• 3 stages of processing for manipulation of mental representations:

Encoding (acquisition of info)Storage (retention of info)Retrieval (recovery of info)

Information-processing approach to memory:

basic framework

time

Encoding Retrieval

Storage

Episodic memory: Encoding processesHow do we acquire information about episodes?

• Role of repetition / practice• Role of attention• Role of intention• Role of level of processing / elaboration• Role of organization

Episodic memory: Encoding processesRole of organization

• Bousfield experiment (1953)

+ list with 60 unrelated words+ other list with 60 words from 4 semantic categories (animals, boys’ names, professions, vegetables); presented in scrambled order

two major results:

+ better recall of words from organized lists+ subjects show tendency to recall words in related clusters

->attempt to impose organization on info to help understand and remember it

application: learn new names at family reunion

Benefits of more complex organization at encoding

Results:

+ demonstration of hierarchy at learning: 65% words recall

+ hierarchy obscured at learning: 19% words recall

Experiment by (Bower, 1969)

Presentation of words with or without visible semantic hierarchy at encoding

Episodic memory: Encoding processesRole of organization

• people show spontaneous tendency to organize material even if no objective principle is present in material -> subjective organization (E. Tulving)

Experiment by Tulving, 1962Word list: apple bell table coffee school lamp

car roof potato shoe disk paint

+ several learning trials; words in different orders

+ after each learning trial: free recall

major result:+ people recall words in same clusters on

different trialse.g. subject 1 always school – coffee

…… subject 2 always school – apple

……

Episodic memory: Encoding processesRole of organization

benefits of organization are not limited to verbal information (Mandler et al. 1976/1977)

-> people remember location of objects better if organized in a room (3D organization with floor and ceiling)

Episodic memory: Encoding processesRole of organization and levels of processing

• General point 1:

research on LoP and on organization shows that successful encoding of new information relies on linking incoming new information to existing semantic knowledge

e.g. think of Bower’s minerals experiment

-> organization won’t have benefits if no existing knowledge about hierarchical organization (e.g. metals vs stones)

• General point 2:

even though much of what we encode happens without intention to memorize (LoP), memory performance can still be improved by specific attempts to commit new info to memory

-> strategic aspects of memory(people can actively take control to

improve memory and avoid failure in specific situations)

e.g. waitress’ effort in restaurant to keep orders from different customers apart

-> use of mnemonic strategies

Episodic memory: Encoding processesRole of organization and levels of processing

• General point 3:

research on organization and LoP suggests that way in which info is encoded also determines how it can best be accessed later (i.e. what cues will help most)

e.g. experiment with minerals what were the rare metals I saw earlier?

-> encoding benefits closely linked to retrieval benefits

Episodic memory: Encoding processesRole of organization and levels of processing

• 3 stages of processing for manipulation of mental representations:

Encoding (acquisition of info)Storage (retention of info)Retrieval (recovery of info)

Information-processing approach to memory:

basic framework

time

Encoding Retrieval

Storage

Episodic memory: Can there be failures in storage processes?

• General observation:

memory failure is not always due to insufficient encoding; it occurs even when successful encoding shown

failures due to problems in storage usually referred to as forgetting

e.g. Ebbinghaus’ forgetting curve

Episodic memory: Does forgetting occur for real life episodes?

• What did you do for Thanksgiving last fall?

Episodic memory: Does forgetting occur for real life episodes?

• study by Friedman & deWinstanley (1998) on memory for latest Thanksgiving dinner in 500 college students

+ follow-up of memory for details and vividness over 6 months

Findings:

+ vividness declines more rapidly at beginning of delay

+ memory for details also forgotten more rapidly first

+ ‘gist’ of event remembered well even after 6 months e.g where was it, what did you eat, unique happenings

BUT general semantic knowledge of help

-> forgetting of episodes follows familiar course but not all-or-none phenomenon

Episodic memory: Why do we forget?

