A pioneer of the scientific study of memory: Hermann Ebbinghaus (1850 – 1909)

1. A pioneer of the scientific study of memory:Hermann Ebbinghaus(1850 – 1909) • worked as philosopher at university in Berlin • inspired by lawfulness of relation between physical properties of perceptual stimuli and psychological sensations discovered in field of psychophysics e.g. Fechner’s law; Weber’s law

2. Classic finding in psychophysics: Weber’s law standard line just-noticeably-longer line

3. A pioneer of the scientific study of memory:Hermann Ebbinghaus (1850 – 1909) • performed experiments on himself published in classic volume entitled: ‘Über das Gedächtnis’ (1885) • famous because: - pioneer of empirical approach - inventiveness as experimenter

4. Memory experiments by Ebbinghaus • new:systematic and controlled study of memory in laboratory e.g. - created new stimulus material - applied scientific accuracy (use of metronome) - established method to quantify memory performance and describe regularities

5. Memory experiments of Ebbinghaus:how to investigate retention of newly learnt material • invented lists of 16 nonsense syllables to minimize influence of learner’s history goal: study memory in ‘pure’ form • introduced criterion for successful learning (2 errorless recitations) • introduced savings method to measure retention/forgetting of lists

6. Memory experiments of Ebbinghaus:Example of memory task • memorize the following (shortened) list: falem zeb xalvo monul rull namak

7. Memory experiments of Ebbinghaus:Examination of forgetting curve with savings method • calculation of savings scores to measure performance • finding: most forgetting occursright after learning -> approx. 50% in first 40 min -> relationship between delay andforgettingnot linear

8. Memory experiments of EbbinghausOther important findings • list-length effect: amount of information and ease of learning not related in linear one-to-one fashion; disproportionate increase in difficulty with more than 7 syllables • beneficial effects of distributed practice for repetitions

9. Memory research of EbbinghausWhy is it such a major contribution? • discovery of important regularities (basic findings) • memory can be studied empirically with experiments • mental phenomena can be studied even if they are not linked directly to physical world via perceptual organs

10. Memory research of EbbinghausWhat was missing? • research criticized as atheoretical • but: emphasis on observations rather than theories typical for early research in new field

11. The Ebbinghaus Legacy:Verbal-learning research 1950s – 1970s • behaviourist tradition (S-R / S-S associations) • mind as black box • systematic study of factors affecting verbal learning: e.g. numbers of repetitions, presentation time; word frequency • later replaced by information-processing approach: growing emphasis on mental representations

12. Richard Semon (1859 – 1918): An early memory theorist • work strongly influenced by evolutionary biology (Darwin) • interest in commonality between heredity and memory: aspect of biological tissue that allows effects of experience to be preserved over time • three stages of memory (new terms invented) Engraphy – acquisition of new information Engram – enduring change in nervous system that allows for retention Ecphory – recovery of stored information

13. Richard Semon (1859 – 1918): An early memory theorist • concept of ‘engram’ motivated much research on brain basis of memory in 20th century: What are the manifestations of memory traces in the brain? • concept of ‘ecphory’ strongly influenced cognitive psychology of memory in 1970s (Tulving): How can a dormant memory trace be awoken? -> emphasis on processes at time of retrieval (recovery) of info from memory -> emphasis on presence of suitable retrieval cues

14. Information-processing approach to memory(starting 1960s) • motivated by emerging of computers and computer science as scientific discipline • human mind can be understood with computer metaphor: e.g. storage of information in different memory buffers RAM vs hard-disk <-> STM vs LTM • central importance of information and mental representations (mind not a black box) • focus on cognitive processes that deal with (e.g. create, access, compare) mental representations

15. correct Information-processing approach to memory:A practical example

16. Encoding Retrieval time Information-processing approach to memory:Basic framework • 3 stages of processing for manipulation of mental representations: Encoding (acquisition of info) Storage (retention of info) Retrieval (recovery of info)

17. Information-processing approach to memory:Typical research questions • do we store different types of memory representations? Are they retained equally well? e.g. ‘bear’

18. Information-processing approach to memory:Typical research questions (cont’d) • do we need attentional resources to encode new information into memory? e.g. can be studied through examination of influence of distraction • can information in memory influence our thoughts and actions unconsciously? e.g. can be studied in patients under anesthesia

19. Information-processing approach to memory:Application to Ebbinghaus’ research • what were the syllables you memorized in the example I gave earlier?

