjects will choose the certain $100
People are “risk-averse” when it comes to gains
Where “risk” is defined as a chance with a known probability
Utility function is concave for positive gains
- Risk seeking for losses
- Would you choose:
a certain loss of $50
a 50/50 chance of a $100 loss or no loss
Most people will choose the latter
People are “risk-seeking” for losses
Utility function is convex for negative gains and is steeper than the gain function
A particular loss looms larger than the same size gain
- A complication: The fourfold pattern of risk attitudes
- The degree to which people are risk-seeking or risk-averse depends upon the likelihood of the event
- Framing effects
- Problem 1:
Assume yourself richer by $300 than you are today. Would you choose:
a sure gain of $100 (72%)
a 50% chance to gain $200 and 50% change to gain nothing (28%)
300/500 -viewed as a gain
Assume yourself richer by $500 than you are today. Would you choose:
a sure loss of $100 (36%)
a 50% chance to lose nothing and 50% change to lose $200 (64%)
300/500 -viewed as a loss
In each case the expected value is $400.
People tend to interpret a choice in terms of the given frame of reference
This combines with the asymmetry of the utility function to cause behavior that differs depending on the description
- The neural basis of decision making
- The prefrontal cortex is necessary for decision making
The case of Phineas Gage
The gambling task
Decision making relies upon emotional processes
- The tale of Phineas Gage
- From the Ludlow, VT Free Soil Union, 9/14/1848
Horrible accident - As Phineas P. Gage, a foreman on the railroad in Cavendish (Vermont), was yesterday engaged in tamkin for a blast, the powder exploded, carrying an iron instrument through his head an inch and a fourth in circumference, and three feet and eight inches in length, which he was using at the time. The iron entered on the side of his face, shattering the upper jaw, and passing back of the left eye, and out at the top of the head. The most singular circumstance connected with this melancholy affair is, that he was alive at two o’clock this afternoon, and in full possession of his reason, and free from pain.
- Changes after the Phineas Gage accident
- Prior to his injury, Gage was described as:
“One of the most efficient and capable foremen” employed by the contractor
“a shrewd, smart businessman”
“energetic and persistent in carrying out his plans”
After the injury (Harlow):
“The equilibrium or balance…between his intellectual faculties and his animal propensities seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned in turn for others more appealing. …In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was ‘no longer Gage’.”
Gage died 11 1/2 years after the accident
- Gage’s brain
- Damasio et al. (1994)
Reconstructed the area of damage in Gage’s brain based on his skull and other information
The area of most likely damage was the ventromedial frontal cortex
- Gambling task results
- Normal subjects:
start off sampling all decks
begin choosing high-payoff, high-risk cards for a little while
then, they move to preferring low-payoff, low risk cards
Ventromedial frontal lesion patients:
Start off sampling from all decks
Then, they choose almost exclusively from the high-payoff, high-risk decks
even though these are not optimal!
- Emotion and decision making
- The trolley dilemma (Greene et al., 2001)
A trolley is approaching 5 people who are tied to the tracks.
There is a switch that can cause the trolley to change to a different track, where only 1 person is tied. Would you flip the switch?
A train is approaching 5 people tied on the tracks. You are on a bridge over the tracks. If you push one person off the bridge onto the tracks, the train will stop before it hits the 5 people. Would you push the person off the bridge?
- What are the two primary functions of working memory?
- There are two primary functions of working memory:
holding information immediately in mind
Performing operations on the maintained information
- Working Memory Tests
- Thinking and memory
- Thinking involves interaction between two types of memory
Maintains and manipulates information relevant to the current goals
Holds the stored record of prior experience
- Mental arithmetic
- How is memory involved in doing mental arithmetic?
rules of arithmetic
learned strategies for solving problems
Holds information about the particular problem
Applies the rules and strategies retrieved from long-term memory to the present information
- Are working and long-term memory distinct?
- Studies of patients demonstrate a double dissociation
Patients with anterograde amnesia have normal working memory but impaired long-term memory
e.g., patient H. M. (more on this next lecture)
Some patients have impairments of working memory
patient K. F.
