PSYc20007 Basics of Memory: Causes of Forgetting PDF

PSYC20007 Basics of Memory: Causes of Forgetting Adam Osth  Outline for the coming weeks Lecture 1: Basics of memory/forgetting – What leads to better memory? What causes us to forget things? Lecture 2: False memory – Why do we remember things incorrectly? Lecture...

PSYC20007 Basics of Memory: Causes of Forgetting Adam Osth  Outline for the coming weeks Lecture 1: Basics of memory/forgetting – What leads to better memory? What causes us to forget things? Lecture 2: False memory – Why do we remember things incorrectly? Lecture 3: Language – How do we study language in the lab? How is memory for language different than memory for other things? Lecture 4: Judgment and decision making – How do we make decisions? How are they influenced by what we remember?  In the beginning! Hermann Ebbinghaus – First experimental psychologist of memory – Had subjects study list of nonsense trigrams: consonant-vowel- consonant E.g., ”teg”, “raz”, “fip”  In the beginning! – Many findings from Ebbinghaus’s experiments Spacing effects: repetitions more effective if you space them out over time rather than mass them consecutively – Presenting A-B-C-A-B-C-A-B-C is more effective for learning than A-A-A-B-B-B-C- C-C – Practicing piano one hour each day is better than seven hours on one day List length effects: Worse memory when you study longer lists versus shorter lists Forgetting curve: the shape of how memory declines over time The Forgetting Curve  Ebbinghaus’s contributions Ebbinghaus established the experimental tradition of memory – Presenting randomized lists of “non-meaningful” stimuli to participants under controlled conditions – Control for exposure duration, retention interval, etc. Can more precisely understand what leads to better/worse memory – Various reasons why something is not remembered! Lack of attention to the stimulus when learning, inability to locate the memory at retrieval, etc. Many phenomena he discovered have replicated and are still of focus today The Laws of Memory  What is a law? Invariance or regularity in data They do exist in psychology! – The law of practice Performance improves as a logarithmic function of practice – The Yerkes-Dodson law Performance is an inverted-U shaped function of arousal Theories and laws are not the same thing! – A law states a regularity in data or the natural world – A theory provides an explanatory framework for phenomena (and sometimes laws) in the natural world  The Laws of Memory Kahana, Diamond, and Aka (2023) recently collected a number of laws on what affects memory Law of Recency – Recent information is almost always better remembered than older information – The recency function is non-linear: older information decays at a slower rate than newer information  Law of Recency Recency Non-linear advantages forgetting: observed at short older information time scales- decays at a better slower rate performance with shorter delays  Law of Recency Recency advantages observed at long time scales too!  The Laws of Memory The Law of Primacy – Better memory for items that were start of a sequence – Most commonly observed in lists, but can also be observed during event changes Murdock and Carey (1972): changes in modality (from auditory to visual) induce primacy effects at the change  The Law of Repetition Memories improve with repetition …but some repetitions help more than others! – Memory improves the most with spaced repetition Massed repetition is when repetitions occur consecutively (e.g., A-A-A-B-B-B-C-C-C) Spacing the repetitions out over items almost always results in better memory (e.g., A-B-C-A-B-C-A-B-C)  The Law of Repetition The x-axis refers to the number of items between the repetition Data from Glenberg (1976)  The Law of Repetition An implication of the spacing effect – Better to practice piano one hour a day then seven hours on one day – Better to study a bit each day then cram before the test …then why do I do well on the test when I cram? – Peterson paradox: spaced repetitions perform WORSE than massed repetitions for a short delay – …but perform better after a long delay!  The Law of Repetition Slightly better performance for massed items with a very short Massive delay advantage for spaced condition in the longer delay condition Spaced repetition s promote better long Data from Peterson et al. term (1972) learning!  