Cognitive Lecture 6
Episodic & Semantic Memory 10/11/2011
History 19 Century
Herman Ebbinghaus “On Memory”
University or Toronto worldwide that played important role in study of memory
They honor his work.
Before he came around people took empirical approach to memory.
Memory is about the past, if you are brought into memory lab as a scientist you want to make sure everyone who comes in knows certain
Take what you know and look backwards to see how memory formed.
He decided to set aside fact that people coming in knew a lot already
He wanted to teach them something knew and studied how memory developed.
Behaviorists believed in nurture▯ wanted a rat and to control every experience.
He wanted to create environment where he had control over what people are learning, new information people haven’t been exposed to
He was able to bring many important variables under experimental control
Episodic memory▯ Study of episodes in one life (things that happen to you as an individual)
Central to what we do
Ebbinghaus and Experimental Control
He put a lot of thought into the stimuli asked to remember (To be remembered stimuli)
Don’t want to use something like the Prime Minister of Canada (everyone knows this)
Important to him that the person had no prior experience with the stimulus (can’t use words or famous people)
Stimulus should be relatively meaningless (no semantic associations) Didn’t want the stimulus to bring up any associations.
Decided to use nonsense syllables (consonantvowelconsonant)
3 letter stimuli, no words. (cac)
1. Retention interval (how much time passed between when studied information and when tested on it)
You wouldn’t study 2 weeks in advance and stop studying 4 days before exam things decay over time
Larger the retention interval the poorer memory will be.
Effective retention interval on memory is not as obvious as intuition might tell.
13 days vs. 12 days vs. 11 days = steadily decreasing retention interval
2. List Length (how much material do you have to study)
Shorter list length to study, you can remember more.
This would be the number of nonsense syllables.
3. Extended Practice (over learning)
Student who has good study habits, you have a system and plan things well in advanced, imagine you kept studying when you were already
ready for the exam.
Apparently there are gains to be had with extended practice.
4. Serial Order
Tells us more about memory accuracy
Example Ebbinghaus Experiment
Study list of nonsense syllables He would measure study time for 2 perfect recitations.
He allowed people to have as much time as they need to reach perfect performance
(Ex. Mistake to declare how much time you are going to devote to each subject)
Independent variable (retention variable RI)
Range: 20 or 31 days
He controlled how much time passed between the second testing.
Relearn list after RI and remeasure study time for 2 recitations.
If you have good memory base don first session it will take you less time for 2 recitations.
Calculating Retention Savings
Time 2 should take you less time to study information than time 1
Retention interval of 20 minutes
Study time before RI= 1000 seconds
Study time after Ri= 400 seconds
Savings= (100400)/1000= 60%
Maintained 60% of what you learned earlier, and the RI lengthens the lower the percent.
As time passed you see gradual decay of memory.
What happens Instead of getting linear drop you fall off cliff, doesn’t take much time at all to start forgetting things
Even in 20 minute RI people still only maintain 60% of what they learned.
1 hour down to 30%
Flattening of performance
Suddenly it stops getting bad and stays stable for a full month.
Sometimes surprise yourself by how much you can remember over long period.
After learning list until 2 perfect recitals, he rehearsed list 30 more times
Using a 24hour RI, his savings in relearning this over learned list was 64%, compared to 34% for normal learning
Graph would slope more in over learning.
Strength of the association between adjacent items on the list
(Ex. Decision between albums and CD’s, when you listen to album you listen to whole things, can’t skip from song to song, always listen to song
in particular order you know what is coming next and there is a huge anticipation)
Direction of associations forward and backward
Forward association is you have an anticipation of what is next and backward is you have feelings for what came before.
