Cognitive ProcessesPSY 334

Chapter 6 – Cont.Chapter 7 – Human Memory: Retention and RetrievalAugust 5, 2003

Incidental Learning

It does not matter whether people intend to learn something or not. What matters is how material is processed.

Orienting tasks: Count whether word has e or g. Rate the pleasantness of words. Half of subjects told they would be asked

to remember words later, half not told. No advantage to knowing ahead of time.

Flashbulb Memories

Self-reference effect -- people have better memory for events that are important to them and close friends.

Flashbulb memories – recall of traumatic events long after the fact. Seem vivid but can be very inaccurate.

Thatcher’s resignation: 60% memory for UK subjects, 20% non-UK

Neural Correlates of Encoding

Better memory occurs for items with stronger brain processing at the time of study: Words evoking higher ERP signals are

better remembered later. Greater frontal activation with deeper

processing of verbal information. Greater activation of hippocampus with

better long-term memory.

Two Ways of Testing Memory

Recall Essay exams

Recognition Multiple-choice exams

Snow White’s dwarfs demo

What is Forgetting?

Do memories still exist in mind when we cannot remember? Penfield – stimulated areas of the brain

and got reports of recall from childhood. No way to check the accuracy of reports.

Nelson – some savings are evident even when subjects cannot remember items: Savings found with both recall and

recognition tests.

The Retention Function

Wickelgren – studied the retention function: Performance is a function of delay. Log (d’) = A – b log T Where: T is delay, d’ is performance

(memory strength). Power law of forgetting -- power function

becomes linear when plotted on log-log scales.

Rate of Forgetting

Retention function shows diminishing loss (forgetting) with delay.

Theory of short-term memory predicts sharp drop-off followed by stable memory. Since all retention functions are like this,

there is nothing special about short-term memory compared to long-term memory.

Practice postpones the point of decay.

Long-Term Retention

Bahrick – studied retention of English-Spanish vocabulary over 50 years. Substantial practice effect. Slow decline after 3 yrs. Drop-off at end due to physical aging.

Barnes – decrease in long-term potentiation with delay. Mirrors retention function. Decay theory of forgetting – LTP changes.

Interference

Interference paradigm – two groups defined: Experimental group – learns new

associations for previously learned list Control group – learns entirely new list

Typically the experimental group does worse after a delay.

Does this mean that it is difficult to maintain multiple associations?

Fan Effect

There is a limit to how much activation can spread within a network: The more associations, the less activation

can spread to any particular structure. Anderson – fan effect:

Recognition time increases with the number of facts about a person and a location.

Preexperimental Memories

Does knowledge brought into an experiment interfere with new learning?

Lewis & Anderson – facts about Napoleon: Fantasy facts – learned during experiment True facts – from the real world False facts – not studied in experiment and

not true in the real world Fan effect occurs with all three fact types

Interference vs Decay

Less forgetting during sleep than when awake. Occurs because material is retained better

when learned at night. Night is period of highest arousal.

Forgetting functions may reflect interference from unknown sources.

Decay theories do not specify any mechanism for decay.

Effects of Redundancy

Interference occurs only when learning multiple memories that have no relationship to each other.

Bradshaw & Anderson – compared relevant and irrelevant fact learning: Irrelevant facts interfere. Relevant facts aid memory compared to

single fact learning.

Retrieval and Inference

Much of memory is inference at the time of recall – not actual recall of facts.

Bransford et al. -- inference can lead to incorrect recall: Turtles resting on or beneath log. Subjects were most confused by

sentences whose meaning was implied by the studied sentences.

Inference-Based Intrusions

Sulin & Dooling – subjects add details not present during learning: Carol Harris vs Helen Keller “She was deaf, dumb and blind.” 5% Carol Harris but 50% Helen Keller

subjects falsely recognized the sentence. Inferences are made at test-time.

More inferential errors occur with delay.

Plausible Retrieval

Reder – much of recall is plausible inference not actual recall. Darth Vader inferred to be evil, not

remembered to be evil. Heir to hamburger chain story – subjects

asked to recall exact details and make plausible inferences.

After a delay, plausible inference is faster and does not decay as much as exact memory, with no fan effect.

Inference and Elaboration

Elaboration leads to more inferences. Information added as a “theme” to a story

results in better recall of studied material and more inferences.

Intruded inferences are not necessarily “errors” but help guide our thinking and behavior.

Listerine court case – false inferences, not just false statements, not permitted.

Memory Errors

When exact memory is needed, inferences and reconstructive processes can be misleading.

Loftus -- additional details and suggestion can change what is recalled.

John Dean’s recall vs what Nixon recorded – gist was right but not details.

False memory syndrome – memories that never happened can be “planted.”