20. Information-processing approach to memory:Application to Ebbinghaus’ research • which of the following syllables was on the list? halek or xalvo -> forgetting curves will vary depending on whether syllables need to be recalled or recognized -> more detailed analysis of cognitive processes required to understand regularities in forgetting

21. Information-processing approach to memory:Application to Ebbinghaus’ research • e.g. ‘zeb’ may or may not make you think of ‘zebra’ at encoding -> consequences for subsequent remembering -> even learning of simple stimuli such as non-sense syllables is affected by variations in cognitive processing and pre-existing knowledge -> memory can’t be investigated in pure form

22. Cognitive-neuroscience approach to memory • multidisciplinary approach (psychology, computer science, neurology, radiology) • emphasis on relationship between behaviour, cognition, and the brain • central question:how dos the brain allow humans to learn and remember? • general idea: to understand the organization of memory (e.g. how many different types?) we should focus on neurological and cognitive aspects

23. Cognitive-neuroscience approach to memory:Different types of investigation • lesion studies in neurological patients examination of effects of different types of brain damage on memory processing • functional neuroimaging examination of brain activity in healthy individuals while they perform memory tasks • computational modeling testing of quantitative memory theories with computer models that incorporate a brain-like organization (neural networks; connectionist models)

24. Cognitive-neuroscience approach to memory:Example of functional neuroimaging study • do different parts of the brain become active when we try to remember pictures as compared to words? pictures words

25. Memory experiments of EbbinghausExamination of forgetting curve with savings method • most forgetting happens immediately after learning -> approx. 50% in first 40 min

26. Forgetting on Brown-Peterson taskwith consonant trigrams • Repeat ‘HLM’ • 2. Distractor task: Count in 3s from 492 • 3. What were the letters? • many trials with different delays • after 6 sec only 40 % correct recall

27. Forgetting on Brown-Peterson taskwith consonant trigrams • findings suggest short-lived memory component different from type of memory studied by Ebbinghaus

28. Something special about short lists • Ebbinghaus: lists with up to 7 nonsense syllables are forgotten at different rate than lists with more items • G. Miller (1956): immediate memory span ‘Magical number seven, plus or minus two’ + holds for digits, letters, words (digit span, letter span, word span) -> suggests that short lived memory component has limited capacity

29. Further examination of immediate memory span • integration of information through chunking possible e.g. letters in meaningful word letters in acronyms (USA, IBM) area code in phone number • chunks are basic storage units in short-lived memory component

30. Chunking produces similar forgetting curve on Brown-Peterson task with words and trigrams

31. Consequences of findings with Brown-Peterson task and with memory span in 1960s • new notion: memory is not unitary • there may be at least two separate stores that work with different cognitive mechanisms • they seem to differ in terms of forgetting rates and capacity -> longer lasting component may not have any capacity limitations e.g. + Ebbinghaus could remember lists of 40 and more nonsense syllables +everyday observations suggest that memory capacity for life events unlimited

32. W. James: Primary vs secondary memory • Primary memory: “ it was never lost; its date was never cut off in consciousness from that of the immediately present moment; in fact, it comes to us as belonging to the rear-ward portion of the present space of time, and not the genuine past” -> extended present • Secondary memory: “ the knowledge of a former state of mind after it has already once dropped from consciousness; or rather it is the knowledge of an event, or fact, of which we have not been thinking, with the additional consciousness that we have thought or experienced it before”

33. Different proposals for two-store models • W. James (late 1800s): primary memory vs secondary memory ‘still in consciousness’ vs ‘lost from consciousness’ • Atkinson & Shiffrin (1968): short-term memory (STM) vs long-term memory (LTM) • Baddeley (1980s) further theoretical development of concept of STM -> renamed: working memory (WM)

34. Consequences of findings with Brown-Peterson task and with memory span in 1960s • controversy over need to postulate two stores • philosophy-of-science argument relevant: more parsimonious theory better than more complicated one if it can explain the same findings (principle of Ocham’s razor) -> is there sufficient number of critical findings that single-store theory cannot explain?

