Outline Forgetting

Home , Interference theory, Tip of the tongue

Psychology 263: Introduction to Cognitive Processes

Forgetting, sleep and memory

Outline

• Forgetting • Ebbinghaus & the forgetting curve • The forgetting curve in the real world • Why do we forget? – Consolidation theory – Interference theory (decay vs. interference) – Functional decay theory – Retrieval failure

Forgetting

• Memory is not perfect, we need to give ourselves room to forget • Is a “perfect” memory really desirable? • Forgetting is necessary but seems troublesome because we only notice we’ve forgotten something when we need it again • Why do we forget names/faces, punchlines to jokes, etc. Hermann Ebbinghaus (1850 - 1909) • Bottom up, episodic approach to studying memory and forgetting

• Learned lists of 13 nonsense syllables

• Re-tested himself in intervals ranging from 20 minutes to a month later

• Recorded amount of time to relearn the list (savings method)

% Mean Savings

The forgetting curve in the real world • Problem with Ebbinghaus…learned nonsense material • Does Ebbinghaus’ forgetting function generalize to more real world material? – Names/faces – Foreign languages – Motor skills – Bahrick and colleagues – Linton: autobiographical memory

• Do we really know anything about forgetting? • On these graphs, don’t pay attention to specific numbers, just compare the overall pattern to Ebbinghaus’ function Bahrick et al.: Memory for names and faces of high school classmates

Names/faces

• Multiple memory tests (name/picture recognition, name matching, picture matching/cueing, free recall) • Strong memory up to 25 years after graduation • Only slight forgetting with recognition measures • Large forgetting after 50 years (not sure if this is due to age or time)

Bahrick: College Professors memory for names/faces of students Names/faces

• College teachers memory for names/faces of former students • Forgetting is more linear in nature than logarithmic • Memory is quite good on recognition measures

Bahrick: Memory for a foreign language (that is rarely used)

Memory for foreign languages

• Looks a bit like Ebbinghaus’ curve (initially) but much less pronounced • Level to which language was initially learned is an important determinant of what is forgotten • Pretty good memory years later even if it had been used infrequently • Don’t believe this? Learn French, years later, try to learn Spanish How about memory for motor skills: CPR

Complex skills

• CPR – forgotten at a rate strikingly similar to the Ebbinghaus curve even though it’s an extremely important skill (why? Never used? Rarely practiced? Not of interest to most people)

Complex skills

• CPR is an important skill that is easily forgotten, what about less important skills? • Flying an airplane is a skill that is forgotten very slowly even if never practiced after originally learned • If a warm-up trial is given prior to test, virtually no forgetting occurs • Not true of all motor skills (some diminish quickly if not practiced) • Is it true that you never forget how to ride a bicycle? Linton: Memory for autobiographical events

Memory for meaningful episodic material • Marigold Linton…diary method. • Write down the events of your day at day’s end • Rate of forgetting: only about 6% a year • Does this mean she has a better memory than most? • Meaningfulness of information and selection of incidents probably helped memory relative to Ebbinghaus’ over- exposure to nonsense syllables • More similar to how we probably remember real world events (occasionally recalling them and telling stories to people)

What does this tell us?

• We know very little about forgetting • Ebbinghaus’ studies are not as useful as they once appeared and that forgetting curve is misleading if taken too literally • Has this stopped psychologists from theorizing (re: blindly guessing) about the causes of forgetting? Why do we forget?

• Three main explanations – Storage problems – Decay of information/interference of other information (why?) – Retrieval failures (our springboard to talking about retrieval)

Consolidation theory • Not quite a theory of forgetting, based on the idea that forgotten information wasn’t stored well initially (how can you forget something that wasn’t in memory to begin with?) • Learning is not complete at the time that practice or rehearsal ends • Perseveration (Muller & Pilzecker, 1900) – the consolidation of information to memory

