Chapter 11 Forgetting

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

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

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

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

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

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

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?

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

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

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

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

Variables in Forgetting

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

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

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)

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?

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

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

Proactive PAL Design Experimental Group Phase 1 (A-B)Phase 2 (A-C)Phase 3 (C?) apple-ballapple-combapple-??? aardvark-birchaardvark-caraardvark-??? atom-bananaatom-codatom-??? ant-bombant-creamant-??? Phase 1 (N/A)Phase 2 (A-C)Phase 3 (C?) apple-combapple-??? aardvark-caraardvark-??? atom-codatom-??? ant-creamant-??? Control Group

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

Subsequent Learning Inactivity during retention interval leads to less forgetting than activity Implies forgetting partly based on learning new material Recall (%) Hours after learning tested sleep awake

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

Retroactive PAL Design Experimental Group Phase 1 (A-C)Phase 2 (A-B)Phase 3 (C?) apple-combapple-ballapple-??? aardvark-caraardvark-birchaardvark-??? atom-codatom-bananaatom-??? ant-creamant-bombant-??? Phase 1 (A-C)Phase 2 (N/A)Phase 3 (C?) apple-combapple-??? aardvark-caraardvark-??? atom-codatom-??? ant-creamant-??? Control Group

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

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

Kamin (1957) Gave rats avoidance learning, tested at various retention intervals. Avoidance (%) Retention Interval (hr)

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

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

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

Loftus & Zanni (1975) Subjects watched film of auto accident Asked “Did you see / 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

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