1. Cognitive ProcessesPSY 334 Chapter 7 – Human Memory: Retention and Retrieval

2. 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.

3. 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.

4. 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.

5. 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.

6. 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?

7. 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.

8. 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

9. 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.

10. 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.