Consolidation theory • If perseveration is interrupted in any way the trace will not be consolidated and recall will not be possible • The longer the perseveratory period, the stronger or more consolidated the memory trace • Initial view: perseveration is STM, consolidated trace is LTM Consolidation theory • Many different versions of consolidation theory, all rest on the same three predictions • Three key predictions made by consolidation theory: – Mental inactivity is more conducive to perseveration – Consolidation does not occur if the perseveration period is interrupted – Without consolidation, an item should never be recalled • More perseveration should lead to better recall

Support for consolidation

• Ebbinghaus: The first to note that he remembered more nonsense syllables when he slept between study and test…led to numerous related studies

• Jenkins & Dallenbach (1924) • Yaroush, Sullivan, & Ekstrand (1971) • Minami & Dallenbach (1946) • Retrograde amnesia

Jenkins & Dallenbach (1924)

• if perseveration is critical to LTM, then going to sleep immediately after learning should help memory • learn a short list of Ebbinghaus-type nonsense syllables (e.g., TUV, BIJ, etc) • sleep or stay awake for 1 - 8 hours prior to test

• Yaroush, Sullivan, & Ekstrand (1971) • Minami & Dallenbach (1946) Sleep 0.9 0.8 0.7 asleep 0.6 0.5 0.4 0.3 0.2 awake

Proportion Correct 0.1 0 12345678 Hours Between Study & Test One interpretation: Sleep facilitates perseveration

Yaroush, Sullivan, & Ekstrand (1971)

• Memory is even better if we prevent subjects from dreaming while they sleep

• Note: while sleeping between study helps learning, learning while you sleep DOESN’T WORK

Minami & Dallenbach

• Cockroaches as subjects • A response is conditioned in cockroaches (avoiding a dark compartment of a box) • Cockroaches then free to move around or lie inert (tissue paper lined cone) • Conditioned response lasts longer in inert cockroaches Another piece of evidence for consolidation theory: Retrograde Amnesia

• A loss of memory for events that occur before some sort of trauma/injury • Even though memory is usually recovered/restored over time, memory for the events that happen immediately before the injury are never remembered • Trauma interrupts perseveration?

The problems

• Despite some support for the first notion (inactivity better than activity), the other two ideas are difficult to test experimentally • What really goes on during perseveration? It’s difficult to know if a perseveration period has been interrupted or if it’s occurring because we don’t know what defines “mental inactivity” • If we make someone wait in a room for 10 minutes before recalling something, what are they doing?

The problems

• Most of this earlier research occurred with animal subjects…humans have more complex thought structures • In the early days of consolidation work, “retrieval” was not an accepted concept so it was easy to say that something that was forgotten wasn’t consolidated (circular) • We didn’t know then what we know now (i.e., implicit memory, it’s forgotten but not gone) • Too rigid an idea Consolidation theory

• Despite problems, may be partially correct • We don’t know enough about physiological processes and their cognitive consequences to determine this – E.g., memory isn’t as good if sleep occurs in the afternoon – Circadian rhythms (aging differences reduced when older adults run at “peak” times)?

Interference theory

• Rather than arguing that information doesn’t enter memory (consolidation), this is the notion that other information interferes • Previous popular idea: information decays over time • McGeoch (1932) – It can’t just be decay! – Iron rusts over time, but time is not the causal agent (oxidation is, this unfolds over time) – Memories forgotten over time, what is the causal agent? • Retroactive vs. proactive interference

Interference theory

• Retroactive interference: information you learn after the original learning episode interferes with the previously learned material • Proactive interference: information you’ve learned prior to a learning episode disrupts your ability to remember that information Interference

Retroactive

Exp’tal Learn A Learn B Recall A Control Learn A --- Recall A

Proactive

Exp’tal Learn B Learn A Recall A Control --- Learn A Recall A

Evidence for interference theory

• Everything we just went over for consolidation theory: rather than consolidating, mental inactivity means less of a likelihood of retroactive interference

Proactive interference

• Retroactive interference is intuitive, forgetting out of need…what about proactive interference? • Discovered by Underwood in a literature review (the more lists a subject learns prior to a final list, the worse their memory is for that final list) • Underwood noted that when he redid the Ebbinghaus study, he forgot far less (20%) than Ebbinghaus (60%) over time

• Real world examples of PI: wrong name, mom Proactive Interference Underwood (1948, 1957, 1964) 1 0.9 0.8 . 0.7 . 0.6 0.5 0.4 .. 0.3 . . 0.2 . .