K.F. has a digit span of 1 item
However, his long-term memory is normal
- Serial position curves
- Subject is given a list of items to remember, one at a time, followed immediately by a memory test
Some items are better remembered than others
Primacy effect: beginning of list is better remembered
Recency effect: end of list is better remembered
- Interpreting serial position effects
- Primacy effect is due to long-term memory
Early items get more practice so they are more likely to end up long-term memory
Recency effects are due to working memory
Subjects hold the last few items in working memory once the study period ends
Amnesic patients have normal recency effect but no primacy effect
Patients with working memory deficits show the opposite pattern
- Baddeley’s model of working memory
- Storage (maintenance) components:
Processing (manipulation) component:
- The phonological loop
- The phonological loop maintains linguistic information in a phonological form
example: rehearsing a phone number
stores a limited amount of information for a limited time
recirculates the contents of the store
- Capacity of the phonological store
- Capacity of the store can be measured using the digit span task
The average is 7 +/- 2
7 +/- 2 whats?
Defined in terms of chunks
Learned units that are treated as a single item
- Patient PV
- Presented following a stroke
Damage to temporal and frontal regions
Unable to “understand” even short sequences of spoken digits
Unable to perform mental arithmetic
Severely impaired short-term memory
Digit span: 4
Letter span: 1.8
Word span: 2.8
- Patient PV: single consonant Brown/Peterson paradigm
- Get item that subject is asked to recall then perform distractor task (e.g., counting backwards by 3s) while trying to hold information in mind
Visual 100% after various delays
Auditory performance descends quickly to chance by the 3 sec delay trials (buffer already cleared)
- The Visuospatial buffer
- Stores visual/spatial information
Supports mental imagery
e.g., imagine your first-grade classroom
- Separating the visuospatial buffer and phonological store
- Brooks (1968) study
Visual task: Subjects mentally navigated the edges of a block letter, noting at each vertex whether it was at the top or bottom versus middle of the figure
Verbal task: Subjects given a sentence, noting for each word whether it was a noun or not
Responded by saying “yes/no” or pointing to “yes/no” haphazardly arranged on a sheet of paper
Double dissociation between visual and verbal working memory
verbal task=higher performance with point to response
visual task=higher performance with say response
- Patient E.L.D. (Hanley et al., 1991)
- Suffered stroke to right fronto-temporal region
Reported difficulties in finding her way home, and memory problems for unfamiliar material
Severe deficit in visuospatial memory
Normal auditory short-term memory
- Corsi blocks (spatial span) task
- similar to digit span but uses locations of blocks
- Double dissociation within STM
- Patient P.V.
- suggests that STM is not a unitary function
- The central executive
- A set of processes involved in the processing of information from the phonological and visuospatial stores
Keeping track of goals at various levels
Choosing which aspects of a particular piece of information to work with
Deciding the order in which to perform a set of operations
- The neural basis of working memory
- In humans, different aspects of working memory are associated with different brain regions
In primates, single neurons seem to hold information in memory
- Maintenance in the brain
- Phonological rehearsal tasks are associated with activity in:
left frontal lobe
left parietal lobe
Visual/spatial maintenance is associated with activity in:
right frontal lobe
right parietal cortex
Patients with working-memory deficits (such as K. F.) usually have damage to the parietal lobe
- Maintenance in single neurons
- Goldman-Rakic and colleagues have shown activity in single neurons related to visual/spatial maintenance
- working memory in monkeys:
oculomotor delayed response task
- Lesioned prefrontal cortex monkeys have far more errors than controls.
error rates rise quickly with delay length (90% error at 6 sec delay)
- Funahashi et al.:
- Monkey had to remember a particular position over a delay
Individual neurons in the prefrontal cortex fire during the delay for particular locations
- The central executive in the brain
- Damage to the prefrontal cortex leads to deficits in executive processes
Wisconsin card sorting task
- Wisconsin card sorting task
- Subject is given cards with shapes that vary on three dimensions
color, shape, and number of shapes
Subject sorts cards into two piles
Experiment provides feedback after each response
Rules change so subject must adapt
Rule is deterministic
- Prefrontal cortex and the central executive
- Patients with prefrontal cortex lesions are impaired at the WCST
The exhibit perseveration (can't leave first rule)
They keep responding based on a previous rule despite evidence against this rule
May continue for as many as 100 trials!
