chapter five: short-term memory and working memory Flashcards
chapter 5: short-term and working memory
memory
2 definitions of memory
➤ Memory is the process involved in retaining, retrieving, and using information about stimuli, images, events, ideas, and skills after the original information is no longer present.
➤ Memory is active any time some past experience has an effect on the way you think or behave now or in the future ( Joordens, 2011).
short term memory
The purpose of short-term memory will become clearer as we describe its characteristics, but stop for a moment and answer this question: What are you aware of right now? Some material you are reading about memory? Your surroundings? Noise in the background? Whatever your answer, you are describing what is in short-term memory. Everything you know or think about at each moment in time is in short-term memory. Thirty seconds from now your “old” short-term memories may have faded, but new ones will have taken over. Your “to do” list in long-term memory may be important, but as you are doing each of the things on your list, you are constantly using your short-term memory. As you will see in this chapter, short-term memory may be short in duration, but it looms large in importance.
Short-term memory (STM) is the system involved in storing small amounts of information for a brief period of time (Baddeley et al., 2009). Thus, whatever you are thinking about right now, or remember from what you have just read, is in your short-term memory. As we will see below, most of this information is eventually lost, and only some of it reaches the more permanent store of long-term memory (LTM).
Because of the brief duration of STM, it is easy to downplay its importance com- pared to LTM, but, as we will see, STM is responsible for a great deal of our mental life. Everything we think about or know at a particular moment in time involves STM because short-term memory is our window on the present.
memory
Sensory memory
Short-term memory
Long-term memory
1) Explicit/declarative memory: conscious recollections
- episodic memory = specific events
- semantic memory = general knowledge/facts
2) Implicit memory/nondeclarative memory: no conscious recollections
- procedural memory = actions/skills
five types of memory
1) sensory memory
- brief
- When something is presented briefly, such as a face illuminated by a flash, your perception continues for a fraction of a second in the dark. This brief persistence of the image, which is one of the things that makes it possible to perceive movies, is called sensory memory.
2) short term memory or working memory
- Information that stays in our memory for brief periods, about 10 to 15 seconds if we don’t repeat it over and over
3) long term memory
- long-term memory is responsible for storing information for long periods of time— which can extend from minutes to a lifetime.
- Long-term memories of experiences from the past, like the picnic, are episodic memories.
- The ability to ride a bicycle, or do any of the other things that involve muscle coordination, is a type of long-term memory called procedural memory.
4) semantic memory: Another type of long-term memory is semantic memory—memories of facts such as an address or a birthday or the names of different objects (“that’s a bicycle”).
the modal model of memory
Atkinson and Shiffrin
figure 5.2
this model proposed three types of memory:
structural feautures of the midel:
1) Sensory memory is an initial stage that holds all incom- ing information for seconds or fractions of a second.
2) Short-term memory (STM) holds five to seven items for about 15 to 20 seconds. We will describe the charac- teristics of short-term memory in this chapter.
3) Long-term memory (LTM) can hold a large amount of information for years or even decades.
notes:
Atkinson and Shiffrin generated a flow diagram for memory known as the modal model of memory
the modal model of memory has three structural features sensory memory/ short-term memory and long term memory /
stimuli enter sensory memory that can hold information very briefly
while it can hold a very large amount of information it’s thought that it’s not unlimited in its capacity that there is some limit to how much can enter but how much it’s not quite clear what that capacity is
information can then enter short term memory which holds approximately 5 to 7 items for 15 to 20 seconds without rehearsal
if you rehearse the information for instance you repeat it to yourself over and over again you can keep that information in short-term memory much longer
their other control process is besides that rote rehearsal of repeating something over and over again and such as directed attention, decisions, retrieval strategies or even elaborate rehearsal and coding information so that it can transfer to long term memory
output refers to a response or action based on the processing of information in short term memory and long term memory can hold what people consider to be an unlimited amount of information and the duration of which is also thought to be unlimited that is it can last possibly a lifetime
see textbook for more deets
sensory memory
Sensory memory is the retention, for brief periods of time, of the effects of sensory stimulation. We can demonstrate this brief retention for the effects of visual stimula- tion with two familiar examples: the trail left by a moving sparkler and the experience of seeing a film.
Sensory Memory: limited but large number of unanalyzed stimuli held very briefly. Explains persistence of vision
- persistence of vision: continued perception of visual stimulus after it’s no
longer present (e.g., sparkler’s trail) - this persistence lasts for only a fraction of a second, so it isn’t obvious in everyday experience when objects are present for long periods. However, the persistence of vision effect is noticeable for brief stimuli, like the moving sparkler or rapidly flashed pictures in a movie theater.
