Understanding Psychology (10th Ed)

P B S F O X C N N A B C C B S M T V N B C
chunk
A meaningful grouping of 
stimuli that can be stored as a unit in 
short-term memory.
A momentary fl ash of lightning leaves a 
sensory visual memory, a fl eeting but 
exact replica of the stimulus that fades 
away.
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212 Chapter 
7 
Memory
Because the list exceeds seven chunks, it is diffi cult to recall the letters after one 
exposure. But suppose they were presented as follows:
PBS FOX CNN ABC CBS MTV NBC
In this case, even though there are still 21 letters, you’d be able to store them in 
short-term memory since they represent only seven chunks. 
Chunks can vary in size from single letters or numbers to categories that are far 
more complicated. The specifi c nature of what constitutes a chunk varies according 
to one’s past experience. You can see this for yourself by trying an experiment that 
was fi rst carried out as a comparison between expert and inexperienced chess play-
ers and is illustrated in Figure 3 (deGroot, 1978; Oberauer, 2007; Gilchrist, Cowan, & 
Naveh-Benjamin, 2009). 
Although it is possible to remember seven or so relatively complicated sets of 
information entering short-term memory, the information cannot be held there very 
long. Just how brief is short-term memory? If you’ve ever looked up a telephone 
number in a phone directory, repeated the number to yourself, put away the direc-
tory, and then forgotten the number after you’ve tapped the fi rst three numbers into 
your phone, you know that information does not remain in short-term memory very 
long. Most psychologists believe that information in short-term memory is lost after 
15 to 25 seconds—unless it is transferred to long-term memory.
FIGURE 3 
Examine the chessboard on the left for about fi ve seconds. Then cover up the 
board and draw the position of the pieces on the blank chessboard. (You could also use a 
chessboard of your own and place the pieces in the same positions.) Unless you are an 
experienced chess player, you are likely to have great diffi
culty carrying out such a task. Yet 
chess masters—those who win tournaments—do this quite well (deGroot, 1966). They are 
able to reproduce correctly 90% of the pieces on the board. In comparison, inexperienced 
chess players are typically able to reproduce only 40% of the board properly. The chess 
masters do not have superior memories in other respects; they generally test normally on 
other measures of memory. What they can do better than others is see the board in terms 
of chunks or meaningful units and reproduce the position of the chess pieces by using 
those units.
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