Forward: would presenting MEV evoke GOR
Backward: Would presenting GOR evoke MEV
Learned 3 lists of 8 stimuli
Relearned them again under different conditions
Same order: 1 2 3 4 5 6 7 8 (forward) Reversed order: 8 7 6 5 4 3 2 1 (backward)
Random order: 5 2 6 8 1 3 7 4
If forward associations exist, then savings on relearning same list would be greater than savings for random list
If backward associations exist, then savings on relearning reversed list would be greater than savings for random list
Same: 33% lost, or error to recall
Tewo srtudy conditions
Recall what you are seeing now, episodic memory test.
2 Memory test
Unchanged: 78% recall
Changed: 43% In theory you did not memorize that one well
Recall vs. Recognition
Recall is harder than recognition
Recognition you get a bunch of words that you have and have not studied before, have to recognize which words you saw before.
It should be easier because the information is there you just have to guess
Recall is more demanding, you have to come up with information yourself
Recall isn’t ALWAYS more difficult
Recall subjects are asked to generate previously studied items (pairedassociate)
Example where recognition can be more difficult can tell us abut how memory works
Recognition test (based on semantic)▯ Circle names recognized as a person who was famous before 1950 (29% recognition)
Recall test: author of the Sherlock Holmes stories, Sir Arthur Conan
Given cue about particular person
Rather than recognize you have to recall a theory
Long Term Memory: Retrieval
What are factors that contribute to failures to retrieve information stored in LTM?
If you encode information in certain way, likelihood you can retrieve it depends on if retrieval environment mimics original environment
Encoding Specificity Principle The probability of recalling an item at test depends on the similarity of its encoding at test to its original encoding at study
You will be very likely to retrieve something is environment is similar where you encoded information
Phase 1▯ learn pairs of words for a memory test for second word (e.g., train black remember black)
Because you remembered black that should be example where correspondence retrieval is very high
Phase 2▯ Free associate task, given word and come up with first 4 words that come to mind.
Generate four freeassociates to words (e.g., given white and generate snow, black, wool, pure).
Of four free associates, black is very likely to be on the list.
WANT black to be one of words you recall.
Phase 3▯ Recognition: which of the four freeassociates was a toberemembered word from Phase 1?
54 % correct
Of 4 words, which ones did you see in phase 1
Phase 4▯ Cued Recall When given train_____?
Mimics encoding conditions
In Phase 1 and Phase 3, poor recognition
Phase 1 and Phase 4, good recall
Sometimes when people correct in recognition could have been due to chance
Study and Test Conditions
Memory is better when test conditions match study conditions Study and test environment
Underwater vs. On shore
Emotional context of study and test
State of inebriation at study and test
If you are in particular study you are best of reproducing that in testing environment.
More likely to be able to successfully retrieve that information.
All these work
Lab 4: Encoding Specificity
Encoding: paired associates
Retrieval: encoding context
Old (same context as encoding)
Seeing exactly what we associated before
Performance should be good in old condition.
New (different context than encoding)
Strong: rockingCHAIR, or beeSTING
Weak: riverSTING or mugCHAIR Most interesting because if you compare rocking chair to cowboy chair you would think having rockingCHAIR would out perform new
What should matter is correspondence between encoding
Did you see words in CAPS earlier?
According to principle old should always outperform new
Old/Strong (waspSTING)>New/Strong (beeSTING)
Old/Weak (cowboyCHAIR) > New/Weak (mugCHAIR)
Old/Weak (cowboyCHAIR)> New/Strong (rockingCHAIR)
Old weak words were superior to strong weak words in Lab experiment.
Other memories may interfere with the retrieval of toberemembered information
Proactive▯ when learning of new material is disrupted by previouslylearned material
Something you learned at time 1 is interfering with ability to learn at time 2
Retroactive▯ when learning of new material disrupts memory for previouslylearned material
The past, something that is new interferes with something you learned earlier. • Tip of the Tongue
You have a concept clearly in mind, but can’t come up with the right word to describe it.
Another example of failed retrieval
Read out dictionary definitions of rare words, and asked subjects to identify the words defined.
