1. Implicit versus explicit memory: Definitions
implicit memory:
past experiences influence perceptions, thoughts and actions without awareness of person that any info from past is accessed
explicit memory:
conscious access to info from past (“I remember that..” )
-> involves conscious recollection
-> term generally used synonymously with episodic memory

2. Implicit memory: What studies in amnesia have told us
concept evolved out of neuropsychological research in patients suffering from amnesia; later studied in cognitive psychology, social psychology, developmental psychology etc.
first systematic study in densely amnesic patient H.M. (Brenda Milner, 1960s, in Montreal)
H.M.:
in 1953, bilateral surgical removal of medial temporal-lobes to stop his epileptic seizures, which couldn’t be treated with medication

3. Is normal implicit memory limited to motor learning in amnesia? No!
Warrington & Weiskrantz (1970) demonstrate that amnesic patients show preserved implicit memory on list learning with word stem completion task
Study: table, garden, telephone, lamp, umbrella etc.
Test: - Free Recall
- Yes/No recognition
- Word stem completion: tab____?
gar____?
(Instructions: think of any word that fits stem)
Finding: amnesic patients show memory deficits on first 2 tests but normal performance on word stem completion

4. Repetition priming in amnesia: Lack of retrieval intentionality is important
-> normal performance of patients on completion task but impaired cued recall and free recall
-> type of access (implicit vs explicit) to stored info critical

5. Can repetition priming also be shown to be different from explicit memory in normal subjects?
Tulving, Schacter, & Stark (1982):
fragment completion task
study: incidental learning with semantic decisions; judge words in terms of animacy
(e.g. twilight, assassin, dinosaur, mystery)
test: complete fragments with first word that comes to mind
ch_ _nk
o_t__us
_ssa__in
repetition priming: more completions of studied than non-studied words

6. Repetition priming in normal subjects
Tulving, Schacter, & Stark (1982):
+ repetition priming effects long-lasting (no ‘forgetting’ over a week or more)
+ by contrast, recognition memory for previously studied words shows some forgetting
->> even in normals implicit memory can be distinguished from explicit/episodic memory

7. Does repetition priming require attention at time of encoding?
informal (unethical!) observation with ‘mock crisis’ in 1960s:
faked crisis during surgery causes subsequent agitation in patients recovering from surgery, without their knowing why
systematic (ethical!) studies show that encoding under anesthesia produces repetition priming when patients are tested after surgery on word-fragment completion task
-> no allocation of attention required at encoding

8. Is repetition priming linked to semantic memory?
Does it benefit from semantic encoding ?
(LoP study; Graf & Mandler)
study:
- semantic decisions (animate /inanimate)
- physical decisions
(# of capital letters)
test:
cued recall
fragment completion
Finding: no LoP effect on completion task
-> not likely that semantic memory involved

9. Is repetition priming a perceptual type of memory?
two important findings:
reductions in repetition priming effects with
+ changes in modality between study and test
(e.g. encoding of words in auditory modality
word-fragment completion test in visual modality)
+ changes in perceptual characteristics of words between study and test (e.g. font, uppercase/lowercase)…
-> suggests that priming reflects a perceptual type of memory; fits with finding of no LoP effect
best term to capture phenomenon: perceptual priming

10. If it is perceptual, can priming be observed in other sensory modalities?
yes; evidence for perceptual priming on auditory word-stem completion task (after incidental encoding in auditory modality)
-> priming not limited to visual modality

11. Can perceptual priming be observed with non-verbal stimuli?
experiments with possible and impossible objects by Schacter & Cooper (early 90s)
Study: judge whether object faces left or right
Test: object decision task with 100 ms exposure
with studied and non-studied objects
Finding: more accurate performance with previously studied objects (priming)

12. Is perceptual priming on object decision task an expression of semantic memory?
Schacter & Cooper (early 90s)
comparison of encoding effects for recognition memory (explicit) and perceptual priming on object decision task (implicit)
+ physical vs semantic judgements at encoding
(left-right facing vs what real object does it remind you of)
-> semantic encoding only improves recognition
-> finding suggests that priming perceptual in nature

13. Interpretation of perceptual priming: Perceptual representation systems (PRS)
theory proposed by Schacter & Tulving:
+ perceptual representation systems: not dedicated memory systems but perceptual systems that keep memory as by-product of perceptual analysis
analogy: hot-tube effect with stove
+ memory representations in PRS operate implicitly
(no conscious recollection possible)

14. Interpretation of perceptual priming: Perceptual representation systems (PRS)
Schacter & Tulving:
visual representation system for words
-> representation: visual word forms
visual representation system for objects
-> representation: structural descriptions of objects
auditory representation for words
-> representation: auditory word forms (phonology)
perceptual representation systems rely on brain structures that perform perceptual analyses
e.g. visual representation systems localized in visual cortex

15. Functional neuroimaging evidence for perceptual priming in PRS: reductions in brain activation
C: unprimed objects
D: primed objects
activity reductions in visual cortex for primed objects
effect at behavioural level:
priming = facilitated performance

16. Problems for studying perceptual priming as type of implicit memory
typical set-up of priming study
study: incidental encoding of word list (table, garden, telephone, umbrella etc.)
priming test: word stem completion
complete word stem with first word that comes to mind
rea___??
gar___??
net___??