The Law of Repetition Testing improves memory above and beyond re- learning – E.g., if you study and test on a set of items, you see better memory than if you studied the same material twice – Similar to spacing effects, these effects are the strongest after a delay Data from Sometimes there is a benefit Roediger and to repeated study at very Karpicke (2006) short delays  The science of how repetitions benefit memory has been found to replicate with classroom materials (Roediger & Karpicke, 2006) – The benefits of spacing and testing have been used as recommendations to both educators and students to improve memory Does a *negative* occurrence of any of these phenomena refute the law? Even in physics, no law is consistently observed in each and every case – Newton’s laws (classical mechanics) break down at the quantum level – Some laws are not observed because of some other influence The fact that planes or leaves float in the air doesn’t violate the law of gravity Forgetting  How can forgetting occur? Forgetting can be due to either encoding failure or retrieval failure – Encoding failure: you never learned what you need to remember in the first place E.g., someone tells you you need to pick up groceries while you’re texting someone else – Retrieval failure: you initially learned the material, but you were unable to retrieve it at a later time E.g., you might have trouble remembering an old password or an old phone number, but you definitely learned it initially  But why does forgetting occur? Four possible theories of retrieval failure: – Decay theory – Interference theory – Consolidation theory – Inhibition theory  Decay Theory Stored memories fade over time – Brown-Peterson paradigm: Subjects learn trigram, count backwards by seven for a period of time Counting backwards by 7 was to prevent participants from rehearsing the material – Rehearsal can keep memories active and overcome the influence of decay Almost no memory after ~20 seconds  Interference Theory Started with John McGeoch (1932) – claimed that decay theory is conceptually flawed – Iron rusts over time, yet it is not time itself that degrades it – With memory, forgetting occurs because over time there is more interfering mental activity Specifically, forgetting occurs because there is competition between things we are attempting to remember – There is greater competition as we learn more!  Interference Theory Why is there competition? – When we learn, we associate things together E.g., associating a name to a face! – When presented with one of those things in isolation (the cue), we can recall the associate When we see someone’s face, we can remember their name When presented with someone’s name, we can remember their face – The more associations there are, the harder it is to remember things!  SHAME X-MEN FIRST CLASS Michael PROMETHEU Fassbender S When we learn, we form associations between what we are experiencing – these can vary in strength  Memory prompt: What movies was Michael Fassbender in? We are most likely to remember the movie that has the strongest Michael Fassbender association (e.g., X-Men First Class)  ADAPTATION MARVIN’S ROOM LITTLE WOMEN MANHATTAN THE FANTASTIC MR Meryl Streep FOX MAMMA MIA THE RIVER WILD  When there are many more associations, it becomes harder to remember a particular associate! e.g., a list length effect Meryl Streep  Interference and lockdown! Interference theory can even explain why lockdowns impair memory – We are associating what we learn to the same cues! E.g., our house, our surroundings – This makes it harder to remember particular things – https:// theconversation.com /how-the-groundhog-day- grind-of-lockdown-scrambl es-your-memory-and-sens  What is interference? More associations to a cue, the harder it is to retrieve the correct memory – Inability to retrieve new associates can be because of interference from older ones This is proactive interference – Inability to retrieve old associates can be because of interference from newer ones This is retroactive interference – Ideas about interference were directly lifted from animal learning (e.g., classical and operant conditioning)  Interference in Lab Studies AB-CD paradigm – Two lists of items with no overlapping associations – During the memory test, subjects presented with a cue (e.g., “dog” or “hope”) and asked to retrieve the associate List 1 List 2 dog – king car - bottle plant – butter hope - sock box - rug fire - fence  Interference in Lab Studies AB-AC paradigm – Second list shares the same cues as the first – Worse performance on List 2 items compared to the AB-CD condition (this is proactive interference) List 2 cues can produce either List 2 targets List 1 1 targets or List List 2 dog – king dog - bottle plant – butter plant - sock box - rug box - fence  Interference in Lab Studies Decay theory has difficulty explaining why performance in AB-CD lists is better than AB-AC lists Interference theory: – Performance on AB-AC lists is worse due to response competition – When the A cue is presented, both B and C compete to be retrieved in AB-AC lists – No competition is present in AB-CD lists What about decay from short-term memory? Re-analysis of all Brown-Peterson results by Underwood (1957) – Huge variation in how much material was forgotten over time – Big predictor of forgetting: Number of previous experimental trials