Short-Term and Working Memory

CHAPTER 5: SHORT-TERM AND WORKING 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 Sensory memory  When something is presented briefly, such as a face illuminated by a flash, your perception continuous for fraction of a second in the dark  This brief persistence of the image, which is one of the things that make it possible to perceive movies 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 Long-term memory  Responsible for storing information for long periods of time which can extend from minutes to lifetime A.) episodic memories - long term memories of experiences from the past B.) Procedural memory - the ability to ride or do any other things that involve muscle coordination Semantic memory  Memories of facts such as an address or a birthday of the names of different objects (that’s a bicycle) The Model of Memory  By Richard Atkinson and Richard Shiffrin  It proposed three types of memory 1. Sensory memory - is an initial stage that holds incoming information for seconds or fractions of a second 2. Short-term memory (STM) - holds five to seven items for about 15 to 20 seconds 3. Long-term memory (LTM) - can hold a large amount of information for years or even decades  They are called structural features  They also proposed control process which are dynamic process associated with the structural features that can be controlled by the person and may differ from one task or another  An example of control process that operates on short-term memory is rehearsal—repeating a stimulus over and over, as you might repeat a telephone in order to hold it in your mind  Other examples: relating digits in number to familiar date or history, Illustration how structural features and control processes operate Encoding  The process of storing the number in long-term memory Retrieval  The process of remembering information that is stored in long-term memory SENSORY MEMORY  The retention, for briefs period of time, of the effects of sensory stimulation  Ex: trail left by a moving sparkler and the experience of seeing a film Although it appears that this trail is created by light left by the sparkler as you wave it through the air, there is, in fact, no light along this trail. The lighted trail is a creation of your mind, which retains a perception of the sparkler’s light for a fraction of a second Persistence of vision  is the continued perception of a visual stimulus even after it is no longer present.  This persistence lasts for only a fraction of a second  the persistence of vision effect is noticeable for brief stimuli, like the moving sparkler Ex: Watching a movie - a person viewing the film doesn’t see the dark intervals between the images because the persistence of vision fills in the darkness by retaining the image of the previous frame.  Sperling’s Experiment: Measuring the Capacity and Duration of the Sensory Store George Sperling (1960)  wondered how much information people can take in from briefly presented stimuli.  . He determined this in a famous experiment in which he flashed an array of letters and asked his participants to report as many of the letters as possible. Whole report method  participants were asked to report as many letters as possible from the entire 12-letter display Conclusion: Because the exposure was brief, participants saw only an average of 4.5 of the 12 letters.  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 letter Partial report method  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 Delayed partial report method  the letters were flashed on and off and then the cue tone was presented after a short delay Sperling conclusion:  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. Iconic memory or visual icon  brief sensory memory for visual stimuli which corresponds to the sensory memory stage of Atkinson and Shiffrin’s modal model. Echoic memory  Persistence of sound lasts for a few seconds after presentation of the original stimulus Ex: 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. Short-Term Memory: Storage  the system involved in storing small amounts of information for a brief period of time  Thus, whatever you are thinking about right now, or remember from what you have just read, is in your short-term memory  Everything we think about or know at a particular moment in time involves STM because short-term memory is our window on the present 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. What Is the Duration of Short-Term Memory?  Last for 15 to 20 seconds demonstrated by John Brown, Lloyd Peterson and Margaret Peterson  They used the method of recall to determine the duration of STM. Exp: 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. Findings: 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 second How Many Items Can Be Held in Short-Term Memory? Digit span  the number of digits a person can remember  the average capacity of STM is about five to nine items—about the length of a phone number.  By George Miller Change Detection  set the limit at about four items  By by Steven Luck and Edward Vogel (1997) Finding: performance 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  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. CHUNKING  to describe the fact that small units (like words) can be combined into larger meaningful units, like phrases, or even larger units, like sentences, paragraphs, or stories Ex: monkey, child, wildly, zoo, jumped, city, ringtail, young >> : ringtail monkey, jumped wildly, young child, city zoo. Chunk    a collection of elements that are strongly associated with one another but are weakly associated with elements in other chunks the word ringtail is strongly associated with the word monkey but is not as strongly associated with the other words, such as child or city chunking in terms of meaning increases our ability to hold information in STM. K. Anders Ericsson and coworkers (1980)  demonstrated an effect of chunking by showing how a college student with average memory ability was able to achieve amazing feats of memory  he was able to repeat sequences of up to 79 digits without error  S.F. used chunking to recode the digits into larger units that formed meaningful sequences Ex: 3,492 became “3 minutes and 49 points 2 seconds, near world-record mile time.”  