Week 9 Basics of Memory - Learning & Forgetting

Question 1

Many findings from Ebbinghaus’s experiments

Answer 1

• Spacing effects: repetitions more effective if you space them out over time rather than mass them consecutively
• List length effects: Worse memory when you study longer lists versus shorter lists
• Forgetting curve: the shape of how memory declines over time

Question 2

Ebbinghaus contribution on experimental tradition of memory

Answer 2

–Presenting randomized lists of “non-meaningful” stimuli to participants under controlled conditions
–Control for exposure duration, retention interval, etc.
-Various reasons why something is not remembered

Question 3

Decay Theory

Answer 3

Stored memories fade over time
–Brown-Peterson paradigm: Subjects learn trigram, count backwards by seven for a period of time (to prevent rehersion)
• Almost no memory after ~20 seconds

Question 4

Interference Theory

Answer 4

• Started with John McGeoch (1932) – claimed that decay theory is conceptually flawed
–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

Question 5

Interference Theory, why is there competition

Answer 5

–When we learn, we associate things together
–When presented with one of those things in isolation (the cue), we can recall the associate
=The more associations there are, the harder it is to remember thing

Question 6

Interference theory and lockdown

Answer 6

• 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

Question 7

What is interference

Answer 7

More associations to a cue, the harder it is to retrieve the correct memory
– proactive interference Inability to retrieve new associates can be because of interference from older ones
-retroactive interference Inability to retrieve old associates can be because of interference from newer ones

Question 8

Interference in Lab Studies

Answer 8

• 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
• 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)

Question 9

result of Interference in Lab Studies

Answer 9

Decay theory has difficulty explaining why performance in AB-CD lists is better than AB-AC lists
–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

Question 10

What about decay from short-term
memory

Answer 10

• 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

Question 11

Release from Proactive Interference:
Wickens, Born, and Allen (1963)

Answer 11

• Switching the stimulus type causes big improvement in performance
–Digits to letters, or letters to digits
–New category hasn’t been learned, so it should suffer less interference
• Many manipulations cause release from PI
• No obvious decay explanation of these results

Question 12

Consolidation Theory

Answer 12

• 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

Question 13

Three predictions of consolidation theory

Answer 13

1. Protecting memories during perseveration should enhance consolidation and prevent forgetting
2. Interrupted perseveration should prevent consolidation and prevent memory from being stored
3. If consolidation is prevented, the memory is not stored and
   remembering should be impossible

Question 14

Proof for Protecting memories during perseveration should enhance consolidation and prevent forgetting

Answer 14

mental inactivity following learning leads to better memory (as it provides time for memories to be consolidated).
• Going to sleep after learning leads to better memory than being awake (Jenkins & Dallenbach, 1924). Mental activity whilst still awake prevents memory consolidation.

Question 15

Proof of Interrupted perseveration should prevent consolidation and prevent memory from being stored

Answer 15

• This is confirmed by studies on retrograde amnesia – where most recent memories before the trauma were lost because they were not consolidated.
• Studies involving induced retrograde amnesia show similar effects – e.g. removal of the hippocampus, electroconvulsive shock.
• The longer the delay between learning and electroconvulsive shock (ECS), the better the memory (Duncan, 1949). When ECS was given one hour after learning, rats performed as well as the controls (same applies to removal of the hippocampus). This is because these memories are consolidated in that time, and no longer require the hippocampus. The longer the delay between learning and lesion, the better the memory.

Question 16

Study of If consolidation is prevented, the memory is not stored and remembering should be impossible

Answer 16

If you re-test memories forgotten after ECS, they should not be remembered.
Quartermaine, McEwen & Azmitia, 1972: when tested soon after ECS, rats showed no memory of learned responses. However, when tested 72 hours after, the rats exhibited memory. This does NOT fit with the predictions of consolidation theory (is an example of spontaneous recovery)

Question 17

Some memories never seem to be forgotten

Answer 17

–Bahrick and colleagues:
• Foreign language courses: Virtually no forgetting from 3 to 50 years
• 80-90% recognition of HS classmates 50 years later

Question 18

Hybrid theories:

Answer 18

Consolidation + interference: the consolidation process protects older memories from interference
• Consolidation involves exporting memories from the hippocampus to the cerebral cortex

Question 19

The shape of the forgetting function

Answer 19

• Mathematical form of forgetting contributes to the debate
–Forgetting is non-linear with respect to time A lot of forgetting happens quickly but Less forgetting happens as time continues

Question 20

Exponential function of forgetting fuction

Answer 20

– 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

Question 21

Power functions shape of forgetting

Answer 21

– 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

Question 22

The shape of the forgetting function conclusion

Answer 22

• The data overwhelmingly support a power function (Rubin & Wenzel, 1996)
–Wixted (2004) has argued that forgetting is driven by interference, but as time progresses, memories are more likely to be consolidated, which slows forgetting

Question 23

Temporal context

Answer 23

® Ecker, Tay & Lewandowsky (2015) found that there is similarly better memory for a given list when there is greater rest BEFORE a list. This supports a modified interference theory based on temporal context.
® Temporal context suggests that interference between items depends on how closely the items were studied in time. There is more interference from items that are studied closer in time to each other.
® Pre-study and post-study rest produces greater separation between lists, and this leads to less interference between them

Question 24

Inhibition Theory

Answer 24

• 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!

Question 25

The RIF Paradigm

Answer 25

• 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

Question 26

Anderson, Bjork, and Bjork (1994) and inhibition theory

Answer 26

• 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

Question 27

Interference Dependence of Inhibition
Theory

Answer 27

• 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!

Question 28

Inhibition theory: cue-independence assumption
of RIF

Answer 28

–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

Question 29

Anderson and Spellman (1995): tested the cue
independence assumption

Answer 29

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!

Question 30

Retrieval Dependence Assumption

Answer 30

• 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

Question 31

Is inhibition theory correct

Answer 31

• 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

Question 32

Current State of the Field

Answer 32

• 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

Question 33

Why hasn’t the reason for decay havent been resolved?

Answer 33

–Difficult question to answer!
–Limited data: experiments only provide a short snapshot into the mechanisms of memory
–Limited brain recording techniques
• Mechanisms of memory formation cannot be directly observed in humans without invasive surgery
–Computational modeling of memory is still in its infancy