Implicit vs Explicit Memory

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Implicit Learning and Memory Overview
Implicit vs Explicit Memory

• Background
• Implicit Learning
• Implicit Memory
• Systems vs Processes
• How many types of implicit memory?

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Implicit vs Explicit Memory
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Background
Until mid 1980s - memory research concentrated on
memory system responsible for rapid, single-trial
learning, which allows a conscious recollection
of the learning experience. This memory system
appears to be particularly impaired in
amnesia. However, amnesic patients can perform
normally a variety of tasks which do not require
the capacity to recollect the learning
experience Increasing evidence that memory for
recently presented information could be
demonstrated in healthy control subjects in the
absence of conscious recollection This
dissociation led to the development of the
concept of implicit memory
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Background
A wide variety of dichotomies have been proposed
to account for the variety of LTM
phenomena Episodic vs Semantic Conscious vs
Unconscious Declarative vs Non-Declarative The
Implicit / Explicit distinction represents the
latest of these approaches to understanding the
nature of the LTS. Explicit memory revealed
when performance on a task requires conscious
recollection of previous experiences Implicit
memory revealed when performance on a task is
facilitated in the absence of conscious
recollection. Implicit memory research has been
dominant until the last few years
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Implicit Learning
There is no firm dividing line between implicit
memory and implicit learning (Seger
1994). learning complex information without
complete verbalisable knowledge of what is
learned Any skill which is acquired through
practice, and is not easily introspected and
expressed verbally could be termed implicit
knowledge - language, social skills, perceptual
skills, motor skills Implicit Memory usually
involves learning and testing same stimuli.
Implicit learning demonstrates transfer. Implicit
learning is not limited to perceptual / motor
skills Most research based on 2 paradigms 1.
Artificial Grammars 2. Control of complex systems
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Implicit Learning
Artificial Grammars
Subjects trained on grammatical sequences, then
presented with grammatical vs non-grammatical
sequences.
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Implicit Learning
Artificial Grammars Reber (1967) Group A Learn
grammatical letter sequences Group B Learn
random letter sequences Both groups then shown
44 letter sequences, 22 of which were gramatical,
22 of which were random (but used same
letters). Group A successfully categorised 79
of the words Group B were at chance Effect lasts
for years (Allen Reber, 1980) When questioned
about the nature of the grammar, subjects are
unable to report any knowledge of the rules (at
least early on). Many replications (but effects
tend to be smaller)
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How Implicit is Implicit Learning?
Are people really implicitly learning the
grammar? Some evidence that subjects may simply
be learning initial bigrams last letter. BUT
learning transfers to same grammar with different
letters (Matthews et al, 1989) Towards the end
of implicit learning expts, Ss can be capable of
articulating some useful information concerning
the rules learned. However, performance has
often improved before this point.
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Definitions
Implicit Learning The acquisition of complex
information (artificial grammars, production
rules motor skills etc). Explicit Memory -
requires conscious recollection of previous
experience Direct Free recall, cued recall,
recognition Implicit Memory - assessed without
reference to specific learning event indirect
performance facilitated in absence of conscious
recollection Memory research is in
terminological chaos. Implicit memory research
confused things even more It is often not clear
whether researchers are using the terms implicit
and explicit to refer to memory tests, the state
of awareness of the subject during task
performance, or theoretical constructs (e.g.
memory systems). These terms are essentially
descriptive rather than explanatory
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Implicit memory tests
Priming paradigms Subjects presented with
target words. Subsequent recognition phase
Targets and distractors. Fragment
Completion A--a--in Word Stem Completion Bri---
Implicit memory is evidenced when Ss complete or
identify more studied than non-studied
words. Perceptual Identification Tachistoscope
- RT Lexical Decision RT Degraded Word
Naming RT Implicit memory evidenced by faster
RTs for studied words
Paradigms used to test memory indirectly
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Not all implicit memory tests are verbal Closure
Pictures
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Evidence for Implicit / Explicit Distinction
1. Provides good explanation of amnesic
deficits Performance reflects the operation of
two separable memory systems Explicit memory
system is impaired in amnesia
2. Dissociations in normals Extensive evidence
that certain manipulations effect performance
when memory is tested one way, but not the other.
Typically, most manipulations influence
explicit, but not implicit memory
Paradigms used to test memory indirectly
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LOP Effects
Jacoby Dallas (1981) Subjects receive 60
words, 3 types of question Answer Y or
N Contains the letter L ? - WORLD Rhymes with
Drain? - TRAIN Is part of the nervous
system? - BRAIN
Test Standard Recognition (explicit) or
Perceptual Recognition (Implicit)
Standard LOP effect for recognition memory, but
not for perceptual recognition
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Generation effect
Memory for words generated at encoding is
superior to memory for words which were read
Electronic calculating device -
mpretcou Electronic calculating device - computer
Generation effect for Recognition, but not
perceptual recognition
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Forgetting
Tulving et al (1982)
Ss learn list of uncommon words (e.g.
Toboggan). Test standard recognition, fragment
completion (_O_O_GA_)
Repetition priming effect equal for recognised
and non recognised words Fragment completion
