Chapter 5 short term and working memory
Richard Atkinson and Richard Shiffrin (1968): Modal model of memory: included many
features of memory models that were being proposed in 1960s. stages in the model are called
structure features of the model.
o Sensory memory: initial stage that holds all incoming information for
seconds or fractions of a second
o Short term memory (STM): holds 5-7 items for about 15-30 secs
o Long term memory (LTM): hold large amount of information for years
or even decades
Control processes: active processes that can be controlled by the person and may differ
from one task to another
Rehearsal: repeating a stimulus over and over
Encoding: process of storing information in long term memory
Retrieval: process of remembering information that is stored in long term memory
Long term memory is essential for storing information but before we can become aware of
this stored information, it must be moved back into STM
Sensory memory: the retention for brief periods of time, of the effects of sensory
Persistence of vision: retention of the perception of light in your mind
George Sperling: how much information people can take in from briefly presented stimuli.
Experiment which he flashed an array of letters on the screen for 50 milliseconds and asked
his participants to report as many of the letters as possible – whole report method:
participants asked to report as many letters as possible from the whole matrix. Results:
average 4.5 out of 12 letters. Conclusion: exposure was brief, participants saw only an
average of 4.5 letters or it might be that perception faded rapidly as they were reporting the
letters, therefore no time to see the other letters in the matric
Partial report method: determine which of these two possibilities is correct. He flashed
matrix for 50ms, but immediately after it was flashed, he sounded on of the following cue
tones to indicate which row of letters the participants were to report. Cues directed
participants to focus their attention on one of the rows, they correctly reported an average of
3.3 out of 4 letters
Concluded: correct description of what was happening was that immediately after the display
was presented, participants saw an average of 82 percent of the letters in the whole display
but were not able to report all of these letters because they rapidly faded as the initial letters
were being reported
Delayed partial report method: additional experiment to determine the time course of this
fading. Presentation of cue tones was delayed for a fraction of a second after the letters were
cue tones delayed for 1 sec, able to report only slightly more than 1 letter in a row.
Immediately after a stimulus is presented, all or most of the stimulus is available for
perception. This is sensory memory.
Then over the next second, sensory memory fades until by 1 second, the number of letters is
about the same as the numbers of letters that were reported using the whole report method.
Conclusion: iconic memory/visual icon: a short lived sensory memory registers all or most
of the information that hits our visual receptors but that this information decays within less
than a second.
Echoic memory: auditory stimuli shown than sounds also persist in the mind. Lasts for a few
seconds after presentation of the original stimulus Chapter 5 short term and working memory
Sensory memory can register huge amounts of information but it retains this information for
only seconds or fractions of a second
Short term memory (STM): system involved in storing small amounts of information for a
brief period of time. Most information is eventually lost, only some of it reaches the LTM.
Recall tests: participants are presented with stimuli and then after a delay are asked to
remember as many of the stimuli as possible.
Peterson and Peterson: Memory performance can be measured as a percentage of the
stimuli that are remembered
Recall contrasts with measuring recognition, people are asked to pick an item they have
previously seen or heard from a number of other items that they have not seen or heard,
Keppel and Underwood suggested that the drop-off in memory was not due to decay of the
memory trace but to proactive interference (PI)- interference that occurs when
information that was learned previously interferes with learning new information
E.g. old number interfere with new number
Interference is happening constantly as one event follows the next and as we pay attention to
one thing after another
Outcome of this constant interference is that the effective duration of STM, when rehearsal is
prevents is about 15-20 secs.
Digit span: George miller: number of digits a person can remember. Typical span is 5-8
Average capacity of STM is about 5-9 items about the length of a phone number.
Chunking: small units can be combined into larger meaningful units like phrases, or even
larger units like sentences, paragraphs or stories. Chunking increases our ability to hold
information in STM. Making it more meaningful can become more strongly associated with
one another increases the memory span
Chunking enables the limited capacity STM system to deal with the large amount of
information involved in many of the tasks we perform everyday.
Coding: the way information is represented
Physiological approach to coding: determining how a stimulus is represented by the firing
of a number of neurons
Mental approach to coding: asking how a stimulus or an experience is represented in the
Auditory coding: representing items in STM based on their sound
Conrads: participants saw a number of target letters flashed briefly on a screen and were
told to write down the letters in the order they were presented. Participants made errors
they were most likely to misidentify the target letter as another letter that sounded like the
target. Conclusion: the code for STM is auditory rather than visual. We usually remember
them by repeating their sound over and over again
Visual coding: representing items visually, as would occur when remembering the details of
a floor plan or the layout of streets on a map. Presented participants with patterns ranging
from small to large with half of the squares being shaded in each pattern. Results:
participants able to complete patterns consisting of an average of 9 shaded squares before
making mistakes. Conclusion: possible to remember the patters shows visual coding.
Combining individual squares into sub patterns. Chunking- increase number of squares
remembered Chapter 5 short term and working memory
Semantic coding: representing items in terms of their meaning (wickens)- fruits and