Proportion Correct Proportion 0.1 0 1 3 5 10 25 50 # of Prior Lists

McGeoch’s 3 mechanisms of interference

• McGeoch thinks that inability to recall something is due to subjects recalling unwanted memories (interference)…information is never actually lost • Three mechanisms that can cause forgetting – Response competition: two or more potential responses to a memory query (e.g. List A: cat-dog List B: cat-mouse) – Altered context: context dependent memory – memory worse when tested in a different context (no retrieval cues) – Set: A special version of context effects (where do I know that person from)

Famous example of a “set” effect

• Part-list cuing • Originally explained in terms of inhibition • Actual cause: strategy disruption…your mental set has been violated Problems for interference theory

• Difficult to account for PI and no posited mechanism to account for it (why hold onto the name of an old partner or your old telephone number)…RI is intuitive, forgetting out of need • McGeoch was influential enough though that the notion of decay is gone now

Decay vs. Interference

• One nice thing about PI…killed decay outright • Brown-Peterson paradigm • Why: names at a party, irregular parking spot (old habits wreck new learning) • A new idea: functional decay theory (Altman & Gray, 2002)…information decaying out of necessity when new information overwrites it

Retrieval failure

• One of the most accepted theories nowadays though the idea of retrieval in general was not widely utilized until the 1960’s. • Big advantage – doesn’t rely on only a single mechanism of forgetting (e.g. decay vs. interference, can be multiple things) • Retrieval failure example: trying to remember something today that you can’t, comes back to you tomorrow • Another example: rushing to the internet, remembering on the way • Forgetting here is temporary, happens all the time (if you knew where to look, you’d remember) Quick intro to retrieval (more to come)

• Capital of Rhode Island? • How long would it take us to figure something out if we had to search through every item we have in memory • Tomkins (1970): 400 years; Norman (1968): N/2; Landauer (1986): 109 • If you know 10 billion things and you can search an item every tenth of a second, how long would it take you to find something (about 16000 years) • LTM is “content addressable” – we know where to look • …and now back to forgetting

Recall vs. Recognition

• Arguably the most convincing evidence for retrieval failure? (Tulving) • We can be influenced by information we can’t consciously recall • Retrieval was not a viable construct until Tulving made the explicit/implicit distinction

Explicit/implicit

• Can explicitly remember about 40% of material in a list learning study but estimates for implicit memory are upwards of 90% • Lots of information is available to us that we are not conscious of • Otherwise, no difference between recall and recognition More Tulving Goodness

• With successive retrievals of a list of words, subjects often recall the same number of words, but not the same words (available but not accessible, much like recognition tasks…but is this merely evidence of a drawback of experimental research???) • Do people in experiments really recall everything they can?

Other evidence in support of retrieval failure • The effect of retrieval cues – Imagine you hear something in lecture and you think about it in the context of something you heard in another lecture (multiple retrieval paths to the same memory makes recall more likely) – E.g. Does the current situation in Iraq remind you of anything you learned in class recently…memory connection to me here is useless • State dependency • Encoding specificity • Tip of the tongue phenomenon

Other evidence in support of retrieval failure • State dependency – memory is improved when retrieval occurs in the same state as encoding (e.g., internal context) • Encoding specificity – similar to state dependency…match between contexts at test and retrieval are key (when writing the final exam, imagine original context…e.g., external context) • Tip of the tongue phenomenon Other evidence in support of retrieval failure • Tip of the tongue phenomenon • William James - "It is a gap that is intensely active. A sort of wraith of the name is in it, beckoning us in a given direction, making us at moments tingle with the sense of our closeness and then letting us sink back without the longed-for term."

Retrieval failure

• The most accepted of the aforementioned theories • Like most competing theories, it’s probably the case that the real explanation for forgetting is a combination of the theories I’ve just outlined • Create your own “unified” theory of forgetting, get rich and famous