Implicit memory

1
Implicit memory

• Schacter article distinguishes between implicit
  and explicit memory
• it surveys historical observations regarding
  implicit memory
• then it reviews more recent research and
  theoretical accounts

2
Implicit memory

• implicit memory
• occurs when previous experiences facilitate
  performance on a task that does not require
  conscious recollection of those experiences
• explicit memory
• occurs when the task requires conscious
  recollection of past experiences

3
Implicit memory

• Historical survey
• Maine de Biran proposed that after sufficient
  repetition a habit can be executed automatically
  and unconsciously without awareness of the act
  itself or of the previous episodes in which the
  habit was learned
• Maine de Biran also developed a form of multiple
  memory system

4
Implicit memory

• Historical survey
• Carpenter (1874) noted the importance of
  autobiographical recognition or awareness in
  normal memory
• Neurology
• Korsakoff noted that amnesic patients were
  affected by previously experienced events even
  though they were consciously unaware of these
  events
• Claparede refusal of amnesic to shake hands after
  he had pricked her hand

5
Implicit memory

• Historical survey
• Neurology
• Schneider 1912 showed that amnesics required less
  information across learning trials to identify
  fragmented pictures

6
Implicit memory

• Historical survey
• Psychiatry
• Freud and Janet investigated patients suffering
  hysterical amnesia as a result of emotional
  trauma
• these patients could not explicitly remember the
  traumatic event, but their memories of these
  events were expressed indirectly (implicitly)
• Janet --hysterical amnesia consists of 1. the
  inability of a subject to evoke memories
  consciously and voluntarily and 2. Automatic,
  compelling, and untimely activation of these
  memories

7
Implicit memory

• Modern research on implicit memory
• effects of subliminally encoded stimuli
• several studies have shown that stimuli that are
  not represented in subjective awareness
  (consciously) are nevertheless processed to high
  levels by the perceptual system

8
Implicit memory

• e.g., Kunst-Wilson Zajonc (1980)
• presented geometric shapes for 1 ms claimed it
  was too brief a period of time to permit its
  perception subsequently tested recognition
  (forced choice) and preference (forced choice)
• Results RN was at chance Subjects preferred the
  previously presented geometric shape

9
Implicit memory

• e.g., Bargh Pietromonaco (1982)
• presented hostile words and then later had
  participants rate a target person
• results showed that explicit recognition memory
  of hostile words was at chance, although
  ratings of the target person were more negative
  than those who did not receive prior exposure
• e.g., divided attention study of Eich (1984)

10
Implicit memory

• e.g., divided attention study of Eich (1984)
• auditory divided attention task
• unattended channel -- presented homophones (e.g.,
  taxi fare)
• subsequently participants showed no explicit RN
  memory in yes/no task, but tended to spell
  homophones in biased direction compared to
  baseline performance

11
Implicit memory

• Learning and conditioning without awareness
• participants learn rules or contingencies without
  explicit memory for them
• this phenomenon was studied in multitrial
  learning experiments and in classical
  conditioning experiments

12
Implicit memory

• Implicit learning studies of Reber
• subjects were presented letter strings that were
  organized according to rules of an artificial
  grammar
• Reber reported that subjects could categorize
  these strings correctly even though they were
  unable to consciously aware of the rules

13
Implicit memory

• Repetition priming effects
• facilitation in processing of a stimulus as a
  function of recent prior exposure to the same
  stimulus
• note repetition priming has been observed under
  a wide variety of test conditions, none of which
  require explicit reference to a prior study
  episode
• lexical decision (word/nonword) -- DV latency
• word identification
• word stem or fragment completion (e.g., __
  ss__ss__)

14
Implicit memory

• Repetition priming effects
• 1. used to study nature of lexical representation
• e.g., studied the effects of auditory
  presentation on subsequent word identification
  and lexical decision tasks
• results showed little or no priming
• e.g., morphologically similar words (e.g., seen)
  facilitate priming of (sees), but visually
  similar words do not prime each other (e.g.,
  seen) versus (seed)

15
Implicit memory

• Repetition priming effects
• 2. used to study relation of implicit to explicit
  memory
• stimulated by studies of Warrington and
  Weiskrantz on amnesics
• this study showed that amnesics showed excellent
  retention when they were asked to complete
  three-letter stems of recently presented words
  even though their yes/no recognition memory was
  impaired

16
Implicit memory

• Repetition priming effects
• 2. used to study relation of implicit to explicit
  memory
• several studies have shown that variations in
  level or type of study processing have
  differential effects on priming versus
  remembering
• e.g., Jacoby Dallas (1981) showed that
  answering questions about the meaning of a target
  word improved yes/no recognition memory relative
  to answering questions about presence of a
  letter, but that word identification was
  unaffected

