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

24. 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

26. 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

35. 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. Face Recognition as a Function of Attention and Number of Presentations Hits Minus False Alarms 1 Presentation 3 Presentations

37. Full Attention Divided Attention 1 Pres 3 Pres 1 Pres 3 Pres

38. Full Attention Divided Attention 1 Pres 3 Pres 1 Pres 3 Pres

39. Attribute Recognition as a Function of Attention and Number of Presentations Hits Minus False Alarms 1 Presentation 3 Presentations

40. Preference Ratingsof Attributes Positive Negative

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

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

43. 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

44. 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

45. 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

46. Implicit memory • Implicit memory in amnesia:repetition 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

47. 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

48. 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

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

50. 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