More trials = poorer performance Underwood’s interpretation: Subjects suffer from proactive interference from previous trials What about decay from short-term memory? Almost no forgetting over 20 seconds in the first trial (Keppel & Underwood, 1962) – Memory quickly gets worse after that  So what’s happening in these experiments? – Previously learned stimuli cause interference at retrieval Learning more consonants makes it harder to retrieve what you just learned – So what if the stimulus type is switched? Interference theory predicts performance should improve Release from Proactive Interference: Wickens, Born, and Allen (1963) Switching the stimulus type causes big improvement in performance – Digits to letters, or letters to digits – New category hasn’t Change in stimulus been learned, so it type on the fourth should suffer less trial in the experimental interference condition Release from Proactive Interference: Wickens, Born, and Allen (1963) Many manipulations cause release from PI – Changing modality (auditory to visual), changing semantic category (e.g., fruits to occupations), changing part of speech, etc. No obvious decay explanation of these results! Even short-term memory is believed to be affected by interference Consolidation Theory  Consolidation Theory Learned memories are in one of two states: – Perseveration period: Memories are vulnerable – Consolidation phase: Memories that survive the perseverated phase are permanently stored and won’t be forgotten If consolidation does not occur, the memory will be forgotten  Three predictions 1. Protecting memories during perseveration should enhance consolidation and prevent forgetting – This is true: Mental inactivity following learning leads to better memory This is often tested by varying the length of time between two lists of items List 1 List 2 Time List 1 List 2 List 1 List 2 Time List 1 List 2 Better List 1 List 2 memory Greater for List 1 time due to between studying the two lists List 2 at a later time Time – Going to sleep after learning leads to better memory than being awake (Jenkins & Dallenbach, 1924) Mental activity while awake prevents consolidation  2. Interrupted perseveration should prevent consolidation and prevent memory from being stored – In other words: Interruption after consolidation occurs won’t impair memory, but interruption before consolidation should – This is confirmed by studies on retrograde amnesia  Retrograde Amnesia Loss of past memories after some trauma – Hippocampal amnesics such as H. M.: loss of ~3-5 years of most recent memories – Consolidation view: These memories were lost because they were not consolidated Lab studies: Induced retrograde amnesia shows similar effects – Electroconvulsive shock (ECS) – Removal of the hippocampus – Longer the delay between learning and ECS, the better the memory (Duncan, 1949) Control rats received no ECS When ECS given one hour after learning, rats perform as well as controls – Same applies to removal of the hippocampus Longer delay between learning and lesion, the better the memory  3. If consolidation is prevented, the memory is not stored and remembering should be impossible – If you re-test memories forgotten after ECS, they should not be remembered – ECS study (Quartermaine, McEwen, & Azmitia, 1972) - Varied delay of testing after ECS was administered When tested soon after ECS, no memory of learned responses When tested 72 hours after, rats exhibited memory This does not fit with the predictions of consolidation theory – Forgotten memories should stay forgotten  More on forgetting… Some memories never seem to get forgotten – Bahrick and colleagues: Foreign language courses: Virtually no forgetting from 3 to 50 years 80-90% recognition of HS classmates 50 years later  Which theory is right? There are a lot of hybrid theories – Consolidation + interference: Consolidation process protects older memories from interference Consolidation involves exporting memories from the hippocampus to the cerebral cortex  The shape of the forgetting function Mathematical form of forgetting contributes to the debate – Forgetting is non-linear with respect to time Linear forgetting would imply the same amount of information is lost with each unit in time Instead… – A lot of forgetting happens quickly – Less forgetting happens as time continues  The shape of the forgetting function – Specific functions: Exponential function: – Implies that loss is a fixed proportion for each unit of time – Example: if 50% of items are forgotten in the first hour, we will expect 50% of the remaining items to be forgotten on the next hour – Most decay functions in nature are exponential: radioactive decay, leak from a bucket, etc The shape of the forgetting function Power function: – Forgetting described by the amount of time raised to a power – Power functions imply that the proportional loss decreases