Transcript May12

Cognitive Processes
PSY 334
Chapter 7 – Human Memory:
Retention and Retrieval
What is Forgetting?
 Do memories still exist in mind when we
cannot remember?
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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:
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Savings found with both recall and
recognition tests.
The Retention Function
 Wickelgren – studied the retention
function:
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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.
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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.
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Substantial practice effect.
Slow decline after 3 yrs.
Drop-off at end due to physical aging.
 Barnes – decrease in long-term
potentiation with delay.
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Mirrors retention function.
Decay theory of forgetting – LTP changes.
Interference
 Interference paradigm – two groups
defined:
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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:
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The more associations, the less activation
can spread to any particular structure.
 Anderson – fan effect:
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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:
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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.
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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:
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Irrelevant facts interfere.
Relevant facts aid memory compared to
single fact learning.