forgetting and interference in short-term memory brown-peterson task
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Forgetting and Interference in Short-term memory Brown-Peterson Task Proactive Interference (PI) Release from PI Retrieval of info from STM Sternberg (1966) Task Stages Findings. Forgetting and Interference in Short-term memory Brown (1959) - PowerPoint PPT PresentationTRANSCRIPT
Forgetting and Interference in Short-term memory Brown-Peterson Task
Proactive Interference (PI)Release from PI
Retrieval of info from STMSternberg (1966)
TaskStagesFindings
Forgetting and Interference in Short-term memory
Brown (1959) Peterson and Peterson (1959) both tested a decay theory of immediate memory considered possibility of proactive interference
Task (Brown-Peterson task)
Brown-Peterson task
get 3 letters to remember
get a number (start counting backward by 3s)
recall letters when given a cue
+ + +
X S V
3 6 1
*****
+ + +
D L F
2 9 2
*****
P(r)
1.0
0.0
Proportion of Items Recalled as a Function of(Filled) Retention Interval
Retention Interval (s)
0 3 6 9 12 15 18
P(r)
1.0
0.0
Proportion of Items Recalled as a Function of(Filled) Retention Interval
Retention Interval (s)
0 3 6 9 12 15 18
P(r)
1.0
0.0
Proportion of Items Recalled as a Function of(Filled) Retention Interval
Retention Interval (s)
0 3 6 9 12 15 18
Decay orProactiveInterference?
Considered Proactive InterferenceLooked at performance for 4 blocks of trials
If PI occurred, then performance should getworse across the 4 blocks of trials
Considered Proactive InterferenceLooked at performance for 4 blocks of trials
If PI occurred, then performance should getworse across the 4 blocks of trials
Mean % Accuracy by Block
Block1 2 3 4
33 41 40 43
Considered Proactive InterferenceLooked at performance for 4 blocks of trials
If PI occurred, then performance should getworse across the 4 blocks of trials
Mean % Accuracy by Block
Block1 2 3 4
33 41 40 43
No evidence of PI; so, seems like evidence for decay(also thought retroactive interference was eliminated)
Peterson and Peterson (1959) used 2 practice trials then looked at mean performance for blocks of 12 trials
Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials
If PI occurs, then performance should get worseacross trials (the more trials, the more PI)
P(r)
1.0
0.0
Proportion of Items Recalled by Trial NumberAnd Recall Delay
Trial Number
1 2 3 4 5 6
3-s delay
18-s delay
Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials
If PI occurs, then performance should get worseacross trials (the more trials, the more PI)
Conclusion: PI occurs, builds up quickly
P(r)
1.0
0.0
Proportion of Items Recalled by Trial NumberAnd Recall Delay
Trial Number
1 2 3 4 5 6
3-s delay
18-s delay
Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials
If PI occurs, then performance should get worseacross trials (the more trials, the more PI)
Conclusion: PI occurs, builds up quicklyAlso, little forgetting without PI(evidence against decay theory)
Keppel and Underwood (1968) Maybe PI builds up quickly examined performance over first few trials
If PI occurs, then performance should get worseacross trials (the more trials, the more PI)
Conclusion: PI occurs, builds up quicklyAlso, little forgetting without PI(evidence against decay theory)
Note: distractor task is producingretroactive interference, too
Wickens (1968) obtained quick build-up of PI with different
category exemplars (e.g., examples of professions,fruits, etc.)
Manipulation – category switch continued with same category (no switch) vs.
changed to a new category (switch)
P(r)
1.0
0.0
Proportion of Items Recalled by Trial NumberAnd Recall Delay
Trial Number
1 2 3 4 5 6
professions
fruits fruit(no switch)
fruit(switch)
Wickens (1968) obtained quick build-up of PI with different
category exemplars (e.g., examples of professions,fruits, etc.)
Manipulation – category switch continued with same category (no switch) vs.
changed to a new category (switch)
Release from PI due to a shift in materialConclusion: Build-up of PI due to similar material
(interference from similar material)
Forgetting and Interference in Short-term memory Brown-Peterson Task
Proactive Interference (PI)Release from PI
Retrieval of info from STMSternberg (1966)
TaskStagesFindings
Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J)
called the memory set(the memory set size can vary)
Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J)
called the memory set(the memory set size can vary)
then get a probe (a letter): encode the probe
Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J)
called the memory set(the memory set size can vary)
then get a probe (a letter): encode the probe scan items in STM
Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J)
called the memory set(the memory set size can vary)
then get a probe (a letter): encode the probe scan items in STM make decision: Is the probe a letter in the memory set ?
Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J)
called the memory set(the memory set size can vary)
then get a probe (a letter): encode the probe scan items in STM make decision: Is the probe a letter in the memory set ? press button for yes (a positive response)
or button for no (a negative response)
Retrieval of info from STM Sternberg’s (1966) task first, get a set of letters to remember (B K V J)
called the memory set(the memory set size can vary)
then get a probe (a letter): encode the probe scan items in STM make decision: Is the probe a letter in the memory set ? press button for yes (a positive response)
or button for no (a negative response)
Collect reaction time (RT) for response
B V
V
R C
T
B V M S
S
R C G W
T
Encode probe
Scan:Compare probe to items in memory set
Decisionyes/no
Execute motor response
Encode probe
Scan:Compare probe to items in memory set
Decisionyes/no
Execute motor response
How do we scan items in STM?
Encode probe
Scan:Compare probe to items in memory set
Decisionyes/no
Execute motor response
How do we scan items in STM?
all at the same time (parallel search)?one at a time (serial search)?
RT(ms)
Reaction Time as of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
RT(ms)
Reaction Time as of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
Scan all items at once(parallel search)
RT(ms)
Reaction Time as of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
Scan items one at a time(serial search)
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
Scan items one at a time(serial search)!
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
RT = mx + b
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
RT = mx + b
m, slope of linex, # of items in mem setb, y-intercept
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
RT = mx + b
m = 38 ms (slope)x, # of items in mem setb = 397 ms (y-intercept)
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700
RT = 38x + 397
m = 38 ms (slope)x, # of items in mem setb = 397 ms (y-intercept)
Encode probe
Scan:Compare probe to items in memory set
Decisionyes/no
Execute motor response
Encode probe
Scan:Compare probe to items in memory set
Decisionyes/no
Execute motor response
Slope38 ms peritem in set
y-intercept y-intercept
Serial search
Question: Exhaustive or Self-terminating Search?
Exhaustive: Scan all the items in the memory set(no matter what)
Self-terminating: Stop scanning if a match is found
Serial search
Question: Exhaustive or Self-terminating Search?
Exhaustive: Scan all the items in the memory set(no matter what)
Self-terminating: Stop scanning if a match is found “no” vs. “yes” responses
“no” responses: must scan all items (to know probe is not in the set)
“yes” responses: could scan all items OR stop scanning if match found
Serial search -- “no” vs. “yes” responses“no” responses: must scan all items
(to know probe is not in the set)
“yes” responses: could scan all items OR stop scanning if match found
ReasoningIf the scanning is exhaustive (regardless of whether
the probe is present in the memory set) then the slopes of RT functions should be the same for “yes” and “no” responses.
If the scanning is self-terminating, then the slope of the “yes” RT function should be half that of the “no” RT function. Why? On average, the probe will occur half-way through the serial scanning.
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700Exhaustive searchprediction “No”
“Yes”
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700Self-terminating search prediction
“No”
“Yes”
RT(ms)
Reaction Time as Function of Memory Set Size
Memory Set Size
1 2 3 4 5 60
400
500
600
700Actual finding
“No”
“Yes”
Serial search
Question: Exhaustive or Self-terminating Search?
Exhaustive: Scan all the items in the memory set(no matter what)
Self-terminating: Stop scanning if a match is found
Serial search
Question: Exhaustive or Self-terminating Search?
Exhaustive: Scan all the items in the memory set(no matter what)
Seems kind of weird. Why not stop if there is a match?
Serial search Question: Exhaustive or Self-terminating Search?
Exhaustive: Scan all the items in the memory set(no matter what)
Seems kind of weird. Why not stop if there is a match?
Don’t confuse scanning stage with the decision stage.
If scanning is fast but decision is slow, then it is more efficient to scan all items, then make a single decision compared to making a decision after scanning each item (i.e., making multiple decisions).
Forgetting and Interference in Short-term memory Brown-Peterson Task
Proactive Interference (PI)Release from PI
Retrieval of info from STMSternberg (1966)
TaskStagesFindings