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March 22
More about conscious perceptionOverview of Memory
March 24
Sensory Memory
March 29
Short-Term/Working Memory (Brooks expt. 1)
March 31
Long-Term Memory
April 5
NO CLASS
April 7
Long-Term Memory and False Memories (Loftus)
April 12Consciousness and “Perception without Awareness”
Subliminal Messages (Vokey and Read)
April 14
Memes (Dawkins)
Upcoming
Overview of Memory
• Atkinson-Shiffrin Model
Sensory Signals
Sensory Memory
Short-Term Memory
Long-Term Memory
ATTENTION
REHEARSAL
RETRIEVAL
“Types” of Memory
• Sensory Memory– brief ( < 1 second)– preattentive / parallel processing (very
large capacity)
Sensory Memory
Capacity
• Describe a simple experiment that could measure the capacity of “memory”
Capacity
• Describe a simple experiment that could measure the capacity of “memory”
• Briefly present some letters or digits and then ask the subject to report them– Called “whole report”
Capacity
+
Capacity
F S F EG S A UT O C G
+
Capacity
“Recall as many letters as you can”
Capacity
• George Sperling - Systematic investigation of memory capacity
– Result: subjects accurately recall 3 or 4 items
– What can you conclude from this result?
– Maybe subjects can only hold 3 or 4 items?
Capacity
• Could it be that subjects had encoded all the letters but failed to retrieve the information?
Capacity
• For example: What if they forgot the information before they could report it?– You would get the same result!
• How could you modify the experiment to measure the instantaneous capacity, before any forgetting can occur?
Capacity
• Partial Report - briefly present letters or digits and ask subject to report only some of them
“Report the letters in the row indicated by the arrow”
Capacity
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Capacity
U E S BO D W AI B V S
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Capacity
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Capacity
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Capacity
Which Letters?
Capacity
• Partial Report
• Result: subjects can recall any 3 or 4 letters that are indicated by the arrow !
Capacity
• Partial Report
• Result: subjects can recall any 3 or 4 letters that are indicated by the arrow !
• What does this mean about the capacity of memory?
Capacity
• There is some part of the perception system that stores huge amounts of information…
– in fact, if only a single letter is probed, instantaneous capacity is seen to be unlimited
Duration
• There is some part of the perception system that stores huge amounts of information…
• But for how long? How would you design an experiment to measure the duration of this high-capacity memory system?
Duration
• There is some part of the perception system that stores huge amounts of information…
• But for how long? How would you design an experiment to measure the duration of this high-capacity memory system?
• Vary the onset of the probe
Duration
• Partial Report
Probe Delay
# of letterspotentially recalled
500 ms0 ms never
0
4
10
Duration
• Partial Report
Delay
# of letters potentiallyrecalled
Interpretation:1. Information dwells in a brief storage “buffer”2. duration of storage lasts about 1/2 of one second
500 ms0 ms never
0
4
10
Iconic Memory
• a brief storage of “raw data” in the visual system
Echoic Memory
• Auditory information is stored in a similar sensory “buffer”– Echoic memory seems to last for several
seconds
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
2. Virtually unlimited capacity
Properties of Sensory Memory
1. Brief (iconic ~500ms; echoic ~2 seconds)
2. Virtually unlimited capacity
3. pre-attentive
Overview of Memory
• Atkinson-Shiffrin Model
Sensory Signals
Sensory Memory
Short-Term Memory
Long-Term Memory
ATTENTION
REHEARSAL
RETRIEVAL
Short-Term Memory
• process by which we hold information “in mind”
Short-Term Memory
• process by which we hold information “in mind”
• example: temporarily remembering a phone number
Characteristics of STM
• Duration? Capacity?
• How could one measure these parameters?
Characteristics of STM
• Limited Duration– Brown-Petersen Task:
• subject is given a trigram (e.g. C-F-W) to remember
• vocal rehearsal is prevented by counting backwards
• recall accuracy tested as a function of retention interval
Characteristics of STM
• STM decays over seconds
Characteristics of STM
• Limited Duration– Brown-Petersen Task Interpretation: rapid
loss of information in STM (over a period of seconds…much longer than sensory memory)
Characteristics of STM
• Limited Capacity– How might you measure capacity?
Characteristics of STM
• Limited Capacity– George Miller – Subject is given longer and longer lists of to-
be-remembered items (words, characters, digits)
Characteristics of STM
• Limited Capacity– George Miller – Subject is given longer and longer lists of to-
be-remembered items (words, characters, digits)
– Result: Subjects are successful up to about 7 items
Characteristics of STM
• Limited Capacity– What confound must be considered ?!
Characteristics of STM
• Limited Capacity– What confound must be considered ?!– Recalling takes time !
Characteristics of STM
• Limited Capacity– What confound must be considered ?!– Recalling takes time !– It seems that the “capacity” of STM (at least
measured in this way) depends on the rate of speech - faster speech leads to apparently larger capacity
– Some believe capacity is “2 - 3 seconds worth of speech”
Forgetting from STM
• Why do we “forget” from STM?– Does the memory trace decay?
• not likely because with very small lists (like 1 item) retention is high for long intervals
Forgetting from STM
• Why do we “forget” from STM?– Does the memory trace decay?
• not likely because with very small lists (like 1 item) retention is high for long intervals
– Instead, it seems that information “piles up” and begins to interfere
Forgetting from STM
• Interference in STM is complex and specific
Forgetting from STM
• Interference in STM is complex and specific
• For example, severity of interference depends on meaning
Forgetting from STM
• Interference in STM is complex and specific
• For example, severity of interference depends on meaning– Subjects are given successive recall tasks with
list items from the same category (e.g. fruits)– final list is of either same or different category -
how is good is recall on this list?
Forgetting from STM
• Accuracy rebounds if category changes
Coding in STM
• How is information coded in STM?
Coding in STM
• Clues about coding in STM:– # of items stored in STM depends on rate of
speech
Coding in STM
• Clues about coding in STM:– # of items stored in STM depends on rate of
speech– phonological similarity effect: similar sounding
words are harder to store/recall than different sounding words
Coding in STM
• Clues about coding in STM:– # of items stored in STM depends on rate of
speech– phonological similarity effect: similar sounding
words are harder to store/recall than different sounding words
What does this suggest about the nature of information in STM?
Coding in STM
• It seems that information can be stored in a linguistic or phonological form
Coding in STM
• It seems that information can be stored in a linguistic or phonological form
Must it be stored this way?
Coding in STM
• It is also possible to “keep in mind” non-verbal information, such as a map
Are there two different STM systems?
Read Intro and Expt. 1 in article Brooks
