Psychology2016

228 CHAPTER 6

Information is encoded into sensory memory as neural messages in the nervous sys-

tem. As long as those neural messages are traveling through the system, it can be said that

people have a “memory” for that information that can be accessed if needed. For example,

imagine that Elaina is driving down the street, looking at the people and cars on either side

of her vehicle. All of a sudden she thinks, “What? Was that man wearing any pants?” and

she looks back to check. How did she know to look back? Her eyes had already moved

past the possibly pantless person, but some part of her brain must have just processed

what she saw (most likely it was the reticular formation, which notices new and important

information). This is called a “double take” and can only be explained by the presence,

however brief, of a memory for what she saw. to Learning Objective 2.10.

There are two kinds of sensory memory that have been studied extensively. They

are the iconic (visual) and echoic (auditory) sensory systems.

ICONIC SENSORY MEMORY The example of seeing the possibly pantless person is an

example of how the visual sensory system works. The visual sensory system is often

called iconic memory, and it only lasts for a fraction of a second. Icon is the Greek word

for “image.” Iconic memory was studied in several classic experiments by George

Sperling (1960), as shown in the Classic Studies in Psychology feature.

iconic memory
visual sensory memory, lasting only a
fraction of a second.

Classic Studies in Psychology

Sperling’s Iconic Memory Test

George Sperling had found in his early studies that if he presented a grid of letters using a

machine that allowed very fast presentation, his subjects could only remember about four

or five of the letters, no matter how many had been presented.

Sperling became convinced that this method was an inaccurate measure of the

capacity of iconic memory because the human tendency to read from top to bottom

took long enough that the letters on the bottom of the grid may have faded from mem-

ory by the time the person had “read” the letters at the top. He developed a technique

called the partial report method, in which he showed a grid of letters similar to those in

Figure 6. 2 but immediately sounded a high, medium, or low tone just after the grid was

shown. Subjects were told to report the top row of letters if they heard the high tone, the

middle row for the medium tone, or the lowest row for the low tone. As they didn’t hear

the tone until after the grid went away, they couldn’t look at just one row in advance.

Figure 6.2 Iconic Memory Test

Sample grid of letters for Sperling’s test of iconic memory. To determine if the entire grid existed in

iconic memory, Sperling sounded a tone associated with each row after the grid’s presentation.

Participants were able to recall the letters in the row for which they heard the tone. The graph shows

the decrease in the number of letters recalled as the delay in presenting the tone increased.

Rows

of

Letters

Tone Signaling

Which Row

to Report

LHTY

EPNRMedium tone

High tone

SBAX Low tone

10

8

6

4

2

0

Number of

letters r

ecalled

.15.3. 5

Delay in signal (seconds)

Whole Report Level

1.0

Interactive