Chunking enables the limited-capacity STM system to deal with the large amount of information involved in many of the tasks we perform every day How Much Information Can Be Held in Short-Term Memory?  Rather than describing memory capacity in terms of “number of items,” it should be described in terms of “amount of information  We can understand the reasoning behind the idea that information is important by considering storing pictures on a computer flash drive. The number of pictures that can be stored depends on the size of the drive and on the size of the pictures George Alvarez and Patrick Cavanagh (2004)  did an experiment using Luck and Vogel’s change detection procedure but, they also used more complex objects Findings: Participants’ ability to make the same/different judgment depended on the complexity of the stimuli.  The greater the amount of information in an image, the fewer items that can be held in visual short-term memory Should short-term memory capacity be measured in terms of “number of items” or “amount of detailed information?  both ideas, and the discussion among researchers is continuing.  we could compare it to a container like a leaky bucket that can hold a certain amount of water for a limited amount of time Working Memory: Manipulating Information Working memory  “a limited-capacity system for temporary storage and manipulation of information for complex tasks such as comprehension, learning, and reasoning.”  Ex: remembering numbers while reading a paragraph  There are other ways to carry out this calculation, but whatever method you choose involves both holding information in memory and processing information  The fact that STM and the modal model do not consider dynamic processes that unfold over time is what led Baddeley and Hitch to propose that the name working memory, rather than short-term memory, be used for the short-term memory process Baddeley  one of the things he noticed was that under certain conditions it is possible to carry out two tasks simultaneously  participants were able to read while simultaneously remembering numbers.  working memory must be dynamic and must also consist of a number of components that can function separately Baddeley’s working memory model 1. Phonological loop - holds verbal and auditory information Ex: when you are trying to remember a telephone number or a person’s name a.) phonological store - a limited capacity and holds information for only a few seconds b.) articulatory rehearsal process -responsible for rehearsal that can keep items in the phonological store from decaying 2. Visuospatial sketch pad - holds visual and spatial information Ex: finding your way around campus 3. central executive - is where the major work of working memory occurs.  pulls information from long-term memory and coordinates the activity of the phonological loop and visuospatial sketch pad by focusing on specific parts of a task and deciding how to divide attention between different tasks.  “Traffic cop” = coordinating and combining these two kinds of information The Phonological Loop phonological similarity effect  is the confusion of letters or words that sound similar  For example: “F” was most often misidentified as “S” or “X,” two letters that sound similar to “F,” but was not as likely to be confused with letters like “E,”  Even though the participants saw the letters, the mistakes they made were based on the letters’ sounds word length effect  occurs when memory for lists of words is better for short words than for long words  List 1: beast, bronze, wife, golf, inn, limp, dirt, star  List 2: alcohol, property, amplifier, officer, gallery, mosquito, orchestra, bricklayer Articulatory Suppression  when a person is prevented from rehearsing items to be remembered by repeating an irrelevant sound, such as “the, the, the .  This repetition of an irrelevant sound results in a phenomenon, which reduces memory because speaking interferes with rehearsal.  repeating “the, the, the ...” not only reduces the ability to remember a list of words, it also eliminates the word length effect The Visuospatial Sketch Pad  handles visual and spatial information  involved in the process of visual imagery—the creation of visual images in the mind in the absence of a physical visual stimulus. Shepard and Metzler  inferred that participants were solving the problem by rotating an image of one of the objects in their mind, a phenomenon called mental rotation.  This mental rotation is an example of the operation of the visuospatial sketch pad because it involves visual rotation through space. The Central Executive  component that makes working memory “work,” because it is the control center of the working memory system not to store information but to coordinate how information is used by the phonological loop and visuospatial sketch pad  “Attention controller” - how attention is focused on a specific task, how it is divided between two tasks, and how it is switched between tasks  Related executive attention Perseveration  One of the ways the central executive has been studied is by assessing the behavior of patients with brain damage  repeatedly performing the same action or thought even if it is not achieving the desired goal  Ex: a problem that can be easily solved by following a particular rule (“Pick the red object”). A person with frontal lobe damage might be responding correctly on each trial, as long as the rule stays the same. However, when the rule is switched (“Now pick the blue object”), the person continues following the old rule, even when given feedback that his or her responding is now incorrect.  