Memory experiments of Ebbinghaus Examination of forgetting curve with savings method

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

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

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

4. 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

5. 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

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

7. Further research on chunking • optimal chunks can be unique for different individuals (e.g. running times; dates) • learning of new chunking methods possible but labor-intensive (e.g. digit-letter mapping system) • when chunking leads to larger absolute number of digits being retained, capacity still remains unchanged: -> 7+ 2 chunks -> change in coding of info instead

8. 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

9. 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”

10. 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)

11. 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??

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

13. Forgetting mechanisms in STM vs LTM • retroactive interference on paired-associate learning task: What was the missing 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 • application in everyday life: previous postal code after move

14. 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 - different from interference on LTM tasks -> numbers in distractor task known to produce minimal interference for letters -> forgetting observed on Brown-Peterson task reflects trace decay - interpretation later challenged by Keppel & Underwood

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

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

17. Interpreting effect of presentation rate and delay in Glanzer & Cunitz’s experiment • Presentation rate: • more rehearsal allows for better transfer 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)

18. Other evidence in support of two-store interpretation of serial position curve • detrimental effect of old age only on primacy portion • beneficial effect of word familiarity only on primacy portion • (more familiar words recalled better than less familiar ones)

19. 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

20. What makes a list difficult for LTM (Baddeley, 1966)? detrimental effect of semantic but not acoustic similarity on learning of long word lists

21. Interpretation of ‘difficulty findings’ in Baddeley’s experiment • detrimental effect of acoustic similarityon recall of brief lists suggests that info is coded phonologically (in terms of sound) in STM • detrimental effect of semantic similarity on recall of longer lists suggests that info is coded semantically (in terms of meaning) in LTM

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

23. What kind of memory is impaired in neurological patients suffering from amnesia? • amnesia can occur as result of sudden brain injury (e.g car accident) or stroke • - patients do not remember anything from hours / days before incident • - patients have difficulty keeping track of daily events • - patients have difficulty learning names of new people (e.g. physicians and nurses) • - patients have difficulty learning way around in new environment (e.g. hospital) • amnesic patients have memory deficits but otherwise normal intelligence -> can be tested on experimental tasks used in memory research • critical question: does amnesia affect STM, LTM or both?

24. 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 • could suggest that only LTM affected by amnesia

25. Serial position curve in amnesic patients (Baddeley & Warrington, 1970) • most aspects of list learning impaired but recency portion in immediate recall normal in patients • -> further support for idea that amnesia affects LTM but not STM

26. 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

27. Can other types of brain damage lead to impaired STM? • patient K.F. studied by Shallice and Warrington (1970) • + brain damage different from that in amnesic patients • + immediate memory span limited to 2-3 digits • + poor performance on Brown-Peterson task, especially with auditory presentations • + normal performance on list learning tasks with long lists • + normal primacy but impaired recency effect • -> patient’s memory deficits seem to be limited to STM; LTM unaffected by damage

28. What do patient studies tell us about distinction between STM and LTM? • observed pattern of deficits across studies: • + one type of neurological condition leads to impairments in LTM but not STM • + other type of neurological condition leads to impairments in STM but not LTM • -> evidence for double-dissociation of STM and LTM deficits • -> suggests that LTM and STM require normal functioning of different brain structures • -> suggest that LTM and STM have distinct neural basis