IMPLICIT MEMORY: A “HIDDEN
WORLD?”
• Tasks and terms
– “indirect” (vs. direct) memory tests: no
memory judgments; assess effects of
prior exposure on
• Fragment completion
• Perceptual identification
• Repetition and “feature” priming
• Other decisions and actions
– Implicit (vs. explicit) memory: the
memory systems and/ or processes that
(largely) mediate performance in
indirect memory tests
• Contrast to:
– Incidental learning: no reference to
memory test during study
– Implicit learning: of patterns or
correlations without intent or awareness
Anecdotal Examples of Implicit
Memory
• Cases of “unconscious plagiarism”
– George Harrison and the Chiffons
– Freud’s “discovery” of universal
bisexuality, and Fliess’ reaction
• Use of expert knowledge
– Peter Bonyhard: helped IBM develop
mag-resist disk drives, barred from
working with competitor Seagate
• Implicit memory for traumatic events
– Amnesia for rape on a brick path, but
words “brick” and “path” come to mind
– Global amnesia, home is unfamiliar, but
“recently dreamed of that house”
• Implicit memory for words spoken
during anesthesia
– Kilstrohm & Schacter (1990)
THE SEARCH FOR
DISSOCIATIONS
• Stochastic
– Performance in IM and EM tasks given
same study is uncorrelated
• Functional
– Weak: variable X influences one kind of
test, (not) the other
• Levels of processing
• Modality
– Strong: variable X has opposite effects
on IM and EM tests
• Read versus generate (Jacoby 83)
• Population
– A functional dissociation where X is a
group factor (amnestics vs. controls)
• Reverse Association
– X affects A and B the same, Y has
opposite effects on A and B, in same
data set (Dunn & Kirsner, 1988)
A CAPSULE HISTORY of
IMPLICIT MEMORY
• Late 19th century
– Dissociations in the clinic (Dunn, 1845;
Claparede, 1889)
– Savings without explicit memory
(Ebbinghaus, 1885)
– Habit versus memory (James, 1890;
Bergson, 1911)
• 1970’s
– Controlled studies of priming in
amnestics
• HM can learn motor skills
• Amnestics show normal
fragment-completion priming
(Warrington & Weiskrantz, 1970)
recogn
fragment ID
Amnestics
.42
.46
Controls
.75
.45
• Demonstrations of implicit memory
in normals
– Jacoby & Dallas (1981):
• Depth affects recognition, not priming
• Modality affects priming, not recog
– Tulving, Schacter & Stark (1982):
• much less forgetting for implicit tasks
– Jacoby (1983):
• Opposite effects of context and
generation on implicit and explicit tasks
No context
XXX-COLD
context
HOT-COLD
generate
HOT-XXX
Jacoby, 1983
Probability correct
0.85
Identification
0.8
Recognition
0.75
0.7
0.65
0.6
0.55
0.5
no context
context
Study Task
generate
• Demonstrations of implicit memory
in normals (cont’d)
– Graf & Schacter (1987):
• Little interference with implicit
tasks
Word pairs studied (AB)
RI:
PI:
AB
AD
AD
AB
---
AB
AB
Control group learns CD
RI
PI
Ctl
Exp
Ctl
Exp
Cued recall
Fragment
.55
.40
.67
.45
Completion
.34
.32
.32
.35
THEORETICAL ACCOUNTS OF
IMPLICIT MEMORY
• The activation view (Graf & Mandler,
1987)
– IM as a subset of EM processes
• IM reflects activation of prior memories
• EM requires integration / elaboration
– Problems:
• Amnestics can learn new associations
• Priming can last for months
• The systems view (Tulving, 1985;
Schacter, 1987)
– IM based on procedural system, EM on
declarative system
• EM more advanced
• Explains neuroanatomic dissociations
– Problems:
• A system for every dissociation?
• Lack of consensus about criteria
• The processing view (Roediger,
Weldon & Challis, 1987)
– Transfer-appropriate memory tests
• IM : data-driven processing
• EM: conceptually-driven processing
– Dissociations can be TAP-based
(Blaxton, 1989)
“generate” (vs. read) gives better memory
for conceptually-driven tests
free recall (EM)
semantic cued recall (EM)
Jeopardy question-answers (IM)
and worse memory for data-driven tests
fragment completion (IM)
graphemically-cued recall (EM)
– Problems:
• Fuzzy bounds of processes
• Can become circular
• Doesn’t handle amnestic data well
THE PROCESS-DISSOCIATION
APPROACH (Jacoby, 1991)
• The problem of “process-impure
tests”
– Jacoby’s process-dissociation technique
– Assumes indendent concious (C) and
unconscious (U) contributions to memory
– To dissociate these:
two sets of items presented (e.g., some
read, some heard)
inclusion task: recall all
exclusion task: recall only heard items
p[corr]inclusion = p[C] + p[U] – p[U] x p[C]
= p[C] + p[U] x p[1-C]
p[corr]exclusion =
p[U] x p[1-C]
so: p[C] = inclusion – exclusion
then solve first equation for U
• Applying Process Dissociation: Jacoby,
Toth & Yonelinas (1993)
study presentation
Read
Incl Excl
Heard
Incl
Excl
Full attn
.61
.36
.47
.34
Divided
.46
.46
.42
.46
Estimated contributions of C and U to
memory:
C(conscious) U(automatic)
Full attn
.25
.47
Divided
.00
.46
Controversies about independence and
other assumptions