- iconic memory (visual) = .25-.50 seconds
- echoic memory (auditory) = 1-3 seconds
(sensory memory)
sperling’s experiment: measuring the capacity and duration of the sensory store
ppt notes
purpose of the Whole report method: How many letters can one report?
purpose of the Partial report method: Do participants see all letters but can’t report
them because visual trace quickly fades?
purpose of the Delayed partial report method:
How quickly does the visual trace fade?
notes:
Spearman’s Report method involved the brief presentation of an array of letters. participants would be instructed to recall as many other letters that they could
results indicated that on average 4 and a half letters could be recalled out of the 12
however some participants would report that they saw all of the letters but just forgot them before they could report them
so Sperling conducted what’s called the partial report method. the array would be presented briefly and then a tone that was either high medium or low pitch would indicate which row they would need to report
Sperling found that they could report 3.3 out of the four letters in that row which meant that they indeed must have seen about 9 letters out of the 12 but their memory trace faded as they were reporting the letters
the delayed partial report method was conducted to determine the speed at which the visual trace decayed it appeared that anything more than one set at one second delay resulted in decay indicating that the visual memory trace lasted at most for one second
sperling’s experiment: measuring the capacity and duration of the sensory store
textbook notes / whole report method
George Sperling (1960) wondered how much information people can take in from briefly presented stimuli
- He determined this in a famous experi- ment in which he flashed an array of letters, like the one in Figure 5.5a, on the screen for 50 milliseconds (50/1000 second) and asked his participants to report as many of the letters as possible.
This part of the experiment used the whole report method; that is, participants were asked to report as many letters as possible from the entire 12-letter display. Given this task, they were able to report an average of 4.5 out of the 12 letters.
At this point, Sperling could have concluded that because the exposure was brief, par- ticipants saw only an average of 4.5 of the 12 letters. However, some of the participants in Sperling’s experiment reported that they had seen all the letters, but that their perception had faded rapidly as they were reporting the letters, so by the time they had reported 4 or 5 letters, they could no longer see or remember the other letters.
perling reasoned that if participants couldn’t report the 12-letter display because of fading, perhaps they would do better if they were told to just report the letters in a single 4-letter row. Sperling devised the partial report method to test this idea
sperling’s experiment: measuring the capacity and duration of the sensory store
textbook notes / partial report method
Sperling reasoned that if participants couldn’t report the 12-letter display because of fading, perhaps they would do better if they were told to just report the letters in a single 4-letter row. Sperling devised the partial report method to test this idea. Participants saw the 12-letter display for 50 ms, as before, but immediately after it was flashed, they heard a tone that told them which row of the matrix to report. A high-pitched tone indicated the top row; a medium-pitch indicated the middle row; and a low-pitch indicated the bottom row (Figure 5.5b).
Because the tones were presented immediately after the letters were turned off, the par- ticipant’s attention was directed not to the actual letters, which were no longer present, but to whatever trace remained in the participant’s mind after the letters were turned off. When the participants focused their attention on one of the rows, they correctly reported an average of about 3.3 of the 4 letters (82 percent) in that row. Because this occurred no mat- ter which row they were reporting, Sperling concluded that immediately after the 12-letter display was presented, participants saw an average of 82 percent of all of the letters but were not able to report all of these letters because they rapidly faded as the initial letters were being reported.
sperling’s experiment: measuring the capacity and duration of the sensory store
textbook notes / delayed partial method
Sperling then did an additional experiment to determine the time course of this fad- ing. For this experiment, Sperling devised a delayed partial report method in which the letters were flashed on and off and then the cue tone was presented after a short delay (Figure 5.5c). The result of the delayed partial report experiments was that when the cue tones were delayed for 1 second after the flash, participants were able to report only slightly more than 1 letter in a row. Figure 5.6 plots this result, showing the percentage of letters available to the participants from the entire display as a function of time following presen- tation of the display. This graph indicates that 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.
Sperling concluded from these results that 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. This brief sensory memory for visual stimuli, called iconic memory or the visual icon (icon means “image”), corresponds to the sensory memory stage of Atkinson and Shiffrin’s modal model. Other research using auditory stimuli has shown that sounds also persist in the mind. This persistence of sound, called echoic memory, lasts for a few seconds after presentation of the original stimulus (Darwin et al., 1972). An exam- ple of echoic memory is when you hear someone say something, but you don’t understand at first and say “What?” But even before the person can repeat what was said, you “hear” it in your mind. If that has happened to you, you’ve experienced echoic memory. In the next section, we consider the second stage of the modal model, short-term memory, which also holds information briefly, but for much longer than sensory memory.
We saw in the preceding section that although sensory memory fades rapidly, Sperling’s par- ticipants could report some of the letters. These letters are the part of the stimuli that has moved on to short-term memory in the flow diagram in Figure 5.2.
short term memory method: recall
Most of the experiments we will be describing in this chapter involve recall, in which participants are presented with stimuli and then, after a delay, are asked to report back as many of the stimuli as possible.
