Chapter 11

1. Chapter 11 Forgetting

2. Memory • Internal record or representation of past experience • Not necessarily the same as the original experience

3. Comparative Psychology View of Memory • Not experiences stored or retrieved • Experience’s ability to change an organism’s behaviour under certain conditions • Stimulus control

4. Forgetting • Deterioration in learned behaviour following a period without practice • Defined behaviourally • Note: extinction is not the same as forgetting

5. Measuring Forgetting • Training • Waiting for some period (“retention interval”) • Testing

6. Free Recall Method • Train, wait, test • Performance deterioration? • “All-or-nothing” test of behaviour • May not be appropriate for complex tasks • Some elements remembered, others not

7. Prompted (Cued) Recall • Give prompts to increase likelihood of behaviour • Number of prompts needed?

8. Relearning Method • Reinstall original training procedure after retention period • How many trials (or time) needed compared to original training to return to initial level of proficiency?

9. Recognition Method • Subject only has to identify material previously learned • E.g., distinguish between original stimulus and a number of distracter stimuli

10. Delayed Matching to Sample • Show S+ • Wait • Choose from S+ and S- Sample Delay Matching

11. Extinction Method • Train two subject groups • Put both on extinction, but one has delay between training and extinction and the other doesn’t • Compare rate of extinction

12. Gradient Degradation Method • Establish stimulus control • Measure generalization gradient over time • If generalization gradients flatten: forgetting

13. Variables in Forgetting

14. Retention Interval • Time between learning and testing • Greater the interval, less retained (i.e., more forgetting) • But, time is not an event (time doesn’t account for forgetting) • Need causal factors

15. Degree of Learning • Overlearning • Learn to asymptote, then keep training • Point of diminishing return

16. Prior Learning • Meaningful material easier to retain than random material (e.g., learning katas) • Prior experience important in determining what is meaningful (e.g., words in known or unknown language)

17. DeGroot (1966) • Arranged chess pieces in legal patterns on board • Chess masters and novices; 5 seconds to observe • Masters reproduced arrangement 90% of time, novices only 40% • Is this prior experience, or do chess masters forget less than other people?

18. Chase & Simon (1973) • Chess pieces placed randomly on board • Masters no better than novices at recall • Past learning of “legal” arrangements is what increased masters’ performance in deGroot (1966) study

19. Proactive Interference • Previous learning interferes with recall • Paired Associate Learning (PAL) technique • Subjects learn paired lists, tested with 1 item and must recall second • All learn A-C list, but some previously learned A-B list • In testing, give A and ask to recall C • Those with A-B learning have more difficulty recalling C when given A

20. Proactive PAL Design Experimental Group Control Group

21. Levine & Murphy (1943) • Proactive interference with attitudes • Students read pro- and anti-communism passages • Students who had prior pro-communist attitudes forgot anti-communist elements of passages but remembered pro-elements (and vice versa) • Attitudes not innate; effect of prior learning

22. Subsequent Learning • Inactivity during retention interval leads to less forgetting than activity • Implies forgetting partly based on learning new material 100 50 sleep Recall (%) awake 0 2 4 6 8 Hours after learning tested

23. Retroactive Interference • New learning interferes with ability to recall earlier learning • PAL technique • Subjects learn A-C, but some then learn A-B • Test by giving A and recalling C • Subjects who learned A-B have worse recall for C

24. Retroactive PAL Design Experimental Group Control Group

25. Context • Learning occurs in a context • Various stimuli around the learner • These stimuli serve as cues to evoke a behaviour • If stimuli absent, may have cue-dependent forgetting • Stimulus control

26. Perkins & Weyant (1958) • Train two groups of rats in two mazes, one black, one white • 1 minute retention interval • Half of each group tested in original maze, half in maze of opposite colour • Opposite colour rats did poorly compared to original maze tested rats

27. 100 50 Avoidance (%) 0 12 24 36 48 60 72 84 Retention Interval (hr) Kamin (1957) • Gave rats avoidance learning, tested at various retention intervals.

28. State-Dependent Learning • Train under a particular physiological state (e.g., drug condition) and test under various states • Recall best when in the same state as training

29. Application: Foraging • Finding food • Cache: food store • Retrieval of food later • Spatial memory • Wide variety of species • Accuracy can be quite high for very long times

30. Application: Eyewitness Testimony • Notoriously poor • Basic issue of retention interval and forgetting • Also the nature of the question used to retrieve information

31. Loftus & Zanni (1975) • Subjects watched film of auto accident • Asked “Did you see <the>/<a> broken headlight?” • “the” subjects twice as likely as “a” subjects to say “yes” • Actually, no broken headlight shown • Reinforcement history • Previous conditioning: “the” (definite article) implies presence; “a” implies possible presence

32. Learning to Remember • In essence, improving learning • Practice increases retention • Overlearning • Mnemonics • Context cues • Prompts