An Added Component: The Episodic Buffer  working memory can hold more than would be expected based on just the phonological loop or visuospatial sketch pad. For example, people can remember long sentences consisting of as many as 15 to 20 words.  The ability to do this is related to chunking, in which meaningful units are grouped together (page 140), and it is also related to long-term memory, which is involved in knowing the meanings of words in the sentence and in relating parts of the sentence to each other based on the rules of grammar. Episodic buffer  can store information (thereby providing extra capacity) and is connected to LTM (thereby making interchange between working memory and LTM possible). The Effect of Damage to the Prefrontal Cortex  The classic example of PFC damage causing changes in behavior is the case of Phineas Gage and the tamping rod        Gage survived, but reports from the time noted that the accident had changed Gage’s personality from an upstanding citizen to a person with low impulse control, poor ability to plan, and poor social skills Frontal lobes are involved in a variety of mental functions, including personality and planning. damage to the frontal lobe causes problems in controlling attention, which is an important function of the central executive. An example of animal research that explored the effect of frontal lobe damage on memory tested monkeys using the delayed-response task, which required a monkey to hold information in working memory during a delay period Monkeys can be trained to accomplish this task. However, if their PFC is removed, their performance drops to chance level, so they pick the correct food well only about half of the time. PFC is important for holding information for brief periods of time. it has been suggested that one reason we can describe the memory behavior of very young infants as “out of sight, out of mind” (when an object that the infant can see is then hidden from view, the infant behaves as if the object no longer exists) Prefrontal Neurons That Hold Information  An important characteristic of memory is that it involves delay or waiting Shintaro Funahashi and coworkers (1989)  conducted an experiment in which they recorded from neurons in a monkey’s PFC while the monkey carried out a delayed-response task.  The key result of this experiment was that Funahashi found neurons that responded only when the square was flashed in a particular location and that these neurons continued responding during the delay.  The firing of these neurons indicates that an object was presented at a particular place, and this information about the object’s location remains available for as long as these neurons continue firing The Neural Dynamics of Working Memory Mark Stokes (2015)  Proposed that information can be stored by short-term changes in neural networks activity state  in which information to be remembered causes a number of neurons, indicated by the dark circles, to briefly fire  This firing doesn’t continue, but causes the synaptic state  in which a number of connections between neurons, indicated by the darker lines, are strengthened activity-silent working memory  e changes in connectivity, last only a few seconds, but that is long enough for working memory.  Finally, when the memory is being retrieved, the memory is indicated by the pattern of firing in the network, shown by the dark circles  In Stokes’s model, information is held in memory not by continuous nerve firing but by a brief change in the connectivity of neurons in a network  Another current idea about working memory is that it involves physiological processes that extend beyond the PFC Working memory, therefore, involves an interplay between a number of areas of the brain. This interplay is symbolized by the interaction between brain areas in Figure 5.24, which depicts a network based on the research on a large number of experiments  Is working memory the same in different people?  The answer to this question—that there are individual differences in the capacity of people’s working memory—shouldn’t be surprising Meredyth Daneman and Patricia Carpenter (1980) carried out one of the early experiments on individual differences in working memory capacity by developing a test for working memory capacity and then determining how individual differences were related to reading comprehension. T  Reading span test - required participants to read a series of 13- to 16-word sentences Reading span  was the number of sentences they could read, and then correctly remember all of the last words  working memory capacity is a crucial source of individual differences in reading comprehension But what is it about differences in working memory capacity that results in these outcomes?  Edmund Vogel and coworkers (2005) focused on one component of working memory: the control of attention by the central executive  Participants in the high-capacity group were able to hold a number of items in working memory; participants in the low-capacity group were able to hold fewer items in working memory event-related potential  was measured, which indicated how much space was used in working memory as they carried out the task. Cognitive control  as a set of functions, which allow people to regulate their behavior and attentional resources, and to resist the temptation to give in to impulses  People with poor cognitive control are more easily distracted and are more likely to let these distractions interfere with ongoing behavior.  that they have difficulty dealing with temptation. 