-know it is not right but cannot change; cannot make use of knowledge
- Duncker’s (1945) radiation problem
- Suppose you are a doctor faced with a patient who has a malignant tumor in his stomach. To operate on the patient is impossible, but unless the tumor is destroyed, the patient will die. A kind of ray, at a sufficiently high intensity, can destroy the tumor. Unfortunately, at this intensity the healthy tissue that the rays pass through on the way to the tumor will also be destroyed. At lower intensities the rays are harmless to healthy tissue but will not affect the tumor either. How can the rays be used to destroy the tumor without injuring the healthy tissue?
- What is a problem?
- A problem has 4 components
What do we need to accomplish?
What do we know from the start?
Means of transformation
How can the initial state be modified?
What stands in the way between the initial state and the goal?
- Solving well-defined problems
- In a well-defined problem:
the goal is known
the givens are known
the means of transformation are known
The obstacle to solving the problem is usually that there are too many possible solutions for us to entertain all of them
- A general theory of problem solving
- Newell & Simon (1982)
Problem solving is described in terms of:
Initial state - where problem solving begins
Goal state - the solution of the problem
Operators - a set of actions that can alter the current state
Path constraints - constraints on the solution beyond reaching the goal state (e.g., solving in the fewest possible steps)
- Problem solving as search
- The problem space is the set of all states that can be potentially reached from the initial state using the available operators
The activity of problem solving is then viewed as a search through this problem space
the problem solver must find a path from the initial state to the goal state using the available operators in accordance with the path constraints
- Narrowing the search
The size of the problem space increases exponentially with the depth (number of steps) of the search
Suppose a game of chess lasted 60 moves, with an average of 30 alternative legal moves at each step
This would give 30^60 alternatives
A computer processing 1 billion moves per second would take 1.3 X 1072 years to search through all of these for the best one!
The Universe is only ~1.5 x 1010 years old
How do we narrow the search?
- Heuristic search
- Instead of searching all possible states, humans focus on searching a small subset of possible states
Humans will often “satisfice”
Find a “good-enough” solution rather than the best possible solution
- Means-ends analysis
- Involves a mixture of forward and backward search
Steps of means-ends analysis:
1. Compare the current state and goal state and identify differences between the two. If no difference, then stop (problem is solved), otherwise, go to step 2.
2. Select an operator that would reduce one of the differences between the current and goal state
3. If possible, apply the operator; if not, set a new subgoal of reaching a state at which the operator can be applied. Then, apply means-ends analysis to this new subgoal.
4. Return to step 1
This is also known as recursive subgoaling
- Example of means-ends analysis
- How should you get from UCLA to the Empire State Building?
Fly from LA to New York
Takes care of the biggest difference.
That creates new sub-problems
Getting from UCLA to the airport
Getting from a New York airport to the Empire State Building
Each of these new sub-problems needs to be solved.
- Problem solving in the brain
- The prefrontal cortex is involved in problem solving
Tower of London/hanoi task
Patients with frontal lobe lesions are impaired at solving the problem
The frontal lobe is active when normal subjects solve the Tower of London
- Memory systems
- Most researchers now agree that there are multiple memory systems in the brain
e.g., declarative memory: Conscious memory for previous events and facts
- How is memory tested?
- Subjects study a list of items
Two types of memory tests
please tell me all of the items from the list that you saw before
did you see this item before: yes/no
- Recollection vs. familiarity
- There are two kinds of long-term declarative memory
Consciously remembering the past
Vivid sensation of re-living the event
Both recall and recognition tests can rely upon this
A sense that something is familiar, without recollection of the prior event
The “Butcher on the street” phenomenon
Recognition tests can rely upon this
- Stages of long-term memory
Placing information into memory
Keeping the information in a permanent store
Bringing information back from storage
- Principles of encoding and retrieval
- Levels of processing
- Levels of processing
- Memory depends upon the depth of processing
processing of surface aspects such as sound or visual features
processing of meaning
Recall is better following deep processing
This is regardless of the subject’s intention to remember!
- Hyde & Jenkins (1968)
- Subjects performed one of four tasks with a list of 24 words
1) Intentionally commit words to memory
2) Judge pleasantness of words
3) Judge whether there is an “e” in the word
4) Judge how many letters are in the word
-Memory was better after
deep versus shallow encoding
-Intentional encoding no better
than incidental deep encoding
- Transfer-appropriate processing
- Is deep encoding always best?
