Prof. Greg Francis 1/6/20 - Purduegfrancis/Classes/PSY200/L14.pdf · Prof. Greg Francis 1/6/20 PSY...
Transcript of Prof. Greg Francis 1/6/20 - Purduegfrancis/Classes/PSY200/L14.pdf · Prof. Greg Francis 1/6/20 PSY...
Prof. Greg Francis 1/6/20
PSY 200: Intro. to Cognitive Psychology 1
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Two store model
PSY 200
Greg Francis
Lecture 14
Why it is difficult to win a pizza at Little Caesar�s.
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Memory● Simple view
wmemory is a container of past impressions and knowledge
wmemories can leak-out, decay away
● Not very realisticwneed to explain whymemories disappear
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Simple view● The container theory of memory does not explain, for
example,w why some memories are very long lasting (my childhood car
trips to Utah)
w why some memories are very brief (my wife asks me to take out the trash)
● We are not going to get a full theory of memory, but we can start to get an outlinew and identify some misconceptions about memory
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Ebbinghaus� experiments● First memory experiment (1885)● Measure how long it takes to learn a list of nonsense
syllables perfectlyw NOF, QAP, HOS, LEQ, FIK, MEC, KIJ, HOM, NEM, MOJ
● How long does the memory last?
● In what form does the memory last?
● How does it affect future behavior?
● Does it help relearn the list at a later time?
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Ebbinghaus
● Relearn the list at later points in time wa different list each time
● Measure how long it takes to relearn the list
● Calculate savings
Savings = Time Time
Timeoriginal relearn
original
−
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Forgetting curve● Savings =1
w subjects do not need to relearn, perfect memory
● Savings=0w subjects show no evidence of earlier learning
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0 5 10 15 20 25 30
Time (days)
Savi
ngs
Still not 0!
Prof. Greg Francis 1/6/20
PSY 200: Intro. to Cognitive Psychology 2
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Significance● Ebbinghaus� results suggest that memories can
last a very long time, in some formw Memories were believed to be �stored� in a memory
system and did not just fade away (otherwise, the curve should not asymptote above zero)
w Memory loss was believed to be due to interference of other memories
● Other experiments challenge this view
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Memory task
● See (or hear) a trigram of consonants
● Report it back in order
● Ebbinghaus� results suggest good memory until other letters are also memorized
WRM
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Retention
● Peterson & Peterson (1959)wBrown (1958)
● Give subjects trigramwask them to count backwards by 3�s and
then recall trigram
WRM 782
779, 776, 773,...
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Retention● Vary duration of counting backward
● Numbers are different from letters, you might not expect any interferencewbut they can have very strong interference
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0 3 6 9 12 15 18Retention interval (seconds)
Prop
ortio
n co
rrec
tSuggestssome memorieslast only a few seconds!
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Retention● The results of the Brown-Peterson study
suggest that some aspects of forgetting are process drivenwkeeping a memory �active� requires effort
w if you are distracted by another task, you cannot apply the effort to keep the memory
wsimilar to our observations about attention and processing
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Retention● The results of the Brown-Peterson study also
suggest that some aspects of forgetting are passivew even if you are distracted, you can recall the trigram if
only a short time has passed
w if many seconds have passed, while you are distracted, you cannot recall the trigram
w memory has �decayed�, or something like decay, while you were doing the distracting task
Prof. Greg Francis 1/6/20
PSY 200: Intro. to Cognitive Psychology 3
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Retention● CogLab data
w 85 subjects
w Not everyone shows interference on this task
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Another experiment
● Memory spanwhow many items can
you correctly recall immediately after exposure?
● �The magic number 7+/-2:…�wMiller (1956)
95 7
8 6 34 9 2 7
5 9 0 1 36 8 2 9 3 4
7 2 5 1 6 9 39 1 0 3 5 7 3 2
3 9 0 5 7 4 2 1 6
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Interpretation● There exist two types of memory systems
● Long Term Memory (LTM)w high capacity (no limit)
w long duration (forever)
w Ebbinghaus� experiment
● Short Term Memory (STM)w small capacity (~7 items)
w short duration (seconds)
w Memory span, Brown-Peterson
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Pizza● The Little Caesar�s in W. Lafayette used to
have a game where you could win a pizzaw must repeat a sequence of flashing lights
(changes every time)w The sequence gets longer until you make a
mistakew need a sequence length >7 to win much
» Counts number of correct button presses» 56 (sequence of 11 buttons): win a soft drink
» 110 (sequence of 15 buttons): win crazy bread
» 210 (sequence of 20 buttons): win pizza» nearly impossible with STM properties
w http://www.freegames.ws/games/kidsgames/simon/simon.htm
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Modal Model of Memory● Atkinson & Shiffrin (1968)
● Multiple stages of memory
● STM plays a dominant role in active memory
● Requires transfer between STM (STS) and LTM (LTS)
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Modal Model of Memory● When something is memorized
w Items are first held in STM (temporary store)
w Items may transfer to LTM (permanent store)
w Takes time to transfer
Prof. Greg Francis 1/6/20
PSY 200: Intro. to Cognitive Psychology 4
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Free Recall Serial Position Curve● Given almost any list of items
● Subjects remember the first and last few items best (free recall, not immediate serial recall)
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1 2 3 4 5 6 7Position in list
Prob
abili
ty o
f rec
all
PRIMACY
RECENCY
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Serial position curve● The effect of position is robust across many types of lists
w wordsw lettersw numbersw pictures…
● Here�s the CogLab dataw (91 subjects)
● Demo
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Serial position curve● The effect of position is robust across many types of lists
w wordsw lettersw numbersw pictures…
● Here�s the CogLab Global dataw (26,557 subjects)
● Demo
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Serial position curve
● In some situations the serial position curve can be explained by different properties of STM and LTM
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1 2 3 4 5 6 7Position in list
Prob
abili
ty o
f rec
all
PRIMACY:Use LTM
RECENCY:Use STM
NEITHER LTM NOR STM
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Conclusions
● Short Term Memory (STM)
● Long Term Memory (LTM)
● STM / LTM distinction is one of the strongest conclusions of cognitive psychology
● Accounts for quite a bit of data
● Many details are unresolved
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Next time● Expansion of STM into
● Working memoryw central executive
w phonological store
w visuo -spatial sketchpad
● CogLab on Sternberg search due!
● Why there is a gate at the first floor stairway in the Psych building.