learning and memory – 578 fall 2012 reproductive and...

Learning and Memory – 578 Fall 2012

Reproductive and Reconstructive Memory

Two early approaches to studying memory:

Ebbinghaus (1885)

Bartlett (1932)

Two components of memory:

Process● how is information retained or retrieved?

Representation● what information is retained or retrieved?

Ebbinghaus (1885)

How do we remember?

How do factors such as time and repetition influence memory performance?

Ebbinghaus (1885)

● memory formed through association- repetition → association strength

● processes underlying memory- encoding (learning) factors- retrieval factors

● interested in “pure” memory- used nonsense syllables (CVC)- content without prior association

Ebbinghaus (1885)

encoding

● introduced the learning curve ● more repetitions → better retention● long series → requires more repetitions

Ebbinghaus (1885)

retrieval

● recall- free - serial

● recollection (recognition)● savings

Ebbinghaus (1885)

serial position curve

Ebbinghaus (1885)

forgetting curve

Bartlett (1932)

What do we remember?

What is the nature of the representation?

Bartlett (1932)

● memory is not a storehouse of traces- memory is dynamic, not static- remembering is constructive

● memory is relative, not absolute- schema: a conceptual standard- “organized setting” - context?

● awareness is not necessary for memory

Bartlett (1932)War of the Ghosts

Bartlett (1932)

recall of the story was distorted – much like the “whispers” game

● words were changed- 'canoe' → 'boat' , 'paddles' → 'oars'

● concepts changed- 'hunting seals' → 'fishing'

● information was omitted- particularly when hard to interpret

Ebbinghaus: memory can be very accurate, even for nonsense syllables.

Bartlett: memory can be distorted, even for meaningful material.

Are there two kinds of memory?

Where did these approaches lead?

Ebbinghaus: focus on features of memory

● capacity● duration● structure

Capacity of iconic memory

Sperling (1960)

whole report → 35%

partial report → 75%

Duration of short term memory

Peterson & Perterson (1959)

trigram presented, then interference task (e.g. count backwards from 50)to prevent rehearsal

test at 3 secs → 50% retrievaltest at 18 secs → 5% retrieval

Capacity of short term memory

George Miller (1956)

magic number 7 +/- 2

chunking changes meaning of capacity

Memory structures

Atkinson & Shiffrin (1968)

Bartlett's influence

● memory for common objects● eyewitness reports● autobiographical memory

Memory Observed (Neisser, 1982)

Nickerson & Adams – memory for a penny

errors: omission, incorrect location, wrong side, wrong side & incorrect location

errors:50% head direction42% mislocation of remembered feature

Eyewitness Reports

Loftus & Palmer (1974)subjects were asked to estimate speed of cars that hit, smashed, collided, bumped, contacted

results:

Brief digression: role of context

encodingBransford & Johnson (1972): comprehension a la Bartlett

retrievalTulving & Thomson (1973): encoding specificity

Bransford & Johnson (1972): comprehension a la Bartlett

Bransford & Johnson (1972): comprehension a la Bartlett

Autobiographical Memory

Brewer (1988)● UGs cued to record events by beeper● recording over several weeks● tested 0, 21, 41 months after recording● 60% of events recognized

results:● actions > thoughts● events in unique location > familiar loc● rare actions > frequent actions

No matter what type of memory, somehow input must be processed to endure beyond the present moment

This is the role of consolidation

Memory Consolidation

Georg Elias Müller (1850–1934) ● introduced the term “consolidirung”● learning & memory should exhibit lawful properties

● paired associate nonsense syllables● perseveration - transient activity in the brain during encoding (type of STM)

● discovered retroactive interference● consolidation takes ~ 10 mins

Temporally graded retrograde amnesia:

loss of recent premorbid memories is greater than for older premorbid memories

Why?

Ways in which consolidation fails

(1) decay - perseveration time inadequate (2) interference - competing activation

Standard Consolidation Theory

● hippocampus needed to form memory● memory consolidates in extra-hippocampal

areas (e.g., neocortex)

Consolidation Theory Assumptions

Equivalence: hippocampus affects all declarative memories equally

Duplication: consolidated memories in extra-hippocampal areas are identical to original

Resilience: consolidated memories are invulnerable to change

Support for the standard consolidation theory?

TGRA (temporally graded retrograde amnesia)

● recent memories are vulnerable● hippocampal damage disrupts consolidation● older memories are consolidated in extra-

hippocampal areas so remain intact

However...

some patients with hippocampal damage do not display TGRA

Multiple Trace Theory

● hippocampus needed to recall episodic memories● each recall creates a new trace● multiple traces become schematized, lose details → semantic memory● semantic memory not vulnerable to hippocampal damage → ungraded RA

Transformation Hypothesis (Winocur, Moscovitch)

● consolidation in extra-hippocampal areas involves schematization● contextual memories remain in hippocampus● memory representations not equivalent● TGRA when semantic memory tested based on transformation progress● no temporal gradation when episodic memory tested

Reconsolidation

● memory retrieval involves hippocampus● retrieved memories are labile● retrieved memories are reconsolidated

assumes memory traces are equivalent

Winocur & Moscovitch (2011)

● context-dependent memory resides in hippocampus – context-free in extra-hippocampal areas

● hippocampal lesions affect context- dependent, but not context-free memories

Questions and Issues

● How do encoding conditions affect memory formation?● Are there differences in the degree to which memories are schematized?● Is there a capacity or temporal limit to what can be represented in hippocampus?● Does hippocampal damage affect the encoding and/or the retrieval of memories?● What is a memory trace?