• basic question that came up in research on STM vs LTM:

Why do we forget??

i.e. why is information lost from episodic memory even when it was properly encoded to start out with?

• two major explanations:

- transience / trace-decay -> fading of stored information over time

- interference -> replacing of stored by new information

• McGeoch (1932): critique of trace-decay theory

Episodic memory: Why do we forget?

• McGeoch (1932): gist of interference theory

in normal experiments and in real world there are always activities or events that intervene between encoding and retrieval of information

-> these activities produce retroactive interference and are critical determinants of forgetting; not time passage as such

Episodic memory: Why do we forget?

Episodic memory: Forgetting mechanisms

• testing of interference hypothesis in verbal learning study by McGeoch & MacDonald (1931)

+ learning of list with 10 adjectives until recalled perfectly+ effects of 10 min delay filled with different tasks

-> is there retroactive interference?

• testing of interference hypothesis in verbal learning study by McGeoch & MacDonald (1931)

two major findings:

+ type of interpolated activity has clear effect on memory performance for previously learnt

list

->most detrimental effect with similar, semantically related material

application: remembering lunch at UCC last Thursday

+ even subjects in ‘rest’ condition show some forgetting

Episodic memory: Forgetting mechanisms

• even subjects in ‘rest’ condition show signs of forgetting in McGeoch & MacDonald’ s experiment

Why??

- answer of early believers interference hypothesis:

proactive interference

i.e. detrimental effect of mental activities / learning subjects engaged in before entering the experiment

Episodic memory: Forgetting mechanisms

• evidence for proactive interference in list learning study with up to 20 different lists

(Underwood, 1957)

Episodic memory: Forgetting mechanisms

• implications of idea of proactive interference:

forgetting in any given experiment is due in part to proactive interference from the subject’s past language use

- difficult to test, but prediction possible:more frequently used words in daily language

should be more difficult to learn due to higher interference

- findings: + no convincing evidence to support prediction

+ also: forgetting occurs even for nonsense syllables (without prior exposure)

-> interference theory cannot explain forgetting entirely

Episodic memory: Forgetting mechanisms

Testing of interference hypothesis in sleep study (Jenkins & Dallenbach, 1924)

more forgetting in students with interpolated study activity during day-> support for interference hypothesis; difference can’t be due to fading / trace decay

• problems in interpretation of Jenkins & Dallenbach’s sleep study:

- learning occurred at different times of day (not equally good for learning)- when experiment repeated with sleep during day, sleep (as compared to wakening) does not reduce forgetting as much

-> difference in interference between sleep and waking

not whole story-> benefits of sleep go beyond reducing interference:

consolidation

Episodic memory: Forgetting mechanisms

• basic idea of consolidation:

+ initial memory representation fragile, consolidation makes info resistant against forgetting

+ changes in brain that allow the mind to retain info do not all occur during encoding but develop over time (allow info to ‘sink in’)

+ some physiological / neurochemical processes of consolidation tied to natural nocturnal sleep cycle

-> non-REM sleep thought to be critical component for consolidation of info in episodic memory

Episodic memory: Processes working against forgetting

Episodic memory: Processes working against forgetting

0

5

10

15

20

25

30

35

early sleep late sleep

(more non-REM)

(more REM)

typical pattern of findings in studies examining effect of sleep on retention of word list (e.g., Phihal & Born, 1997)Improvement as

compared to pre-sleep testing

• recent advantages in study of physiological and molecular processes underlying memory allow researcher to study trace decay and consolidation without encountering ‘philosophical’ problem pointed out by McGeoch (1932)

e.g. learning-induced protein synthesis and gene

expression -> require time -> lead to structural changes in synapses (change in

communication between neurons)-> require brain structure ‘hippocampus’ for episodic

memory formation

Episodic memory: Processes working against forgetting

• interference theory vs consolidation theory:

Which theory is right in explaining forgetting?

