You first learned about working memory in Section 4 when we talked about the frontal lobes (see Section 4-8). In this section, you will learn more about how working memory helps us to remember and adapt to the world around us.

Working memory is an expansion of the concept of short-term memory. Research had shown that short-term memory is not simply a small store of information that is held briefly at the conscious level: information also is processed in short-term memory — often in very complex ways. According to Baddeley (1993), "Short-term memory is not a single unitary system; rather it is an amalgam[∂] or alliance of several temporary memory systems working together" (p. 39). Baddeley and Hitch (1974) named this amalgam, "working memory." Working memory is a memory subsystem that comprises a set of mental structures and processes involved in organizing and integrating sensory and other information held in the short-term store. In describing working memory, it will help first to consider some examples. In the following partial sentence, to what specific sequence of actions does the word "hit" refer?

The ball was hit by the ___?

You cannot specify the actions until you know who or what is hitting the ball. If the final word in the sentence is baby, the specific actions performed would be very different than if the final word is batter. In order to understand which actions are being performed, your short-term store needs to hold onto all the words in the sentence until the final word is spoken, at which time your working memory can integrate them.

Let's look at another (similar) example. Let's say that someone reads aloud to you the following incomplete sentence:

He strode across the court and objected to what had just occurred
because his opponent had _____.

Again, you must hold the words in your short-term store — words that cannot be fully integrated and understood until the final words are spoken. Let's say that, to complete the sentence, you are read one of the following two phrases:

• stepped across the baseline during his serve.
• presented hearsay evidence to the jury.

As you can see, each phrase would lead your working memory to give a different interpretation to the initial words of the sentence. But the sentence cannot be interpreted until all the words have been spoken, at which time your working memory integrates the information and processes its meaning.

Components of Working Memory

According to Baddeley (2004), the four main components of working memory are:

1. the central executive
2. the phonological loop
3. the visuo-spatial sketch pad
4. the episodic buffer

A. Central Executive. Please read the following passage and answer the question that immediately follows it:

There was a strange noise emanating from the dark house. Bob had to venture in to find out what was there. He was terrified: rumor had it that the house was haunted. He would feel more secure with a stick to defend himself and so he went and looked among his baseball equipment. He found a bat that was very large and brown and was flying back and forth in the gloomy room. Now he didn't need to be afraid any longer. (Baddeley, 1993, pp. 68-69)

Is the bat (a) something you hit a baseball with or (b) a flying mammal? When people read the words, "He found a bat that was very large and brown...," most would choose (a); but after reading the words, "...and was flying back and forth in the gloomy room," those with a well-functioning central executive would be much more likely to switch to (b).

The central executive is an integrated group of mental processes that monitors and coordinates all other mental functions in working memory. The central executive is analogous to the control tower at an airport: the people in the control tower monitor and coordinate all ground and air operations. In doing so, they focus their attention on the most important and demanding tasks (such as coordinating air traffic) and leave the performance of routine tasks to other personnel (such as baggage handling). Nevertheless, the people in the control tower are ready to take control of even routine tasks if a problem arises. In a similar way, the central executive attends to tasks that make the greatest cognitive demands on working memory (such as trying to memorize a word list that is being read aloud). It allows routine activities to be handled by other parts of working memory (such as recognizing that a sound made by the person reading the list is a word).

If a problem arises in one of these routine tasks, however, the central executive immediately takes control and attempts to solve it. For example, if you are driving a route that you have driven many times before, your central executive does not need to be concerned with the task and, hence, can deal with other matters. But if another car suddenly veers into your lane just a few inches in front of your bumper, your central executive takes command and figures out what needs to be done to return the situation to normal. The central executive is associated with activity in the frontal lobes of the brain (see Section 4-8 and Figure 1).

Figure 1. The right frontal lobe of the human brain (the picture appears here)

B. Phonological Loop. The word phonology refers to the relationships among the fundamental sounds used in a spoken language. The phonological loop is an integrated group of mental processes that encodes speech sounds in working memory. The influence of the phonological loop is evident in the phonemic encoding used by working memory when trying to memorize items in a word list. You probably have found that it is very difficult to listen to someone speaking to you while you also are listening to a television show. This is because the phonological loop can encode only a limited amount of speech at any one time — that is, it is limited in capacity. In fact, research on the phonological loop has shown that the capacity of the short-term store for speech sounds is limited to the number of words that one can say "subvocally" (that is, inside one's mind) in about 1.5 seconds (summarized in Baddeley, 2004). The recency effect for a list of words that is read aloud is limited to the last 1-2 words because that is all that the phonological loop can handle.

On the other hand, it is not difficult to listen to a person speaking to you while you also are listening to the "white noise" of a radio tuned to a channel with no broadcast. Research shows that the phonological loop specializes in speech sounds, although it also encodes to a lesser extent some other sounds, such as music. This makes sense when one remembers that speech itself is very musical: it exhibits intonation, pitch, and rhythm. It seems that the phonological loop is important for the learning of language and, hence, probably is an essential part of working memory during the first years of life, when language learning is at a maximum. It again becomes important when learning other languages later in life. The discovery that the phonological loop is associated with activity in areas of the temporal lobes (see Figure 2) involved in understanding and producing language is consistent with the finding that it is specialized for encoding speech sounds (see Section 4-6).

