Download Sperling 1960

Primary Memory
Questions for this section
• Is there more than one kind of primary memory?
• What is the capacity of primary memory?
• What do serial position and activation effects tell us about
the nature of primary memory?
• What does rehearsal accomplish?
• How is information lost from primary memory?
• How do we retrieve information from primary memory?
Sensory Memory
• Sensory memory is responsible for initial (fast)
processing of sensory stimulation.
• Characteristics
– Preattentive and automatic.
– Info. loss occurs through decay.
• Iconic Memory
– Vision
• Echoic Memory
– Auditory
Sperling 1960
A classic experiment on iconic memory.
Subjects are presented brief displays (~50 msec) of letters such as this:
G
L
K
V
Q
H
P
B
X
N
Y
D
Whole Report: Ss are told to recall as many letters as they can.
Partial Report: Ss are cued (tone) AFTER the display is gone on which
row to recall
Logic and Results from Sperling (1960)
On average, Ss remember about 4 letters for the WR conditions, and they
remember about 3.5 letters for the PR conditions.
If we keep in mind that for WR, the 4 letters that are recalled are out of
12 possible, they only recall about 33%. However, for PR, the 3.5 letters
that are recalled are out of 4 possible… thus recall in this condition is
close to 90%.
The increased recall percentage in the PR conditions is called the Partial
Report Superiority Effect.
Of course, the questions now becomes WHY?
Sperling argued that after the offset of the stimuli, a visual “icon” was
present, and subjects recalled information from that icon.
Another twist to the Sperling (1960) experiments…
Sperling also varied the amount of time between stimulus offset and the
recall cue (tone) for the PR conditions. These data are shown below:
0
~300 msec
WR
Offset to Tone Delay
What do these data tell us?
That the icon only lasts for a very brief (~300 msec) amount of time.
Echoic Memory
• Darwin, Turvey & Crowder’s (1972) “Threeeared man” study.
– Also found a PRSE, but the duration lasted as many as
2 seconds.
• Why would echoic memory last longer than
iconic memory?
• Suffix effect.
– If recall cue is physically similar to words on a list,
recency effect disappears.
Short-term Memory
• What is it?
– IP psychologists described
it as a “place” separate from
LTM.
– Contemporary cognitive
psychologists argue that it is
simply the activated portion
of LTM.
• How much info.can it
hold?
– Depends on the content of
the information
(sometimes we can
“chunk” info.).
– Also depends on our level
of arousal (YerkesDodson Law).
Serial Position Effects
When we present info. (e.g. words) for subjects to remember, and we
then plot their accuracy as a function serial position, we will
normally see primacy and recency effects (see below).
Primacy Effect
Serial Position
Recency Effect
Explaining Primacy
Glanzer and Cunitz (1966) argued that the primacy effect occurs
because Ss are able to rehearse the items more at the beginning of
the list.
How would you test this hypothesis?
Glanzer andCunitz’s data…
No Primacy
Serial Position
Explaining Recency
Glanzer and Cunitz (1966) argued that recency effects occur because
those items at the end of the list are the most activated items.
How would you test this hypothesis?
Glanzer and Cunitz’s data
No Recency
Serial Position
Rehearsal
• Serves two purposes
in STM.
– Keeps info. active in
STM
– Gets info. from STM
to LTM for later
retrieval.
• Craik and Lockheart
(1972)
– Maintenance rehearsal
• Keeps info. active in
STM.
– Elaborative rehearsal
• Helps create LTM trace
for later retrieval.
• How could you test these
assumptions?
Information Loss from STM
• Peterson and Peterson (1959)
• Presented subjects with consonant-vowelconsonant (CVC) trigrams to remember for a
short period of time.
• While trying to remember, they also had to count
backwards by threes from a random number.
• Example…
FOV
893
RECALL
Peterson and Peterson’s (1959) data
P & P demonstrated that the DURATION of STM was not very
long. That is, if information is not rehearsed, it does not stay in
STM for more than a few seconds
After 3 secs.,
Accuracy is ~50%
After 15 secs.,
Acc is ~10%
0
3
15
Delay (seconds)
Explaining Loss from STM
• Peterson and Peterson argued for a decay
explanation of their data.
• Keppel and Underwood (1962) argued that the P
& P data were due to proactive interference.
– When items at the beginning of the experiment
interfere with memory for the items at the end of the
experiment.
Retrieval from STM
• Another important question we may ask is
how we get the information out of STM…
that is, how do we retrieve it?
• Sternberg (1966) performed a classic study
to answer this question.
Sternberg (1966)
In this study, Ss were presented w/ “memory sets” that varied from
1 – 6 letters. After presentation of the memory set a “target”
letter was presented. Ss had to respond as quickly and as
accurately as they could whether or not the target was a member
of the previous memory set.
Two questions regarding retrieval emerge:
1. Is STM retrieval a parallel or serial process?
2. Is STM retrieval a self-terminating or exhaustive process?
Reaction Time
Sternberg’s (1966) data…
“No”
“Yes”
1
6
Do these data indicate that search is parallel or serial? Selfterminating or exhaustive? WHY?
An alternative account of Sternbergs’ data…
These very data can be explained by a parallel search… how?
If we assume that activation is limited and that each item in the
memory set needs some activation to remain in STM, then items in
the larger memory sets receive proportionately less activation that
items in the smaller set.
A parallel search that depends on the activation level of each item
can explain these data very well.