136 • CHAPTER 5 Short-Term and Working Memory
Most people fi nd that the pointing task is more diffi cult. The reason is that hold-
ing the image of the letter and pointing are both visuospatial tasks, so the visuospatial
sketch pad becomes overloaded. In contrast, saying “Out” or “In” is an articulatory
task that is handled by the phonological loop, so speaking didn’t interfere with visual-
izing the F.THE CENTRAL EXECUTIVE
The central executive is the component that makes working memory “working,”
because it is the control center of the working memory system. Its mission is not to
store information, but to coordinate how information is used by the phonological loop
and visuospatial sketch pad (Baddeley, 1996).
Baddeley describes the central executive as being an attention controller. It deter-
mines how attention is focused on a specifi c task, how it is divided between two tasks,
and how it is switched between tasks. The central executive is therefore essential in
situations such as the ones described in Chapter 4, when a person is attempting to
simultaneously drive and use a cell phone. In this example, the executive would be
controlling a phonological loop process (talking on the phone; understanding the con-
versation) and a sketchpad process (visualizing landmarks and the layout of the streets;
navigating the car).
One of the ways the central executive has been studied is by assessing the behavior
of patients with brain damage. As we will see later in the chapter, the frontal lobe plays
a central role in working memory. It is not surprising, therefore, that patients with
frontal lobe damage have problems controlling their attention. A typical behavior of
frontal lobe patients is perseveration—repeatedly performing the same behavior even if
it is not achieving the desired goal.
Consider, for example, 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. This persevera-
tion represents a breakdown in the central executive’s ability to control attention.
Another example of how the central executive controls attention is provided by
situations in which a person is supposed to focus attention on “relevant” stimuli and
ignore other, “irrelevant” stimuli. Some people are better at focusing attention than
others. When we describe these individual differences in the “Something to Consider”
section, we will see that these differences may be one of the reasons that some people
perform better than others on tests of comprehension and reasoning ability.THE EPISODIC BUFFER
We have seen that Baddeley’s three-component model can explain a number of results.
However, research has shown that there are some things the model can’t explain. One
of those things is that 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 126)
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.
These ideas are nothing new. It had long been known that the capacity of working
memory can be increased by chunking and that there is an interchange of information
between working memory and long-term memory. But Baddeley decided it was neces-
sary to propose an additional component of working memory to address these abilities.
This new component, which he called the episodic buffer, is shown in Baddeley’s new
model of working memory in ● Figure 5.22. The episodic buffer can store informationCopyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.