performance unchanged after 1w
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Theoretical Considerations
What is implicit memory? - Is it a system or a
process?
System accounts - favoured by neuropsychologists
observing preserved abilities in amnesics
Process accounts - favoured by experimental
psychologists working healthy subjects (often
using priming paradigms)
System accounts - Tulving Schacter (1994) -
Implicit memory reflects the operation of a
Perceptual Representational System
Process accounts - Roediger - Transfer
Appropriate Processing data driven vs
conceptually driven processes.
Baddeley - adequate explanation must account for
both the functional processes and the structural
system within which they operate.
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Theoretical Considerations
Systems accounts If Implicit and Explicit
memory effects represent the function of
separable memory systems, there should be no
correlations between measures of Implicit and
Explicit memory. Stochastic Independence (Sherry
Schacter) Tulving et al (1982)No correlation
between recognition and fragment completion. If
implicit memory is one system then there ought to
be correlations between different measures of
that systems performance. No correlations (refs)
so lots of different systems Quasi Memory (QM)
(Schacter, date) Perceptual Representation
System(s) (PRS) Date
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Process Accounts TAP
Process accountsAn attempt to stop the endless
proliferation of systems. Memory performance
depends on the extent to which the processes used
at the time of learning are the same as those
used at the time of testing c.f. Morris,
Bransford Franks (MMS lecture) Roediger and
colleagues developed the concept. Argued that
there are two broad types of cognitive
process 1. Data driven (perceptual) processes
The analysis of surface level features 2.
Conceptually driven processes The analysis of
meaning, or semantic information.
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TAP
According to this interpretation Data driven
(perceptual) processes underlie performance on
implicit tests Conceptually driven processes
underlie performance on explicit tests Avoiding
circularity Perceptual vs Conceptual
distinction can be operationally defined - e.g.
criteria are accepted. Read vs Generate
Manipulation Read gt Generate
Perceptual Generate gt Read Conceptual
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TAP
Not all Implicit memory tests are data driven,
and not all explicit memory tests are
conceptually driven. It is possible to construct
conceptual implicit tests, and perceptual
explicit tests According to TAP, dissociations
should occur between conceptual and perceptual
tests, regardless of their explicit-implicit
status. General Knowledge Test Ss view list of
unrelated words, told to remember them. Then
several intervening distractor tasks. Then
presented with a 100 Q general knowledge test.
50 answers were previously studied
words Conceptual Based on knowledge, not
perceptual properties Implicit Subjects not
consciously aware that their memory is being
tested
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TAP - Support
Blaxton, 1989 Four tests 1. Free Recall
(Explicit Conceptual) 2. General Knowledge
(Implicit Conceptual) 3. Graphemic cued recall
(Explicit Perceptual) 4. Fragment Completion
(Implicit Perceptual)
How do experimental manipulations dissociate
performance on these tasks? Systems 1 3 vs
24 Process 12 vs 34 Both Perceptual and
both conceptual tasks behaved in the same way.
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TAP - Problems
Neuropsychological data Key prediction of TAP
Amnesia reflects impaired conceptually driven
processes (Blaxton, 1992) Vaidya (1995) 1.
Perceptual Explicit (Word Fragment) 2. Perceptual
Implicit (Word Fragment) 3. Conceptual Explicit
(Word Associates) 4. Conceptual Implicit (Word
Associates) Amnesics should perform badly on
conceptual implicit and explicit tests (34), but
OK on perceptual implicit and explicit tests. In
fact, amnesic patients performed poorly on 13.
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Process pure tests?
How implicit are implicit memory tests?
It is very difficult to determine whether
performance on implicit memory tests was not
influenced by explicit memory E.g. it is
possible (probable?) that subjects are aware they
are filling in fragments with previously studied
words. Experimenters have attempted to address
this issue through questions at debriefing - not
satisfactory. Jacoby, Toth Yonelinas (1993)
developed Process Dissociation
Procedure Attempts to measure the relative
contributions of explicit (conscious) and
implicit (unconscious) processes on
recall. However, this procedure also makes some
questionable assumptions
Paradigms used to test memory indirectly
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PROBLEMS
Problems with implicit / explicit distinction
Terminology are researchers referring to a)
tasks? b) the subjects state of awareness during
tasks? c) theoretical constructs presumed to
underlie task performance?
Amnesics cannot do many things which rely on
implicit memory (e.g. learn their way around,
follow a plot etc)
Dichotomy implies two equivalent systems
Implicit memory may reflect the operation of
several distinct learning mechanism (Baddeley,
1997).
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Summary
Current memory theory has been described as
suffering from a taxonomic crisis, if not a
full-blown case of terminological chaos
Lockhart, 1989.
Roediger (1993). The female reproductive system
meets many of the requirements of a separable
memory system (e.g. it demonstrates priming)

• A vast range long term memory experiences /
  processes can be identified

• Various attempts have been made to classify
  these in some way

• Currently a broad consensus agree that a
  distinction can be made between recollective
  explicit memory and non-recollective implicit
  memory

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Implicit Learning
Controlling complex systems Task is to maintain
levels in one variable by manipulating another.
Berry Broadbent (1984) Transport system
(frequency of buses / cost of car parking) Sugar
production (amount of sugar / number of
workers) Mood induction Very different tasks,
but all governed by same equation Subjects
perform at about 80 after 60 trials. BUT no
correlations between task performance and
questionnaire performance ALSO performance
improves long before ability to instruct other
people in the task improves.