230 CHAPTER 6
Echoic memory’s capacity is limited to what can be heard at any one moment
and is smaller than the capacity of iconic memory, although it lasts longer—about 2–4
seconds (Schweickert, 1993).
Echoic memory is very useful when a person wants to have meaningful conversa-
tions with others. It allows the person to remember what someone said just long enough
to recognize the meaning of a phrase. As with iconic memory, it also allows people to
hold on to incoming auditory information long enough for the lower brain centers to
determine whether processing by higher brain centers is needed. It is echoic memory that
allows a musician to tune a musical instrument, for example. The memory of the tuning
fork’s tone lingers in echoic memory long enough for the person doing the tuning to
match that tone on the instrument.What happens if the lower brain centers send the information on
to the higher centers?Short-Term Memory
6.4 Describe short-term memory, and differentiate it from working memory.
If an incoming sensory message is important enough to enter consciousness, that mes-
sage will move from sensory memory to the next process of memory, called short-term
memory (STM). Unlike sensory memory, short-term memories may be held for up to
30 seconds and possibly longer through maintenance rehearsal.
SELECTIVE ATTENTION: HOW INFORMATION ENTERS Selective attention is the abil-
ity to focus on only one stimulus from among all sensory input (Broadbent, 1958). It
is through selective attention that information enters our STM system. In Dr. Donald
E. Broadbent’s original filter theory, a kind of “bottleneck” occurs between the pro-
cesses of sensory memory and short-term memory. Only a stimulus that is “important”
enough (determined by a kind of “pre-analysis” accomplished by the attention centers
in the brain stem) will make it past the bottleneck to be consciously analyzed for mean-
ing in STM. When a person is thinking actively about information, that information is
said to be conscious and is also in STM. to Learning Objective 4.1.
It is somewhat difficult to use Broadbent’s selective-attention filter to explain the
“cocktail-party effect” that has been long established in studies of perception and atten-
tion (Bronkhorst, 2000; Cherry, 1953; Handel, 1989). If you’ve ever been at a party where
there’s a lot of noise and several conversations going on in the background but you are
still able to notice when someone says your name, you have experienced this effect. In
this kind of a situation, the areas of the brain that are involved in selective attention had
to be working—even though you were not consciously aware of it. Then, when that
important bit of information (your name) “appeared,” those areas somehow filtered the
information into your conscious awareness—in spite of the fact that you were not paying
conscious attention to the other background noise (Hopfinger et al., 2000; Mesgarani &
Chang, 2012; Stuss et al., 2002).
Dr. Anne M. Treisman (Treisman, 2006; Triesman & Gelade, 1980) proposed that
selective attention operates in a two-stage filtering process: In the first stage, incoming
stimuli in sensory memory are filtered on the basis of simple physical characteristics,
similar to Broadbent’s original idea. Instead of moving to STM or being lost, however,
there is only a lessening (attenuation) of the “signal strength” of unselected sensory
stimuli in comparison to the selected stimuli. In the second stage, only the stimuli that
meet a certain threshold of importance are processed. Since the attenuated stimuli are
still present at this second stage, something as subjectively important as one’s own name
may be able to be “plucked” out of the attenuated incoming stimuli. Even when deeply
asleep, when the selective attention filter is not working at its peak level, it still functions:Once these piano strings have been
attached to the tuning pins, the piano can
be tuned. Tuning a piano requires the use
of echoic sensory memory. What other
occupations might find a good echoic
memory to be an asset?selective attention
the ability to focus on only one stimu-
lus from among all sensory input.
short-term memory (STM)
the memory system in which infor-
mation is held for brief periods of time
while being used.