1. Navigational instrument used to determine position of the starts: sextant
2. A type of carving done on whale bone: scrimshaw
3. Russian sled drawn by three horses: troika
Desire to have a lot of control over the situation, being able to tell what’s going on inside of mind.
We have a procedure we think might induce tip of tongue in someone
4. Tell us if you experience tip of the tongue, if you stopped there, how do you know all you’ve done is proven you can
produce in the lab haven’t learnt anything about memory.
5. Is there a way you can find out that it is true to being close to being successful.
If TOT, they tried to guess initial letter, number of syllables, and what it sounds like, long/short word. 6. 57% correct with initial letter
7. Scrimshaw: something like Sanskrit Cognitive Lecture 7 10/11/2011
What is the nature of network in which information is stored?
Organization of Semantic Memory
Individual concepts represented as “nodes” in a memory network
Concepts/nodes that are semantically associated are interconnected
Degree of semantic relatedness between two concepts is represented by the strength of the interconnection between their nodes
Prof sees no connection between hockey and figure skating but daughter sees strong semantic connection
Thick line is strong semantic connection between two concepts.
If you activate this network, like saying hockey or a hockey related term, you are going to activate hockey node and spread to other nodes
(things that have strong interconnection will receive activation)
When one concept is activated, the activation “spreads” to other concepts whose nodes have strong interconnections with the activated node
Evidence For Network Organization: Semantic Priming
Lexical decision task:
Two letterstrings shown in succession
Some words, some nonwords
Are both strings words? Y or N
Speed can come into play, example of using chronometry Cognitive Lecture 7 10/11/2011
See differences in speed depending on stimulus
Ignore Negative pairs
Positive pairs are words in which you make guess judgments. Cognitive Lecture 7 10/11/2011
When you prime semantic network with bread, nodes spread to other nodes, you are primed for butter
If you prime network with nurse, you would think of nurse related things not butter.
Limits of Spreading Activation
Activated nodes have a fixed capacity for emitting activation
If you prime a network you might not be surprised to hear that only so much of network can spread around.
Thus the more interconnections that a node has, the less activation that will spread to any interconnected node
When you have particular concept that is very interconnected (Leaf’s fan) you might have many associations
The less associations with a node, the more energy that can be transferred to the interconnected nodes.
Evidence: the fan effect
Learn a set of sentences
The doctor is in the bank
The lawyer is in the park
The lawyer is in the church
Recognition test: Was this sentence in learning set? Cognitive Lecture 7 10/11/2011
Degree of fan
11 was lower than 12, 21 was lower than 22
We were slower than the reference data
11 was the slowest and 22 was the fastest.
12 and 21 should be equal. Cognitive Lecture 8 10/11/2011
Video ▯ amnesiac Mike
Main structure involved: hippocampus
Memories of experiences before the injury intact (anterograde amnesia)
Problems occurred 4 months after a car accident: seizure and then 2 week coma (twice)
Damage of the hippocampus
LTP: how memory is stored
With tactile sense Mike is able to function well
Has a routine, following it helps
Cannot rely on his memory
Hippocampus in conjunction with other structures consolidates memories
Some patients have amnesia and are aware of their amnesia, others are not
Video ▯ fictional character Leonard
Shortterm memory loss patient
Cannot find a pen with which to write down information about Natalie (woman that insulted him and his wife)
From the film “Memento”
If a person is profoundly amnesiac, they can have implicit memories
Ex. emotional warmth/coldness toward people they do not remember consciously
Causes of Amnesia
Stroke very common
Epileptic activity H.M. (famous amnesiac patient) also had seizures Cognitive Lecture 8 10/11/2011
Tumors can hinge on tissue and prevent memory development
Chronic alcohol abuse vitamin B1 deficiency (thiamine)
Oxygen deprivation if resolved but caused damage, temporal lobe first affected (LTM)
Inability to form new memories or learn new things after onset of amnesia
More prominent (do not forget loved ones, but would forget the nurses caring for them)
Inability to recall events and information learned from before the onset of amnesia
Often both AA and RA
Recovery with time
Permanent loss of memories for events immediately preceding injury (RA) and for events occurring during time of AA
Symptoms not limited to memory loss
After 5 months patient has no recall
After 8 months patient shows signs of improvement (in both RA and AA)
After 16 months patient show significant improvement Cognitive Lecture 8 10/11/2011
HM: severely epileptic whose seizures originated in the medial temporal lobe
Surgery went wrong in that it affected his cognitive performance
Successful in eliminating seizures
Seizures so debilitating that he could not function properly
Bilateral medial temporal lobectomy
Had severe AA
RA for three years preceding surgery
However HM could remember the distant past
Vitamin B1 thiamine deficiency because of poor diet
Deficiency in brain function, particularly memory (AA and RA)
Chronic alcohol abuse can cause brain damage particularly to areas involved in memory
A wider range of memory impairments than other amnesic populations
A steady deterioration, with memory impairment in the early stages being followed by other cognitive impairments
Loss of memory, you might think it is good candidate for studying memory loss.
