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A pioneer of the scientific study of memory: Hermann Ebbinghaus (1850

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Title: A pioneer of the scientific study of memory: Hermann Ebbinghaus (1850


1
A pioneer of the scientific study of
memoryHermann Ebbinghaus (1850 1909)
  • worked as philosopher at university in Berlin
  • inspired by lawfulness of relation between
    physical properties of perceptual stimuli and
    psychological sensations discovered in field of
    psychophysics
  • e.g. Fechners law Webers law

2
Classic finding in psychophysics Webers law
standard line just-noticeably-longer line
3
A pioneer of the scientific study of
memoryHermann Ebbinghaus (1850 1909)
  • performed experiments on himself published in
    classic volume entitled Über das Gedächtnis
    (1885)
  • famous because - pioneer of empirical approach
    - inventiveness as experimenter

4
Memory experiments by Ebbinghaus
  • new systematic and controlled study of
    memory in laboratory
  • e.g. - created new stimulus material
  • - applied scientific accuracy (use of
    metronome) - established method to quantify
    memory performance and describe regularities

5
Memory experiments of Ebbinghaushow to
investigate retention of newly learnt material
  • invented lists of 16 nonsense syllables to
    minimize influence of
  • learners history
  • goal study memory in pure form
  • introduced criterion for successful learning
  • (2 errorless recitations)
  • introduced savings method to measure retention /
    forgetting of lists

6
Memory experiments of EbbinghausExample of
memory task
  • memorize the following (shortened) list
  • falem
  • zeb
  • xalvo
  • monul
  • rull
  • namak

7
Memory experiments of Ebbinghaus Examination of
forgetting curve with savings method
  • calculation of savings scores to measure
    performance
  • finding
  • most forgetting occurs right after learning
  • -gt approx. 50 in first 40 min
  • -gt relationship between delay and forgetting
    not linear

8
Memory experiments of Ebbinghaus Other important
findings
  • list-length effect amount of information and
    ease of learning not related in linear one-to-one
    fashion disproportionate increase in difficulty
    with more than 7 syllables
  • beneficial effects of distributed practice for
    repetitions

9
Memory research of Ebbinghaus Why is it such a
major contribution?
  • discovery of important regularities (basic
    findings)
  • memory can be studied empirically with
    experiments
  • mental phenomena can be studied even if they are
    not linked directly to physical world via
    perceptual organs

10
Memory research of Ebbinghaus What was missing?
  • research criticized as atheoretical
  • but emphasis on observations rather than
    theories typical for early research in new field

11
The Ebbinghaus Legacy Verbal-learning research
1950s 1970s
  • behaviourist tradition (S-R / S-S associations)
  • mind as black box
  • systematic study of factors affecting verbal
    learning
  • e.g. numbers of repetitions, presentation time
    word frequency
  • later replaced by information-processing
    approach growing emphasis on mental
    representations

12
Richard Semon (1859 1918) An early memory
theorist
  • work strongly influenced by evolutionary biology
    (Darwin)
  • interest in commonality between heredity and
    memory
  • aspect of biological tissue that allows effects
    of experience to be preserved over time
  • three stages of memory (new terms invented)
  • Engraphy acquisition of new information
  • Engram enduring change in nervous system
    that allows for retention
  • Ecphory recovery of stored information

13
Richard Semon (1859 1918) An early memory
theorist
  • concept of engram motivated much research on
    brain basis of memory in 20th century
  • What are the manifestations of memory traces in
    the brain?
  • concept of ecphory strongly influenced
    cognitive psychology of memory in 1970s
    (Tulving)
  • How can a dormant memory trace be awoken?
  • -gt emphasis on processes at time of retrieval
    (recovery) of info from memory
  • -gt emphasis on presence of suitable retrieval
    cues

14
Information-processing approach to
memory(starting 1960s)
  • motivated by emerging of computers and computer
    science as scientific discipline
  • human mind can be understood with computer
    metaphor
  • e.g. storage of information in different
    memory buffers
  • RAM vs hard-disk lt-gt STM vs LTM
  • central importance of information and mental
    representations (mind not a black box)
  • focus on cognitive processes that deal with (e.g.
    create, access, compare) mental representations

15
Information-processing approach to memoryA
practical example
16
Information-processing approach to memoryBasic
framework
  • 3 stages of processing for manipulation of mental
    representations
  • Encoding (acquisition of info)
  • Storage (retention of info)
  • Retrieval (recovery of info)

17
Information-processing approach to
memoryTypical research questions
  • do we store different types of memory
    representations? Are they retained equally well?

bear
e.g.
18
Information-processing approach to
memoryTypical research questions (contd)
  • do we need attentional resources to encode new
    information into memory?
  • e.g. can be studied through examination of
    influence of distraction
  • can information in memory influence our thoughts
    and actions unconsciously?
  • e.g. can be studied in patients under
    anesthesia

19
Information-processing approach to
memoryApplication to Ebbinghaus research
  • what were the syllables you memorized in the
    example I gave earlier?