17
Implicit memory

• Repetition priming effects
• 2. used to study relation of implicit to explicit
  memory
• modality shift
• Jacoby Dallas (1981) showed that changing from
  auditory (at study) to visual (at test) severely
  attenuated priming effects as assessed by word
  identification, but had little effect on yes/no
  recognition performance

18
Implicit memory

• Repetition priming effects
• 2. used to study relation of implicit to explicit
  memory
• other factors that have been manipulated
• study-test delay--variable effects
• manipulations that affect retroactive and
  proactive interference (and hence explicit
  memory) have little effect on word-stem or word
  fragment completion

19
Implicit memory

• Repetition priming effects
• 2. used to study relation of implicit to explicit
  memory
• other factors that have been manipulated
• study-test delay--variable effects
• manipulations that affect retroactive and
  proactive interference (and hence explicit
  memory) have little effect on word-stem or word
  fragment completion

20
Implicit memory

• Aside
• A more recent study

21
Full vs. Divided Attention Effects on Implicit
and Explicit Retrieval of Evaluative Memories

• Norman W. Park, Zahra Hussain, Jill B. Rich

22
Evaluative Processes A Neuropsychological
Perspective

• Importance of evaluative processes for social
  interaction and problem solving
• Focal orbitofrontal brain damage (e.g., Damasio)
• Traumatic brain injury (e.g., Eslinger)
• Frontal variant of frontotemporal dementia (e.g.,
  Hodges)

23
Evaluative Processes A Neuropsychological
Perspective

• Proposed a dual process model of evaluative
  processing (Park et al.)
• Automatic and controlled processes
• Automatic process operates independently of
  controlled process
• Mediated by neurologically distinct regions

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Purpose of Current Study

• To investigate the underlying components
  associated with automatic and controlled
  evaluative processing of stimuli

25
Mere Exposure Effect

• Mere exposure effect (MEE)
• An increased evaluative preference for recently
  presented stimuli
• Robust phenomenon observed under a broad range of
  conditions
• Observed with novel but not familiar stimuli

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Mere Exposure Effect, cont.

• Mere exposure effect (MEE)
• Found under supraliminal and subliminal
  presentation conditions for novel stimuli
• Mediated by automatic processes involving a form
  of implicit memory

27
Explicit associative evaluative memory

• Evidence suggests that storing and retrieving
  this type of memory requires controlled processing

28
Experimental strategy

• Dividing attention should disrupt controlled
  evaluative processing more than automatic
  evaluative processing

29
Hypotheses

• Dividing attention should
• not influence the MEE (automatic)
• decrease explicit memory for evaluative
  information (controlled)
• Number of presentations should
• increase explicit memory performance
• no strong prediction for MEE

30
Hypotheses

• MEEs should occur with
• Positive and negative stimuli
• Novel stimuli (faces)
• MEEs should not occur with
• Familiar stimuli (words)

31
Participants

• 48 participants
• Ages 16-29
• Excluded if regularly plays an instrument
  requiring rapid finger movements

32
Materials

• 32 neutral-valence faces randomly paired with 32
  personality attributes (words)
• Half the attributes had positive valence (e.g.,
  honest, optimistic)
• Half had negative valence (e.g., malicious,
  jealous)

33
Design

• Between-subjects factors
• Attention (full, divided)
• Number of presentations (1, 3)
• Within-subjects factors
• Stimulus type (face, word)
• Valence (positive, negative)
• Test (likeability rating, recognition)
• Test item status (old, new)

34
Study Procedure

• Face (visual) word (oral) pairs presented at a
  5-second rate
• Divided attention condition
• Tapped fingers in order of ring, index, middle,
  little
• Full attention condition
• No tapping

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Test Procedure

• 3-minute delay after study
• Yes/no recognition memory and likeability ratings
  of faces words
• Test order of faces and words counterbalanced
  across participants

36
Results

• Face recognition performance
• Full gt divided attention
• 3 presentations gt 1 presentation

37
Face Recognition as a Function of Attention and
Number of Presentations
Hits Minus False Alarms
1 Presentation
3 Presentations
38
Results

• Likeability ratings of faces
• Previously viewed faces were preferred to new
  faces
• Full versus divided attention n.s.
• 1 versus 3 presentations n.s.

39

Full Attention Divided Attention 1
Pres 3 Pres 1 Pres 3 Pres
40
Results

• Likeability ratings of faces as a function of
  valence of studied attribute
• Paired t-tests were performed to determine
  whether the faces presented with positive
  attributes were rated differently from the faces
  paired with negative attributes
• Results show a valence effect only in the 3
  presentation full attention condition

41

Full Attention Divided Attention 1
Pres 3 Pres 1 Pres 3 Pres
42
Results

• Word attribute recognition performance
• Full gt divided attention
• 3 presentations gt 1 presentation
• Parallels face recognition results

43
Attribute Recognition as a Function of Attention
and Number of Presentations
Hits Minus False Alarms
1 Presentation
3 Presentations
44
Likeability ratingsof attributes

• Old (or previously viewed) attributes (both
  positive negative) rated more positively than
  unviewed (or new) attributes
• Positive valence items more likeable than
  negative items
• Full versus divided attention n.s.
• 1 versus 3 presentations n.s.