35. Forgetting mechanisms in STM vs LTM • typical explanation of forgetting on list-learning tasks (à la Ebbinghaus) and others task studied in verbal-learning research: interference e.g. paired-associate learning task First list Second list car – ball car – fridge tree – screen tree – foot table – paper table – ocean … … door – sports door – hair

36. Forgetting mechanisms in STM vs LTM • retroactive interference on paired-associate learning task: What was linked word from first list?tree – ? door – ? -> learning of second list impairs recall of first list • interpretation in behaviourist learning theory: associations between pairs in first list weakened through learning of second list • application in everyday life: previous postal code after move

37. Forgetting mechanisms in STM vs LTM • suggestion for forgetting on Brown-Peterson task: trace decay (fading) - occurs as soon as stimulus absent - can be prevented through active rehearsal - thought to be different from interference-related forgetting onLTM tasks (notion later challenged)

38. Other evidence to support distinction between STM and LTM:Serial-position curve in free recall task recency effect primacy effect

39. Effects of presentation rate and delay on serial position curve (Glanzer & Cunitz, 1966)

40. Interpreting effect of presentation rate and delay in Glanzer & Cunitz’s experiment • presentation rate: • more rehearsal allows for better transfer of info from STM into LTM in primacy portion • delay: • trace-decay in STM eliminates recency • -> different experimental manipulations have different effects on recency and primacy portion of curve • -> suggests that primacy and recency effects reflect operation of different stores (LTM, STM)

41. What makes a list difficult for STM (Baddeley, 1966)? unrelated semantically similar acoustically similar detrimental effect of acoustic but not semantic similarity on immediate recall of short word lists

42. Interpretation of ‘difficulty findings’ in Baddeley’s STM experiment • detrimental effect of acoustic similarityon recall of brief lists suggests that info is coded phonologically (in terms of sound) in STM

43. Evidence suggesting semantic code for LTM • prose passage experiment by Sachs (1967) • e.g. sentence heard as part of story: • ‘she watched the kids on their way home’ • LTM test after 20 min delay • Was the following sentence part of the story? • - she watched the birds on their way home • (no; easy; few errors) • - the kids were watched by her on their way home • (no; difficult; many errors) • - she observed the kids on their way home • (no; difficult; many errors) -> good recognition of semantic but poor recognition of verbatim information

44. Interpretation of findings on retention of verbatim info in LTM • poor recognition of verbatim info with good recognition of semantic info suggests that info is coded semantically (in terms of meaning) in LTM

45. What kind of memory is impaired in neurological patients suffering from amnesia? • amnesia can occur as result of sudden brain damage • (e.g car accident, stroke) • - patients do not remember anything from time since injury • - patients have difficulty keeping track of daily events • - patients have difficulty learning names of new people (e.g. physicians and nurses on ward) • - patients have difficulty learning way around in new environment (e.g. hospital) • critical question: does amnesia affect STM, LTM or both?

46. What kind of memory is impaired in neurological patients suffering from amnesia? • general findings in amnesic patients: • + normal STM capacity on digit-span task • + normal forgetting curve on Brown-Peterson task • + normal receny effect on list learning task • suggests that LTM but not STM is affected by amnesia

47. Additional evidence showing that memory deficit is specific to LTM in amnesia:Findings with ‘span + 1’ task(Drachman & Arbit, 1966) lists larger than STM span extremely difficult to learn for patients

48. What do patient studies tell us about distinction between STM and LTM? • observed pattern of deficits across studies: • + one type of brain damage leads to impairments in LTM but not STM • + other type of brain damage leads to impairments in STM but not LTM • -> suggests that LTM and STM rely on proper functioning of different brain structures • -> suggest that LTM and STM have distinct neural basis

49. Characteristics of two separate memory stores (as widely accepted in 1970s) Note: concept of STM different from use of term in everyday life

50. Atkinson & Shiffrin’s modal memory model