Understanding Psychology (10th Ed)

participant in his study, Ebbinghaus memorized lists of three-letter nonsense 
syllables—meaningless sets of two consonants with a vowel in between, such as 
FIW and BOZ. By measuring how easy it was to relearn a given list of words after 
varying periods of time had passed since the initial learning, he found that forget-
ting occurred systematically, as shown in Figure 1. As the fi gure indicates, the most 
 Key Concepts 
Why do we forget information? 
What are the major memory 
impairments?
M O D U L E 2 2 
Forgetting: When Memory Fails
FIGURE 1 
In his classic work, Ebbinghaus 
found that the most rapid forgetting 
occurs in the fi rst nine hours after 
exposure to new material. However, the 
rate of forgetting then slows down and 
declines very little even after many days 
have passed (Ebbinghaus, 1885, 1913). 
Check your own memory:
 
What were you 
doing exactly two hours ago? What were 
you doing last Tuesday at 5 p.m.? Which 
information is easier to retrieve?
100
20
P
er
centage of r
etention 
0
Elapsed time (days)
8
2
10
4
6
20
25
15
31
40
60
80
Immediate recall
20 minutes
1 hour
9 hours
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Module 22 
Forgetting: When Memory Fails 
233
rapid forgetting occurs in the fi rst nine hours, particularly in the fi rst hour. After 
nine hours, the rate of forgetting slows and declines little, even after the passage 
of many days. 
Despite his primitive methods, Ebbinghaus’s study had an important infl uence 
on subsequent research, and his basic conclusions have been upheld. There is almost 
always a strong initial decline in memory, followed by a more gradual drop over 
time. Furthermore, relearning of previously mastered material is almost always faster 
than starting from scratch, whether the material is academic information or a motor 
skill such as serving a tennis ball (Wixted & Carpenter, 2007).
Why We Forget
Why do we forget? One reason is that we may not have paid attention to the mate-
rial in the fi rst place—a failure of encoding . For example, if you live in the United 
States, you probably have been exposed to thousands of pennies during your life. 
Despite this experience, you probably don’t have a clear sense of the details of the 
coin. (See this for yourself by looking at Figure 2.) Consequently, the reason for your 
memory failure is that you probably never encoded the information into long-term 
memory initially. Obviously, if information was not placed in memory to start with, 
there is no way the information can be recalled. 
But what about material that has been encoded into memory and that can’t later 
be remembered? Several processes account for memory failures, including decay, 
interference, and cue-dependent forgetting. 
 Decay  is the loss of information through nonuse. This explanation for forgetting 
assumes that memory traces , the physical changes that take place in the brain when 
new material is learned, simply fade away over time (Grann, 2007).
Although there is evidence that decay does occur, this does not seem to be the 
complete explanation for forgetting. Often there is no relationship between how long 
ago a person was exposed to information and how well that information is recalled. 
If decay explained all forgetting, we would expect that the more time that has 
elapsed between the initial learning of information and our attempt to recall it, the 
harder it would be to remember it because there would be more time for the mem-
ory trace to decay. Yet people who take several consecutive tests on the same 
decay
The loss of information in 
memory through its nonuse.
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