with respect to time – In other words, if 50% of items are forgotten on the first hour, we might expect 40% of the remaining items to be lost on the next hour, 30% on the hour after that, etc  The shape of the forgetting function The data overwhelmingly support a power function (Rubin & Wenzel, 1996) Question: what causes forgetting to slow with time? – Wixted (2004) has argued that forgetting is driven by interference, but as time progresses, memories are more likely to be consolidated, which slows forgetting But do all of these findings require a consolidation explanation? Better memory when there is a rest between two lists argued to support consolidation theory Ecker, Tay, and Lewandowsky (2015): – There is similarly better memory for a given list when there is greater rest BEFORE a list – Not consistent with a consolidation explanation – consolidation can only occur after learning!  Better memory for longer post-study rest Data from Ecker et al. (2015)  Better memory for longer pre- study rest Data from Ecker et al. (2015)  So what explains these results? Ecker et al. (2015) argue these results support a modified interference theory based on temporal context – Interference between items depends on how close they were studied in time – More interference from items that were studied closer in time to each other – Pre-study and post-study rest produce greater separation between lists, and this leads to less interference between them List 1 List 2 When lists of items are separated List 1 List 2 in time, Greater time they are between less likely the two to lists interfere Time with each other Inhibition theory emerges  Inhibition Theory Inhibition theory emerged in the 1990’s, when most researchers subscribed to interference theory It began with the discovery of retrieval-induced forgetting (Anderson, Bjork, & Bjork, 1994) – Remembering can cause forgetting!  The RIF Paradigm Three phase design: – Study phase: learning pairs of categories and exemplars – Retrieval practice: test some of the studied exemplars from some of the categories – Test phase on all of the initial category-exemplar pairings Rp+ items: practiced items from practiced categories Rp- items: non-practiced items from practiced categories Nrp items: non-practiced items from non-practiced categories – These basically function as a control condition – We expect Rp+ items to do best – they were practiced! – RIF is evident if Rp- items perform worse than Nrp items  STUDY PHASE Category Exemplars cue fruit – orange fruit – apple fruit – banana fruit - pomegranate vehicle – motorcycle vehicle - train vehicle - truck vehicle - rickshaw  RETRIEVAL PRACTICE Some, but Not all not all, categories fruit – o___e are exemplars fruit – b_n__a practiced! from some categories “Vehicle” is are not practiced practiced here  TEST PHASE fruit – ___nge fruit – _pp__ fruit – ___ana fruit – p_______ate vehicle – m______le vehicle – t___n vehicle – tru__ vehicle - ______aw  TEST PHASE Rp+ items: fruit – ___nge these were fruit – _pp__ practiced fruit – ___ana earlier! fruit – p_______ate vehicle – m______le vehicle – t___n vehicle – tru__ vehicle - ______aw  TEST PHASE Rp- items: these come fruit – ___nge from a fruit – _pp__ practiced fruit – ___ana category (fruit) but the fruit – p_______ate items vehicle – m______le (“apple” and vehicle – t___n “pomegranat vehicle – tru__ e”) were not vehicle - ______aw practiced earlier  TEST PHASE fruit – ___nge Nrp items: fruit – _pp__ neither the fruit – ___ana exemplars or fruit – p_______ate the vehicle – m______le categories were vehicle – t___n practiced vehicle – tru__ vehicle - ______aw Benefits of retrieval practice – Rp+ items perform better than Nrp (control) items which were not practiced RIF effect: impairment of recall due to retrieval practice  Inhibition Theory Anderson, Bjork, and Bjork (1994) argued that RIF provides evidence that forgetting is due to inhibition – When attempting to remember an item, other items from the same category are inhibited or suppressed E.g., when cued with FRUIT and ORANGE is retrieved, other exemplars (BANANA and POMEGRANATE) are inhibited and it’s more difficult to retrieve them  Wait a minute… Can’t these results be explained by interference? – Practicing some category members strengthens the association between them – This makes it harder to recall other exemplars from the category – Maybe other category members aren’t actually weakened by retrieval?  ORANGE BANANA POMEGRANATE FRUIT GRAPES BLUEBERRIES APPLE Stronger association makes it such that ORANGE “ORANGE” will be recalled at the expense of other fruits when BANANA FRUIT is used as a cue POMEGRANATE FRUIT GRAPES BLUEBERRIES APPLE  Interference Dependence of Inhibition Theory Anderson et al. (1994) tested between the predictions of interference theory and inhibition theory – Unique prediction of inhibition theory: interference dependence of RIF Strong competitors during retrieval practice are suppressed and should exhibit large RIF effects Weak competitors do not need to be suppressed!  