Cognitive Processes PSY 334 Chapter 7 – Human Memory: Retention and Retrieval

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.