Transcript Aug5

Cognitive Processes
PSY 334
Chapter 6 – Cont.
Chapter 7 – Human Memory:
Retention and Retrieval
August 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% nonUK
Neural Correlates of Encoding
 Better memory occurs for items with
stronger brain processing at the time of
study:
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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:

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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.


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.


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:

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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.”