Memory performance can be measured as a percentage of the stimuli that are remembered. (For example, studying a list of 10 words and later recalling 3 of them is 30 percent recall.) Participants’ responses can also be analyzed to determine whether there is a pattern to the way items are recalled. (For example, if participants are given a list consisting of types of fruits and models of cars, their recall can be analyzed to determine whether they grouped cars together and fruits together as they were recalling them.) Recall is also involved when a person is asked to recollect life events, such as graduating from high school, or to recall facts they have learned, such as the capital of Nebraska.
what is the duration of short-term memory?
One of the major misconceptions about short-term memory is that it lasts for a rel- atively long time.
It is not uncommon for people to refer to events they remember from a few days or weeks ago as being remembered from short-term memory.
However, short-term memory, as conceived by cognitive psychologists, lasts 15 to 20 seconds or less
This was demonstrated by John Brown (1958) in England and Lloyd Peterson and Margaret Peterson (1959) in the United States, who used the method of recall to de- termine the duration of STM. Peterson and Peterson presented participants with three letters, such as FZL or BHM, followed by a number, such as 403. Participants were instructed to begin counting backwards by threes from that number. This was done to keep participants from rehearsing the letters. After intervals ranging from 3 to 18 sec- onds, participants were asked to recall the three letters. Participants correctly recalled about 80 percent of the three letter groups when they had counted for only 3 seconds, but recalled only about 12 percent of the groups after counting for 18 seconds. Results such as this have led to the conclusion that the effective duration of STM (when re- hearsal is prevented, as occurred when counting backwards) is about 15 to 20 seconds or less (Zhang & Luck, 2009).
short-term memory
Short-Term Memory: limited amount of analyzed stimuli is held for 15-20
seconds unless one engages in rote rehearsal.
- Rote rehearsal is the repeating information to oneself.
- Capacity is limited
how many items can be held in short-term memory?
Not only is information lost rapidly from STM, but there is a limit to how much informa- tion can be held there. As we will see, estimates for how many items can be held in STM range from four to nine.
digit span
One measure of the capacity of STM is provided by the digit span—the number of digits a person can remember.
Digit Span studies indicate 5-9 items can be held (about the lenght of a phone number)
- Present strings of items and ask participants to recall as many as they can.
- Number of items pronounced in 1.5 – 2.0 seconds is your digit span
(Baddeley et al., 1975).
how many items can be held in short-term memory?
change detection
Change Detection studies indicate 4 items can be held (Luck & Vogel, 1997)
More recent measures of STM capacity have set the limit at about four items (Cowan, 2001). This conclusion is based on the results of experiments like one by Steven Luck and Edward Vogel (1997), which measured the capacity of STM by using a procedure called change detection.
The result of Luck and Vogel’s experiment, shown in Figure 5.8, indicates that per- formance was almost perfect when there were one to three squares in the arrays, but that performance began decreasing when there were four or more squares. Luck and Vogel con- cluded from this result that participants were able to retain about four items in their short- term memory. Other experiments, using verbal materials, have come to the same conclusion (Cowan, 2001).
These estimates of either four or five times to nine items set rather low limits on the capacity of STM. If our ability to hold items in memory is so limited, how is it possible to hold many more items in memory in some situations, as when words are arranged in a sentence? The answer to this question was proposed by George Miller, who introduced the idea of chunking in his “Seven, Plus or Minus Two” paper.
how many items can be held in short-term memory?
miller (1956) chunking
Miller (1956) proposed 7+/2 chunks of information can be held
see image
short-term memory
Change Detection Study with Complex Stimuli
Change Detection Study with Complex Stimuli (Alvarez & Cavanagh,
2004) indicates that capacity determined by amount of information. Greater
capacity for low information stimuli than high information stimuli.
working memory
Working Memory: stores and manipulates information for action (learning,
completion of tasks, reasoning).
see baddely’s working memory model
The working memory model of baddeley is similar to short-term memory often the two terms short term memory and working memory are used interchangeably but they do differ in what they are able to explain
while both short term and working memory discuss the temporary storage of information the working memory model is used to explain the manipulation of information in this temporary store working memory model consists of a central executive that directs attention an coordinates between the visual spatial sketchpad which stores visual information and a phonological cloop that stores auditory stimuli
working memory
phonological loop
A. Phonological loop:
- Phonological store that holds verbal and auditory stimuli for a few seconds
- Articulatory rehearsal process that maintains stimuli in the phonological store via
rehearsal.
B. Visuospatial Sketch Pad: holds visual and spatial information.
A. Central Executive: retrieves information from LTM (long term memory), coordinates activity in thephonological loop and visuospatial sketch pad based on task demands bydirecting attention