45
Preference Ratingsof Attributes
Positive Negative
46
Summary

• Dissociation between recognition memory and
  likeability ratings
• Recognition memory for faces and attributes
  higher for
• 3 gt 1 presentation
• Full gt divided attention
• MEE for faces and attributes unaffected by these
  2 factors

47
Summary

• MEE observed both when valence is positive and
  negative
• MEE observed both with novel stimuli (faces) and
  with familiar stimuli (words)

48
Discussion

• Results generally support the hypothesis that
  different processes mediate the evaluation or
  affective processing and memory for stimulus
  information
• Investigating the factor(s) responsible for the
  MEE with familiar stimuli

49
Implicit memory

• Implicit memory in amnesia
• produced by lesions to diencephalic and medial
  temporal lobe lesions
• pure amnesics have normal perceptual, linguistic,
  and intellectual functioning
• unable to remember explicitly recent events and
  new information
• however, amnesics have relatively normal skill
  learning and repetition priming, both forms of
  implicit memory

50
Implicit memory

• Implicit memory in amnesia
• skill learning Milner, Corkin and others have
  demonstrated that amnesics are able to learn
  pursuit motor learning and mirror tracing
• other skills that amnesics can acquire include
  rule learning, reading mirror-inverted script

51
Implicit memory

• Implicit memory in amnesiarepetition priming
• classic study Warrington Weiskrantz
• this study showed that amnesics showed excellent
  retention when they were asked to complete
  three-letter stems of recently presented words
  even though their yes/no recognition memory and
  free recall memory was impaired

52
Implicit memory

• instructions important Graf Mandler 1984
• showed that when amnesics are presented word
  stems as retrieval cues, and explicitly
  instructed to remember previously studied words
  -- they are impaired in their recall relative to
  normal controls
• in contrast levels of implicit memory
  performance-- complete stem with first word that
  comes to mind -- are equivalent for the two
  groups

53
Implicit memory

• Theoretical accounts
• threshold account
• 1 memory store account in which implicit memories
  are postulated to represent faint memory traces
• Evidence against statistical independence
  differential effects of certain encoding
  manipulations on explicit and implicit memories

54
Implicit memory

• Theoretical accounts
• activation account
• implicit memory effects are attributable to
  temporary activation of preexisting
  representations (e.g., logogens)

55
Implicit memory

• Theoretical accounts
• processing account
• explicit and implicit memories rely on newly
  established episodic representations difference
  between the two types of memories depends upon
  different processing demands placed by the two
  types of tests
• implicit memory is data driven, whereas explicit
  memory is conceptually driven conceptually
  driven processes guided by subject-driven
  activities, whereas data driven processes are
  driven by information present in the test stimuli

56
Implicit memory

• Theoretical accounts
• multiple memory system
• differences between implicit and explicit memory
  reflect differences between different memory
  systems
• e.g., Squire explicit memory is a form of
  declarative memory implicit memory is a form of
  procedural memory
• e.g., Tulving episodic memory mediates explicit
  memory implicit memory effects are mediated by
  semantic memory

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Implicit Memory
Explicit Memory
Priming
Nonassociative Learning
Neocortex
Reflex Pathways
Facts (Semantic Memory)
Events (Episodic Memory)
Skills and Habits
Simple Classical Conditioning
Striatum
Medial Temporal Lobe
Emotional Response
Skeletal Musculature
Amygdala
Cerebellum
Squire and Knowlton (1994) Squire (1987)
Declarative vs. procedural memory
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Implicit memory

• Strengths and weakness of Theoretical accounts
• Activation
• accounts for finding that priming does not depend
  upon elaborative processing
• amnesics show normal priming with pre-existing
  memory representations (e.g., familiar words,
  idioms) but not with unfamiliar materials

59
Implicit memory

• Strengths and weakness of Theoretical accounts
• Activation
• problems for activation
• finding that amnesics may be able to learn new
  factual information and new associations under
  some conditions

60
Implicit memory

• Strengths and weakness of Theoretical accounts
• processing account
• accounts for the associative effects, contextual
  sensitivity, and study-test interactions
• does not easily account for the importance of
  pre-existing representations in amnesics
• does not appear to account for the finding of a
  lack of conscious recollection of a prior
  experience at the time of test

61
Implicit memory

• Strengths and weakness of Theoretical accounts
• multiple memory account
• accounts most easily for the dissociation between
  amnesics and unimpaired findings
• amnesics can learn new factual information how
  is this possible given damaged declarative memory
  system?