In reality, it is not considered good candidate for producing good patients
More interesting patient is one who has selective memory deficits, not total memory loss.
Why are cognitive psychologists interested in amnesia?
Memory is too complex to be a single process in an informationprocessing model Cognitive Lecture 8 10/11/2011
Some people believe recognition is far too complex for there to be single recognition system, face recognition might be unique in some way.
Cognitive neuropsychology came along and found unique sets of patients that proved different types of recognition.
Memory seems to bee too complex in ways we use it in our everyday lives.
Widespread Brain Damage
This is why amnesia patients are not good candidates for studies.
Is Short Term Memory Distinct from Long Term Memory?
There are many amnesiacs with profound LTM deficits but with intact STM
Prosopagnosia one side is much more common than the other in double dissociation.
Many amnesiacs who have problems with LTM but short term memory is intact
As long as amnesia can keep something in mind, they are able to hold on to that information.
The act of rehearsing short term memory is not going to buy entry into long term memory
Won’t truly remember a new person on a subconscious level. Cognitive Lecture 8 10/11/2011
Amnesia with Intact STM
Digit Span: Many are good as normal people
Span is quite “normal”
It is possible to have normal conversation with most patients with amnesia
Memory aspect of conversation require only one person to talk at a time, if you say something that inspires response, someone might interrupt
if they have bad social skills, or you may hold it in working memory until person is finished talking.
Fact they have short term memory is synonymous with articulatory rehearsal loop (span task)
AA only shows itself with sufficient delays.
10 second Tom, he forgets what happened after 10 seconds can’t remember anything beyond that time frame.
Insert brief retention interval chances are you can easily demonstrate their problems by doing so.
Show list of words, let time pass, they will struggle if not completely fail.
There are many amnesiacs with profound LTM deficits but with intact STM
Amnesia with Intact LTM
There are a few reported cases of patients with STM deficits and intact LTM.
Patient KF brain injury from motorcycle accident
No difficulty on longterm learning and recall
Digit span was impaired (2 digits)
Small recency effect in freerecall
Modal Model problem is that short term memory is necessary for long term
A lot of things that happen to you that you hold on to for a long time that you never had to rehearse to remember.
You don’t have to do anything because you are actively in the moment and are not worrying about it.
You can have long term memories sometimes without rehearsal.
Most neuropsychologists would agree that double dissociation is evident.
This doubledissociation was considered strong evidence for separate ST and LT memory storage
Other Memory Distinctions (LTM)
Episodic▯ Specific events which occurred in a particular place at a particular time
Events in your own life. Cognitive Lecture 8 10/11/2011
Remember list of words, time passes, shown again were these the same words?
Semantic▯ Our stock of knowledge about the world
Prime minister? Most can answer this.
Something detached from its source.
Evidence from amnesia Hypothesis:
Amnesia typically affects episodic rather than semantic memory.
Episodic: amnesiacs have a deficit in st