Figure 2. The right temporal lobe of the human brain (the picture appears here)

One interesting research finding is that, in fluent[∂] readers, the phonological loop does not seem to be involved in reading speed or the comprehension of written words (Baddeley, 1993). To demonstrate this to yourself, read the next few sentences while saying the word "the" under your breath. If you are a fluent reader, you should have little or no difficulty reading and understanding these sentences. If you are not a fluent reader, you probably need to subvocalize[∂] the words in order to read and understand them, as is true for beginning readers. In this case, saying the word "the" under your breath will interfere with your ability to read these sentences.

C. Visuo-Spatial Sketch Pad. In combining the words visual and spatial, Baddeley (1993) intended to refer to a part of memory that encodes visual information in terms of separate objects, as well as the arrangement of these objects in one's visual field[∂]. The visuo-spatial sketch pad is a part of working memory consisting of an integrated group of mental processes that visually encodes objects in space. For example, Wayne Gretzky, who was perhaps the greatest hockey player ever, had a unique ability to know precisely where every player was on the ice at each moment during a game. With this information, he was able to visualize a number of alternative shots and then quickly choose the best one:

What Gretzky perceives on a hockey rink is, in a curious way, more simple than what a less accomplished player perceives. He sees not so much a set of moving players as a number of situations.... Moving in on the Montreal blueline, as he was able to recall while he watched a videotape of himself, he was aware of the position of all the other players on the ice. The pattern they formed was, to him, one fact, and he reacted to that fact. When he sends a pass to what to the rest of us appears an empty space on the ice, and when a teammate magically appears in that space to collect the puck, he has in reality simply summoned up from his bank account of knowledge the fact that in a particular situation, someone is likely to be in a particular spot, and if he is not there now he will be there presently. (Gzowski, 1981; quoted in Gladwell, 1999)

Gladwell (1999) called Gretzky a "physical genius," by which he meant, in part, a person whose visuo-spatial sketch pad is vastly superior to those of most other people:

What sets physical geniuses apart from other people, then, is not merely being able to do something but knowing what to do — their capacity to pick up on subtle patterns that others generally miss. This is what we mean when we say that great athletes have a "feel" for the game, or that they "see" the court or the field or the ice in a special way. Wayne Gretzky, in a 1981 game against the St. Louis Blues, stood behind the St. Louis goal, laid the puck across the blade of his stick, then bounced it off the back of the goalie in front of him and into the net. Gretzky's genius at that moment lay in seeing a scoring possibility where no one had seen one before. "People talk about skating, puck-handling, and shooting," Gretzky told an interviewer some years later, "but the whole sport is angles and caroms, forgetting the straight direction the puck is going, calculating where it will be diverted, factoring in all the interruptions."

Those with a superior visuo-spatial sketch pad, such as Gretzky, have a distinct advantage in playing sports since rapid and accurate visual encoding is a fundamental aspect of virtually every sport.

D. Episodic Buffer. In computer terminology, a buffer is an area set aside for the temporary storage of incoming information that, when the input has been completed, is transferred elsewhere. When cognitive researchers speak of the episodic buffer, they are referring to a component of working memory that receives input from many sources, temporarily stores this information, and then integrates it in order to construct a mental episode[∂] of what is being experienced right now — a mental representation of the current moment (Baddeley, 2000; see Smith, 2004 for a summary). Baddeley (2000) described the episodic buffer as follows:

The episodic buffer is assumed to be a limited capacity [that is, it can hold only a small amount of information] temporary [several seconds] storage system that is capable of integrating information from a variety of sources. It is assumed to be controlled by the central executive, which is capable of retrieving information from the store in the form of conscious awareness, of reflecting on that information, and, where necessary, manipulating and modifying it. The buffer is episodic in the sense that it holds episodes [life events] whereby information is integrated across space and potentially extended across time. (p. 421)

It is assumed that the episodic buffer stores information in complex memory codes that consist, in part, of combinations of several simpler memory codes (such as phonemic, visual, and semantic). In addition, it is thought that the episodic buffer is the part of working memory that interacts with parts of the long-term memory subsystem (see Sections 6-10 and 6-11). The relationships among the different components of working memory, and the interaction of the episodic buffer with long-term memory, are illustrated in Figure 3.

Figure 3. Relationships among the four components of working memory

Study Questions for Section 6-8

1. How would you define working memory in your own words?
2. What are the four main components of working memory?
3. How would you define the central executive in your own words?
4. What is an example of the functioning of the central executive that is not mentioned in the readings?
5. How would you define the phonological loop in your own words?
6. What is an example of the functioning of the phonological loop that is not mentioned in the readings?
7. How is the phonological loop important for language learning and for engaging in conversations with others?
8. How would you define the visuo-spatial sketch pad in your own words?
9. What is an example of the functioning of the visuo-spatial sketch pad that is not mentioned in the readings?
10. What is meant by a "buffer" when talking about the functioning of a computer program?
11. How would you define the episodic buffer in your own words?
12. What is an example of the functioning of the episodic buffer not mentioned in the readings?

Go to Quiz 6-8 questions

Go to Readings Section 6-9