Memory 231A sleeping mother will awake to her infant’s cries while sleeping through louder,
less important sounds such as a passing train (LaBerge, 1980).
What happens when information does pass through the selective attention
filter and into short-term memory? Short-term memory tends to be encoded pri-
marily in auditory (sound) form. That simply means that people tend to “talk”
inside their own heads. Although some images are certainly stored in STM in a
kind of visual “sketchpad” (Baddeley, 1986), auditory storage accounts for much
of short-term encoding. Even a dancer planning out moves in her head will not
only visualize the moves but also be very likely to verbally describe the moves in
her head as she plans. An artist planning a painting certainly has visual informa-
tion in STM but may also keep up an internal dialogue that is primarily auditory.
Research in which participants were asked to recall numbers and letters showed
that errors were nearly always made with numbers or letters that sounded like
the target but not with those that looked like the target word or number (Acheson
et al., 2010; Conrad & Hull, 1964).
WORKING MEMORY Some memory theorists use the term working memory as another
way of referring to short-term memory—they see no difference between the two con-
cepts. Others feel that the two systems are quite different. In this discussion, we will
use short-term memory to refer to simple storage and working memory as relating to
storage and manipulation of information (Baddeley, 2012). Short-term memory has
traditionally been thought of as a thing or a place into which information is put. As
mentioned earlier, current memory researchers prefer to think of memory in terms of
a more continuous system, where information flows from one form of representation
to another, rather than a series of "boxes." Working memory is therefore thought of
as an active system that processes the information present within short-term memory.
Working memory is thought to consist of three interrelated systems: a central executive
(a kind of “CEO” or “Big Boss”) that controls and coordinates the other two systems,
the visuospatial “sketchpad” of sorts that was mentioned earlier, and a kind of auditory
action “recorder” or phonological loop (Baddeley, 1986, 2012; Baddeley & Hitch, 1974;
Baddeley & Larsen, 2007; Engle & Kane, 2004). The central executive acts as interpreter
for both the visual and auditory information, and the visual and auditory information
are themselves contained in short-term memory. For example, when a person is reading
a book, the sketchpad will contain images of the people and events of the particular pas-
sage being read, while the recorder “plays” the dialogue in the person’s head. The cen-
tral executive helps interpret the information from both systems and pulls it all together.
In a sense, then, short-term memory can be seen as being a part of the working memory
system (Acheson et al., 2010; Bayliss et al., 2005; Colom et al., 2006; Kail & Hall, 2001).
Another way to think about short-term memory is as a desk where you do your
work. You might pull some files out of storage (permanent memory), or someone might
hand you some files (sensory input). While the files are on your desk, you can see them,
read them, and work with them (working memory). The “files” are now conscious mate-
rial and will stay that way as long as they are on the desk. Less important files may get
“thrown out” (forgotten as you fail to pay attention to them), while more important files
might get stored away (permanent memory), where they are not conscious until they are
once again retrieved—brought out of the desk.
CAPACITY: THE MAGICAL NUMBER SEVEN, OR FIVE, OR FOUR George Miller (1956)
wanted to know how much information humans can hold in short-term memory at any
one time (or how many “files” will fit on the “desk”). He reviewed several memory stud-
ies, including some using a memory test called the digit-span test, in which a series of num-
bers is read to subjects in the study who are then asked to recall the numbers in order. Each
series gets longer and longer, until the subjects cannot recall any of the numbers in order.
Each person at this gathering is involved in a conversation
with others, with dozens of such conversations going on
at the same time all around. Yet if a person in another
conversation says the name of one of the people in the
crowd, that person in the crowd will be able to selectively
attend to his or her name. This is known as the “cocktail-
party effect.”working memory
an active system that processes the
information in short-term memory.