It depends upon the nature of the test
The idea that memory is best when the same mental operations are performed both at study and at test
- Morris et al. (1977) study
- Subjects performed one of two study tasks
In each case, they had to say whether a target word fit into the blank
In one condition, this was based on meaning
The _______ was on the shelf
“book” - yes or no
In another condition, this was based on sound
________ rhymes with fear
“spear” - yes or no
They were then tested using two different types of test
Standard recognition test (“Did you see ‘book’ before?”)
Rhyme test (“Did you see a word that rhymes with ‘clear’ before?”)
- Morris et al. (1977) results
- Recognition performance was better following meaning task
Rhyme performance was better following rhyming task
Deep study is not always better
- Encoding specificity
- The information in the retrieval cue must match the information stored in the memory
This will depend upon the all of the information the subject encountered at study, including the psychological state
Closely related to the transfer-appropriate processing idea
- Eich et al. (1975) study
- Subjects studied lists of words after smoking either tobacco or marijuana
Then, subjects were tested after smoking either tobacco or marijuana
Memory was best when study and test matched (although upper score of weed study was lower than cigs)
Memory contains information about the context, including the psychological state
- Optimizing memory
- Factors that maximize long-term memory retention often result in poorer short-term retention
Can lead to overestimation of learning
Optimal learning requires “desirable difficulties”
What maximizes long-term retention?
Retrieval during study
Tests are the best study events
- The spacing effect
- Jacoby 1979 procedure:
Once presented pairs:
Read: Foot Shoe
Construct: Foot S__e
Twice presented pairs:
Massed: Foot Shoe X2(read & construct versions)
Spaced: Foot Shoe, 20 other pairs, Foot Shoe (read & construct versions)
Lowest to Highest result:
read 1, read massed, Construct massed (42%), read spaced (44%), Construct 1(58%), Construct spaced (75%)
- Roediger & Karpicke (2006)
- Subjects were given a text passage to learn
Three study conditions
SSSS: four study presentations (14.2 seconds average study time)
SSST: three study presentations followed by one test (10.3 seconds average study time)
STTT: one study presentation followed by three tests (3.4 seconds average study time)
Later, they were asked how well they felt they had learned the material, and then were tested (either 5 minutes or 1 week later) on how well they retained the ideas from the passage
- Roediger & Karpicke (2006)
Estimates of learning
- SSSS (4.8) group highest followed by SSST (4.2) and then STTT (4.0)
Subjects in SSSS felt that they had learned the
material better than the other groups
- Roediger & Karpicke (2006)
- Immediate test
- Reconstructive memory
- Memory is not like a VCR
It is reconstructive
We use information in the world and our knowledge about the world to reconstruct memories
- Memory distortions
- Loftus (1977)
Subjects viewed video of car crash
They were then ask how fast the cars were going when they:
hit each other: 34.1
A week later, the subjects receiving the “smashed” question were more likely to (incorrectly) report broken glass
- Implanting false memories
- Loftus & Pickrell (1995)
Subjects presented with 3 true stories and 1 false story from this person’s past (between ages 4 and 6)
False story had realistic details from relatives
Subjects recalled 68% of true events and 29% of false events
the false events were recalled even two weeks later
Some subjects clung to the false memory even after being debriefed
- “Flashbulb” memories
- Where were you when you first heard about the World Trade Center attack?
People often have vivid perceptual memories for important/traumatic events
These are called “flashbulb” memories because they seem to be captured like a photograph
- Accuracy of flashbulb memories
Neisser & Harsch (1992)
- On the day after the Challenger explosion in 1986, subjects were given a questionnaire:
What were they doing when they heard about the explosion?
Who were they with?
How did they hear about it?
Some of the subjects were tested again ~ 3 years later
Responses coded in terms of accuracy
- Inaccuracy of flashbulb memories
Neisser & Harsch (1992)
- Subjects were quite inaccurate about details
average of 2.95 out of 7 correct responses
25% of subjects were inaccurate about all details
However, the subjects were highly confident in their responses
confidence rated as 4.17 out of 5
Many subjects produced detailed recollection with vivid details
Confidence and accuracy in memory are not closely related
- Major distortions of “flashbulb memories”
- Memory for the O.J. Simpson verdict (Schmolock et al, 2000)
Recollection (3 Days)
“I was in the computer lounge at Revelle (College) and saw it on T.V. As ten o’clock approached, more and more people came into the room. We kept having to turn up the volume, but it was kind of cool. Everyone was talking.”