20
Information-processing approach to
memoryApplication to Ebbinghaus research
  • which of the following syllables was on the list?
  • halek or xalvo
  • -gt forgetting curves will vary depending on
    whether syllables need to be recalled or
    recognized
  • -gt more detailed analysis of cognitive processes
    required to understand regularities in forgetting

21
Information-processing approach to
memoryApplication to Ebbinghaus research
  • e.g. zeb may or may not make you think of
    zebra at encoding
  • -gt consequences for subsequent remembering
  • -gt even learning of simple stimuli such as
    non-sense syllables is affected by variations in
    cognitive processing and pre-existing knowledge
  • -gt memory cant be investigated in pure form

22
Cognitive-neuroscience approach to memory
  • multidisciplinary approach (psychology, computer
    science, neurology, radiology)
  • emphasis on relationship between behaviour,
    cognition, and the brain
  • central question how dos the brain allow humans
    to learn and remember?
  • general idea to understand the organization of
    memory (e.g. how many different types?) we should
    focus on neurological and cognitive aspects

23
Cognitive-neuroscience approach to
memoryDifferent types of investigation
  • lesion studies in neurological patients
  • examination of effects of different types of
    brain damage on memory processing
  • functional neuroimaging
  • examination of brain activity in healthy
    individuals while they perform memory tasks
  • computational modeling
  • testing of quantitative memory theories with
    computer models that incorporate a brain-like
    organization (neural networks connectionist
    models)

24
Cognitive-neuroscience approach to
memoryExample of functional neuroimaging study
  • do different parts of the brain become active
    when we try to remember pictures as compared to
    words?

pictures
words
25
Memory experiments of Ebbinghaus Examination of
forgetting curve with savings method
  • most forgetting happens immediately after
    learning

-gt approx. 50 in first 40 min
26
Forgetting on Brown-Peterson taskwith consonant
trigrams
  • Repeat HLM
  • 2. Distractor task Count in 3s from 492
  • 3. What were the letters?
  • many trials with different delays
  • after 6 sec only 40 correct recall

27
Forgetting on Brown-Peterson taskwith consonant
trigrams
  • findings suggest short-lived memory component
    different from type of memory studied by
    Ebbinghaus

28
Something special about short lists
  • Ebbinghaus lists with up to 7 nonsense syllables
    are forgotten at different rate than lists with
    more items
  • G. Miller (1956) immediate memory span
  • Magical number seven, plus or minus two
  • holds for digits, letters, words
  • (digit span, letter span, word span)
  • -gt suggests that short lived memory
    component has limited capacity

29
Further examination of immediate memory span
  • integration of information through chunking
    possible
  • e.g. letters in meaningful word
  • letters in acronyms (USA, IBM)
  • area code in phone number
  • chunks are basic storage units in short-lived
    memory component

30
Chunking produces similar forgetting curve on
Brown-Peterson task with words and trigrams
31
Consequences of findings with Brown-Peterson task
and with memory span in 1960s
  • new notion memory is not unitary
  • there may be at least two separate stores that
    work with different cognitive mechanisms
  • they seem to differ in terms of forgetting rates
    and capacity
  • -gt longer lasting component may not have any
    capacity limitations
  • e.g. Ebbinghaus could remember lists of 40
    and more nonsense syllables
  • everyday observations suggest that
    memory capacity for life events unlimited

32
W. James Primary vs secondary memory
  • Primary memory
  • it was never lost its date was never cut off
    in consciousness from that of the immediately
    present moment in fact, it comes to us as
    belonging to the rear-ward portion of the present
    space of time, and not the genuine past
  • -gt extended present
  • Secondary memory
  • the knowledge of a former state of mind after
    it has already once dropped from consciousness
    or rather it is the knowledge of an event, or
    fact, of which we have not been thinking, with
    the additional consciousness that we have thought
    or experienced it before

33
Different proposals for two-store models
  • W. James (late 1800s)
  • primary memory vs secondary memory
  • still in consciousness vs lost from
    consciousness
  • Atkinson Shiffrin (1968)
  • short-term memory (STM) vs long-term memory
    (LTM)
  • Baddeley (1980s)
  • further theoretical development of concept of
    STM -gt renamed working memory (WM)

34
Consequences of findings with Brown-Peterson task
and with memory span in 1960s
  • controversy over need to postulate two stores
  • philosophy-of-science argument relevant
  • more parsimonious theory better than more
    complicated one if it can explain the same
    findings (principle of Ochams razor)
  • -gt is there sufficient number of critical
    findings that single-store theory cannot
    explain?