Orange comes to ORANGE mind because of the strong association, but it mismatches the BANANA ”B” cue… POMEGRANATE FRUIT B_____ GRAPES BLUEBERRIES APPLE  Orange is ORANGE suppressed – this makes it easier to recall BANANA BANANA POMEGRANATE FRUIT B_____ GRAPES BLUEBERRIE S is unlikely to come to mind, so it BLUEBERRIES doesn’t need to be suppressed APPLE  Interference Dependence of Inhibition Theory Anderson et al. (1994): categories had WEAK and STRONG associations to the cues – Key prediction of inhibition theory: STRONG Rp- exemplars should show the strongest RIF effects These should come to mind during retrieval practice, and require suppression – WEAK Rp- exemplars should show almost no RIF effects They do not intrude during retrieval practice – they don’t need to be suppressed! Zero on the y- axis RIF means present *no for differenc negative e between values: NRP and RP- RP- items items (no RIF) are worse than Only Strong RP- items suffer NRP from retrieval induced items  Cue Independence of Inhibition Theory In interference theory, forgetting is cue- dependent – More associations to a cue, the harder it is to remember something! Inhibition theory: cue-independence assumption of RIF – When an item is suppressed, it’s harder to remember regardless of the cue – Critical prediction: retrieval-induced forgetting should also be evident with novel cues  Cue Independence of Inhibition Theory Anderson and Spellman (1995): tested the cue independence assumption – Retrieval practice with categories and cues (e.g., FRUIT-APPLE) – Two test conditions: Standard test conditions with the categories before (FRUIT-APPLE) Novel cue condition: retrieve APPLE with RED as a cue – Confirmation of the cue independence assumption: Worse recall for RED-APPLE after retrieval practice!  Retrieval Dependence Assumption In inhibition theory, items are suppressed due to the competition that emerges at retrieval If there is no retrieval competition, there should be no RIF (retrieval dependence assumption) – Tested by Anderson, Bjork, and Bjork (2000) Restudying does not cause RIF Exemplars cuing their own category does not cause RIF – F____ - APPLE – Apple can cue FRUIT without competition from other categories in the experiment  Is inhibition theory correct? It’s still controversial! Raaijmakers and Jakab (2012) offered a critical review – Interference dependence assumption Has not generally replicated (Williams & Zacks, 2001) Did not generalize to other kinds of strengthening operations, such as repetition (Jakab & Raaijmakers, 2009) – Strong RP- items were repeated, weak RP- items non-repeated – RIF was observed for both strong and weak items, consistent with interference theory – Similar replication failures for cue independence and retrieval dependence  Current State of the Field What causes forgetting is still not completely resolved! – General consensus that interference takes place – Lack of consensus on the precise role that other factors take Various researchers believe that decay, inhibition, or consolidation operate in conjunction with interference Decay still places a role in theories of short-term memory  Current State of the Field Why hasn’t this been resolved? – Difficult question to answer! – Limited data: experiments only provide a short snapshot into the mechanisms of memory ~45 minutes of data from a limited sample of participants – Limited brain recording techniques Mechanisms of memory formation cannot be directly observed in humans without invasive surgery Current State of the Field – Computational modeling of memory is still in its infancy One could conceivably build a model with various mechanisms (interference, decay, inhibition, and consolidation) and measure their respective influences Computational models can also address these influences across a range of different memory tasks, rather than just a single task  Learning Outcomes Understand the laws of memory Understand the decay theory of forgetting and the evidence to support it Understand the mechanisms of interference theory – Understand the conditions under which interference theory predicts that memory should be better or worse, and how these differ from decay theory Understand the mechanisms of consolidation theory and the data that were used to support its predictions Understand the different forgetting functions and their implications for psychological theories of forgetting  Learning Outcomes Understand inhibition theory and the details of the paradigm used to test it (RIF) – Understand how RIF is measured in the paradigm – Understand the various RIF predictions that were used to support inhibition theory over interference theory  Next week: False memory and its implications!