17. Problems for studying perceptual priming as type of implicit memory
does performance on priming task always reflect implicit memory?
no! -> problem of ‘explicit contamination’
e.g. subjects may rely on conscious recollection to perform stem completion task even when no explicit memory instructions are given
-> presumed implicit memory task may not always measure concept of implicit memory
L. Jacoby’s approach to purify measures of implicit memory:
process dissociation procedure (method of opposition)

18. Process dissociation procedure to purify measures of implicit memory
experiment by Jacoby et al. with word-stem completion task
Study: incidental encoding of words under full or divided attention
Test: word-stem completion task under Inclusion or Exclusion instructions
Jacoby’s terminology:
implicit memory = automaticity
explicit memory = recollection

19. Process dissociation procedure
inclusion condition:
try to generate a word that begins with stem; simply take first word that comes to mind; you can take one presented earlier
-> implicit and explicit memory work in same direction
exclusion condition:
try to complete stem but avoid completions of words presented earlier
-> implicit and explicit memory work in opposite direction
Inclusion = e + i (1 - e) -> formula allow to get Exclusion = i (1- e) purified estimates for implicit (i) and explicit
e = Inclusion – Exclusion (e) memory contributions
i = Exclusion/(1-R)

20. Process dissociation procedure
finding:
attention only affects estimates of explicit not of implicit memory
-> procedure offers powerful way to study implicit and explicit memory processes separately
explicit
implicit

21. Types of implicit memory other than perceptual priming
motor skill learning (e.g. mirror drawing task)
+ normal in amnesic patient H.M.
-> does not rely on medial temporal lobe structure
+ patients with Huntington’s disease (neurological disease of motor system; brain damage in basal ganglia) show impaired motor skill learning but normal perceptual priming
-> does not rely on PRS either
-> type of implicit memory that is different from perceptual priming

22. Types of implicit memory other than perceptual priming: Conceptual priming
can be shown with category instance generation task
study: incidental encoding of words
(e.g., cycle, tree, mail, elephant, tulip etc.)
test: name as many members of the following category in 1 min
e.g., flowers - ?? (note: no perceptual cue from study phase)
priming effect: previously studied category members more likely generated than others
conceptual priming typically normal in amnesic patients

23. Types of implicit memory other than perceptual priming
is conceptual priming different from perceptual priming?
yes!!
+ it benefits from semantic encoding (LoP effect)
+ not affected by switch in perceptual modality between study and test
+ dissociation in patients with Alzheimer’s disease:
normal perceptual priming but impaired conceptual priming
-> suggests that they rely on different brain structures
-> conceptual priming not based on PRS;
instead builds on semantic memory

24. Are they really different types of implicit memory?
perceptual priming
conceptual priming
motor skill learning
-> research suggests that each of them relies on different brain structures and has different functional characteristics (e.g. modality, LoP effect, forgetting curve)
BUT commonality:
implicit access to information from past
-> unconscious form of memory!!

25. Does implicit memory occur in everyday life?
yes, most certainly
BUT difficult to grasp given its unconscious nature
applied research shows:
+ mere exposure to advertisements influences subsequent affective judgments of these ads (attitudes), although subjects don’t remember seeing them (Perfect & Askew, 1994)
Schacter’s examples:
+ unintentional plagiarism (conceptual priming?)
e.g. George Harrison’s ‘My sweet lord’
+ motor skills, e.g. in sports and music

26. Amnesia / Amnesic Syndrome: selective LTM impairments caused by neurological condition
retrograde
amnesia
anterograde
amnesia
remote
past
recent
past
time
onset
of neurological
condition

27. Neurological conditions that can produce amnesia
temporal lobe resection (neurosurgery)
traumatic closed head injury (massive blow to head)
herpes simplex encephalitis (viral infection)
ischemia (vascular problem; interruption of blood flow to brain)
stroke, ruptured aneurysm (bleeding from blood vessel)
Korsakoff’s syndrome (Vitamin B1 deficiency)
Alzheimer’s disease (type of dementia)
Milder, more limited memory impairments also with:
epilepsy (brain seizures)
brain tumors
chronic alcoholism

28. Neuroanatomical basis of anterograde amnesia: Where is brain damage typically localized?

29. Selective memory impairments of H. M
Selective memory impairments of H.M. and other patients suffering from anterograde amnesia
in neuropsychological testing:
+ normal IQ
+ normal perceptual and language functions
+ severe deficits on episodic memory tasks; not specific to particular info / material:
e.g. problems with
- learning of word lists
- recognition of faces and other non verbal info (scenes, houses etc.)

30. How can anterograde amnesia be explained
How can anterograde amnesia be explained? What is the nature of the memory impairment?
general findings in amnesic patients:
+ normal STM capacity on digit-span task
+ normal forgetting curve on Brown-Peterson task
+ normal recency effect in serial position curve

31. Additional evidence showing that memory deficit is specific to LTM in amnesic patients:
lists larger than STM span extremely difficult to learn for patients (Drachman & Arbit, 1966)

32. How can anterograde amnesia be explained
How can anterograde amnesia be explained? What is the nature of the memory impairment?
STM / WM intact
-> problem in long-term memory (LTM)
but does it affect all aspects of LTM?

33. Motor-skill learning: a type of implicit memory that is normal in H.M.
mirror tracing task: builds on procedural memory for skills
improvement in tracing performance with practice but no recollection of previous training sessions
(i.e. episodes)
-> suggests that H.M. retains some info over long-term and can access it implicitly

34. Normal perceptual priming on word-stem completion task in anterograde amnesia
-> normal performance of patients on completion task but impaired cued recall and free recall
-> type of access (implicit vs explicit) to stored info critical

35. How can anterograde amnesia be explained
How can anterograde amnesia be explained? What is the nature of the memory impairment?
STM / WM intact
-> problem in long-term memory (LTM)
implicit memory intact
+ perceptual priming
+ conceptual priming
+ motor-skill learning procedural memory
(learning how to)
-> problem in explicit memory (consciously processed info in LTM)