35
Forgetting mechanisms in STM vs LTM
  • typical explanation of forgetting on
    list-learning tasks (à la Ebbinghaus) and others
    task studied in verbal-learning research
    interference
  • e.g. paired-associate learning task
  • First list Second list
  • car ball car fridge
  • tree screen tree foot
  • table paper table ocean
  • door sports door hair

36
Forgetting mechanisms in STM vs LTM
  • retroactive interference on paired-associate
    learning task
  • What was linked word from first list? tree
    ?
  • door ?
  • -gt learning of second list impairs recall of
    first list
  • interpretation in behaviourist learning theory
  • associations between pairs in first list
    weakened through learning of second list
  • application in everyday life
  • previous postal code after move

37
Forgetting mechanisms in STM vs LTM
  • suggestion for forgetting on Brown-Peterson task
    trace decay (fading)
  • - occurs as soon as stimulus absent
  • - can be prevented through active rehearsal
  • - thought to be different from
    interference-related forgetting on LTM tasks
    (notion later challenged)

38
Other evidence to support distinction between STM
and LTMSerial-position curve in free recall task
recency effect
primacy effect
39
Effects of presentation rate and delay on serial
position curve (Glanzer Cunitz, 1966)
40
Interpreting effect of presentation rate and
delay in Glanzer Cunitzs experiment
  • presentation rate
  • more rehearsal allows for better transfer of
    info from STM into LTM in primacy portion
  • delay
  • trace-decay in STM eliminates recency
  • -gt different experimental manipulations have
    different effects on recency and primacy
    portion of curve
  • -gt suggests that primacy and recency effects
    reflect operation of different stores (LTM,
    STM)

41
What makes a list difficult for STM (Baddeley,
1966)?
unrelated
semantically similar
acoustically similar
detrimental effect of acoustic but not semantic
similarity on immediate recall of short word lists
42
Interpretation of difficulty findings in
Baddeleys STM experiment
  • detrimental effect of acoustic similarity on
    recall of brief lists suggests that info is
    coded phonologically (in terms of sound) in STM

43
Evidence suggesting semantic code for LTM
  • prose passage experiment by Sachs (1967)
  • e.g. sentence heard as part of story
  • she watched the kids on their way home
  • LTM test after 20 min delay
  • Was the following sentence part of the story?
  • - she watched the birds on their way home
  • (no easy few errors)
  • - the kids were watched by her on their way home
  • (no difficult many errors)
  • - she observed the kids on their way home
  • (no difficult many errors)

-gt good recognition of semantic but poor
recognition of verbatim information
44
Interpretation of findings on retention of
verbatim info in LTM
  • poor recognition of verbatim info with good
    recognition of semantic info suggests that info
    is coded semantically (in terms of meaning) in
    LTM

45
What kind of memory is impaired in neurological
patients suffering from amnesia?
  • amnesia can occur as result of sudden brain
    damage
  • (e.g car accident, stroke)
  • - patients do not remember anything from time
    since injury
  • - patients have difficulty keeping track of
    daily events
  • - patients have difficulty learning names of new
    people (e.g. physicians and nurses on ward)
  • - patients have difficulty learning way around
    in new environment (e.g. hospital)
  • critical question does amnesia affect STM, LTM
    or both?

46
What kind of memory is impaired in neurological
patients suffering from amnesia?
  • general findings in amnesic patients
  • normal STM capacity on digit-span task
  • normal forgetting curve on Brown-Peterson
    task
  • normal receny effect on list learning task
  • suggests that LTM but not STM is affected by
    amnesia

47
Additional evidence showing that memory deficit
is specific to LTM in amnesiaFindings with
span 1 task (Drachman Arbit, 1966)
lists larger than STM span extremely difficult to
learn for patients
48
What do patient studies tell us about distinction
between STM and LTM?
  • observed pattern of deficits across studies
  • one type of brain damage leads to
    impairments in LTM but not STM
  • other type of brain damage leads to
    impairments in STM but not LTM
  • -gt suggests that LTM and STM rely on proper
    functioning of different brain structures
  • -gt suggest that LTM and STM have distinct neural
    basis

49
Characteristics of two separate memory stores (as
widely accepted in 1970s)
Note concept of STM different from use of term
in everyday life
50
Atkinson Shiffrins modal memory model
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