Recollection (32 Months)
“I first heard it while I was watching T.V. At home in my living room. My sister and father were with me. Doing nothing in particular, eating and watching how the news station was covering different groups of viewers.”
- Why do we forget things?
The memories are lost from storage and cannot be retrieved again
The memories remain in storage, but we can’t properly retrieve them because we don’t have the right retrieval cues, or because other things interfere
We purposefully forget (consciously or otherwise)
Evidence points to retrieval theory
- Memory Repression
- Can memories be intentionally forgotten?
Freud argued that we repress unwanted or traumatic memories
Anderson & Green (2001)
Subjects were given unrelated word pairs to remember (“ordeal-roach”)
They were then given the target word (“ordeal”) under one of two conditions
“think” condition: subjects told to think about the other word in the pair
“no-think” condition: subjects told not to think about the other word in the pair
After this, they were tested on memory for the word pairs
- Anderson & Green (2001) results
- Subjects had better memory for the word pairs seen in the “think” condition compared to the “no-think” condition
This occurred even when subjects were encouraged to remember the “no-think” pairs for monetary reward!
Shows that intentional repression can cause forgetting
- Functional amnesia
- There is some evidence that people with no brain damage can become amnesic due to psychological reasons
Repression of all past memories or memories from a certain period
- Patient K (Treadway et al., 1992)
- K (53-year-old man) was discovered lying on the kitchen floor by his family in 1984
He was unresponsive until the following day
When he awoke, it became clear that he thought it was 1945 and he was 14 years old
He did not recognize his wife and two children and repeatedly asked why his mother and father were not there to visit him
His father had died 11 years earlier and mother lived thousands of miles away
The last memory that he reported was of being hit in the head with a baseball bat
Thought this was the cause of his hospitalization
This did in fact occur when he was a child
- Patient K part 2
- K acted as if it were 1945
He was fascinated by household appliances (including those he had bought previously)
He thought the family car looked like a “space car”
He feels himself to be a 14 year old stuck in the body of an adult
Frequently acts like an adolescent
- Explaining K’s amnesia
- Why did K regress to 1945?
It was the last happy time in his life
His grandmother died soon after
He moved to a new school where he was unhappy
The family house burned down in the late 1940s
He was experiencing substantial stress
He had exaggerated his credentials to get a job and was coming under scrutiny
He was very nervous about a new business venture
- The neural basis of long-term memory
- Anterograde amnesia
the case of H.M.
Neuroimaging of memory encoding
The neurobiology of long-term memory
Sleep and memory
- Types of amnesia
- Amnesia: loss of memories due to brain injury or disease
Retrograde amnesia (RA)
Loss of memories prior to the event
“soap opera” amnesia
Anterograde amnesia (AA)
Inability to form new memories since the event
Most amnesics have both RA and AA
- The case of H.M.
- H.M suffered from severe, medically intractable epilepsy
At the age of 27 in 1953, he underwent surgery to remove his hippocampus and medial temporal lobe on both sides
He has since been extensively studied at MIT
- H.M.’s amnesia
- After the surgery, H.M. was left with a severe anterograde amnesia
He has not formed any new memories since the surgery
his age or the current date
where he is living
the current status of his parents (who died long ago)
his life history since high school
He also had a temporally-graded retrograde amnesia
Worse for newer memories (closer to surgery)
- Memory dissociations in H.M.
- Despite his inability to form new memories, H.M. can still learn some kinds of new information
We will discuss this in more detail in the lecture on consciousness and implicit cognition
- Neuroimaging of memory encoding
- Both the frontal lobes and the hippocampus are important for forming new memories
- Relating brain activity to subject behavior
- Brain activity predicts subsequent memory
Anterior and Posterior LIPC, also Left Posterior Parahippocampus show higher levels of activation during encoding words later remembered words in comparison to words later forgotten
"Our studies, together with previous results
(2), suggest that what makes a verbal experience
memorable partially depends on the
extent to which left prefrontal and medial
temporal regions are engaged during the experience."
- Testing memory in animals:
The Morris Water Maze
- The rat is placed in a tub of cloudy water and must find a platform on which to stand
Rats with hippocampal damage
will search exhaustively for the
the platform - they can’t
remember where it is
Normal rats head right
for the platform.
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