Transcript Chap4

BHS 499-07
Memory and Amnesia
Models of Memory
Plato’s Model
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Plato extended the wax tablet metaphor
to refer to birds in an aviary.
• Birds are located in specific places.
• Search processes are needed to hunt for
them.
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William James referred to primary and
secondary memory.
• New experiences linger briefly and need not
be stored forever (secondary memory).
The Modal (Multi-Store) Model of
Memory
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Modal refers to sensory modality (way of
receiving info from outside world).
Heuristic means “rule of thumb” – this
theory of stages is a way of thinking
about memory not to be taken literally.
This multistore (modal) model was the
guiding framework for decades.
Multiple Memory Systems
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Memory is not unitary but consists of
several subcomponents (parts).
Atkinson & Shifrin:
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Tulving’s Triarchic Theory:
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• Sensory store, short term, long term stores
• Episodic
• Semantic
• Procedural
Autonoetic (self)
Noetic (formal knowledge)
Anoetic (automatic skills)
Other Classifications
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Declarative vs Nondeclarative
• Declarative includes episodic and semantic
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memory
Nondeclarative includes procedural memory,
classical conditioning and priming
Explicit vs implicit
• Explicit memory involves consciousness,
implicit does not.
Beyond Multi-store Models
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Levels of processing theory (Craik &
Tulving) – it isn’t where memories are
processed that matters, but how.
• Shallow vs deep processing
• Elaborative rehearsal vs repetitive rehearsal
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Short term memory was replaced by
Baddeley’s model of the central
executive (where rehearsal takes place).
Current Issues
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Neurological bases for memory
Impact and importance of emotion on
memory
Use of multiple memory sources (fuzzy
trace theories)
Embodied cognition – how our grounding
in the world influences memory
Sensory Memory
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Three sensory registers discussed by
Radvansky and Parkin texts:
• Visual sensory register (iconic memory)
• Auditory sensory register (echoic memory)
• Touch sensory register (haptic memory)
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Briefest duration -- < 5 sec
Retains characteristics of the stimulus so
that meaning can be interpreted
Iconic Memory
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How many items, how long does it last?
It is difficult to study the capacity of
iconic memory because items fade
before people can report them aloud.
• Averbach found that increased presentation
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time did not improve memory for dots.
Sperling’s partial report procedure showed
that an entire array was remembered well, but
only for ~.250 seconds, ¼ sec.
Increasing the duration of
the stimulus increases the
dots remembered up to 6,
but not much after that.
Sperling’s partial report procedure showed greater recall
when a tone cued people to look at a specific line immediately
after viewing the stimulus, but not after a delay.
Anorthoscopic Perception
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Images in the iconic register are
combined to form a single mental
representation.
Anorthoscopic perception (seeing more
than is there) – an image is passed
through a slit at 250-300 ms (quickly).
• The original icon is compressed to build up
the entire representation – so not an after
image but a constructive process.
The longer a stimulus
is viewed, the closer
the response is to the
actual stimulus (see
Actual and 2110 ms)
Trans-Saccadic Memory
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Saccade – an eye movement (~ 30 ms).
• Our eyes are constantly moving over the
objects in the world.
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Fixation – when eyes stop on a point
(typically ~ 300 ms).
A trans-saccadic memory is needed to
build-up a mental representation from all
of the eye movements
Subjects were
unable to make the
necessary
comparisons in
either of these two
tasks, so there
must exist a transsaccadic memory
store.
Change Blindness
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Visual memory is not always accurate.
• Movies frequently contain errors of detail that
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go unnoticed – continuity errors
Only 33% of subjects noticed the change of
an actor of the same ethnicity & gender.
Top-down expectations affect what is
noticed.
• Students notice students not construction
workers, or changes that belong in a scene.
Echoic Memory
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Echoic memory lasts briefly to permit a
mental representation to be formed.
• More exists in memory than can be reported.
• Retention of info is longer (~ 4 sec).
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Because sounds can only be heard
once, info is kept available longer.
Flow of speech is constructed from a
series of passing sounds.
Haptic Memory
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Less studied.
Air jets were used in a whole/partial
report procedure.
• Duration was ~ 1.3 seconds.
Short Term Memory
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Dispute – is short term memory
qualitatively different from long-term
memory?
• Or is it just the part of long term memory that
is currently active?
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Severely limited in capacity (unlike
sensory registers).
• Miller’s magic number of 7 +/- 2 (or 4 +/- 1).
Chunking
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We are capable of thinking about more
by forming units out of smaller pieces of
information.
• The number of chunks is the same as the
number of units that can be remembered.
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Prior knowledge guides the chunking
process.
• Race lengths, chess games are large chunks
S.F.’s digit span improved with practice as he learned to
chunk digits in terms of race results.
Duration of STM
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Without active attention, info is forgotten
in ~ 30 sec (some sources say 15)
• How do you tell people not to think about
something so you can test it?
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Is forgetting due to decay or
interference?
• Decay -- passage of time erases trace.
• Interference – new info displaces the old
This task tests for
interference.
This task tests for delay.
STM Retrieval
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Does retrieval involve a serial or a
parallel search?
• Sternberg’s paradigm of digits followed by a
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probe showed serial exhaustive search.
Most people find this result surprising,
showing why self-report may be flawed.
An alternative explanation is parallel search
with limited resources (requiring more time).
Most likely both processes are involved.
Serial Position Curves
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Position in a list of items affects likelihood of
being recalled.
Primacy effect – items at the beginning of a list
are remembered better.
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Due to encoding in long term memory via more
rehearsal.
Recency effect – items at the end of the list are
remembered well because still active in short
term memory.
Modifying Serial Position Effects
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Placing an irrelevant item at the end of a
list eliminates the recency effect.
Memory for actions is different – no
primacy effect because the focus is on
individual actions so less rehearsal.
Suffix effect – recency effect is
diminished when new info is added at
the end (the more the greater the effect).
Memory for Order of Items
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The position of the item must be
remembered, not the item itself.
Slot-based models – info is dropped into
a series of slots, read off in order.
Chaining models – associative links form
a chain (but items can be skipped).
Perturbation model – hierarchy of
chunks is disturbed.
More Serial Order Models
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Inhibition models – retrieval starts with the
most active, then inhibits it and goes to the
second most active, and so on…
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Inhibition prevents things just recalled from being
recalled again immediately.
Repetition blindness – people fail to see the same
word presented soon after it was first seen on a
screen.
Context-based models – order tied to context.