-> certain that both factors determine degree of forgetting when info is processed in episodic

memory; explanations not mutually exclusive

-> consolidation likely linked to interference processes

BUT theories traditionally address forgetting at different level of explanation (neural vs cognitive)

Episodic memory: Why do we forget?

• 3 stages of processing for manipulation of mental representations:

Encoding (acquisition of info)Storage (retention of info)Retrieval (recovery of info)

Information-processing approach to memory:

basic framework

time

Encoding Retrieval

Storage

Episodic memory: Processes at retrieval

• can memory fail at time of retrieval?

e.g. think of tip-of-the-tongue phenomenon

relates to difference between accessibility and availability

Availability: is info stored?

Accessibility: can stored info be accessed in given situation?

Episodic memory: Retrieval and interference

• Tulving & Psotka experiment (1971):

Does retroactive interference reflect problems in availability vs accessibility?

- initial learning of list of with 24 words from 6 different categories (e.g. buildings, flowers, tools, metals, professions, cars)

- afterwards learning of many additional lists

How does # of additional list affect recall of first one?

-> answer depends on whether free recall or cued recall (with category cues) is used

Episodic memory: Retrieval and interference

findings in Tulving & Psotka experiment:

•typical pattern of interference seen with free recall: increasingly poorer performance with increasing # of lists

•when category cues provided () hardly any deterioration with increasing # of lists

-> poor performance does not always reflect lack of availability

Episodic memory: Processes at retrieval

• results from experiment by Tulving & Psotka show that what looks like forgetting can actually be retrieval failure

further support for idea:

study with one learning and multiple recall attempts (Tulving, 1967):

learning -> recall -> recall -> recall

-> findings show that correctly recalled items can vary from recall block to recall block

-> suggests changes in accessibility (temporary retrieval failure) across situations

Episodic memory: Retrieval processes

• systematic study of role of retrieval processes in remembering started with work of Canadian psychologist Endel Tulving

(who also introduceddistinction betweenepisodic and semanticmemory)

Episodic memory: Retrieval processes

• given that retrieval cues are important to access information in episodic memory:

What makes the best retrieval cue to recall words from

list?

Perhaps, most strongly associated word in our language?

target : sky weak associate: clear

strong associate: blue

Episodic memory: Retrieval processes

•systematic manipulation of retrieval cues

Tulving & Osler, 1968

at study: CITY – dirty

at test: free recall??

cued recall with original low assoc. cue dirty ??

cued recall with new high assoc. cuevillage ??

findings: +cued recall better than free recall+original cue better than new highly

associated cue (not studied)

Episodic memory: Retrieval processes

• Tulving & Osler, 1968

finding: + original cue better than other highly associated cue

-> association between cue and target in language as such not critical

-> critical whether cue was present when target was originally encountered

Episodic memory: Retrieval processes

• subsequent generalization:

to be effective, retrieval cue does not have to be present at encoding literally; cue just has to bring to mind what person thought about at encoding

Study: The fish attacked the swimmer

Test Group 1: What was the sentence that had to do with ‘shark’?

Test Group 2: What was the sentence that had to do with ‘fish’?

Cue in Group 1 more effective than cue in Group 2

Episodic memory: Retrieval processes

• further evidence that specific way in which info was thought about at encoding determines effectiveness of retrieval cue:

experiments by Bransford et al. (1974)

Study –Group 1: the man tuned the PIANOStudy –Group 2: the man lifted the PIANO

Cued recall: something heavy ?? something melodious ??

Results: Group 1 remembers PIANO better with second cue Group 2 better with first cue

Episodic memory: Retrieval processes

• theoretical interpretation of relationship between info at encoding and cue at retrieval:

encoding-specificity principle (Tulving & Thomson, 1973)

specific encoding operations determine what is stored, and what is stored determines what retrieval cues are effective in providing access to it

What would be an effective cue to recall this picture?