Understanding Psychology (10th Ed)

spontaneous recovery
The reemer-
gence of an extinguished conditioned 
response after a period of rest and with 
no further conditioning.
FIGURE 2 
Acquisition, extinction, and 
spontaneous recovery of a classically 
conditioned response. (a) A conditioned 
response (CR) gradually increases in 
strength during training. (b) However, 
if the conditioned stimulus (CS) is 
presented by itself enough times, the 
conditioned response gradually fades, 
and extinction occurs. (c) After a pause 
(d) in which the conditioned stimulus is 
not presented, spontaneous recovery 
can occur. However, extinction typically 
reoccurs soon after.
Time
Strong
Strength of
conditioned response (CR)
Weak
(a)
Training
(b)
CS alone
(c)
Pause
(d)
Spontaneous recovery
Acquisition (conditioned 
stimulus and unconditioned 
stimulus presented together)
Spontaneous recovery of 
conditioned response
Extinction follows 
(conditioned 
stimulus alone)
Extinction (conditioned 
stimulus by itself)
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180 Chapter 
6 
Learning
reemergence of an extinguished conditioned response after a period of time and with 
no further conditioning. 
Spontaneous recovery helps explain why it is so hard to overcome drug addic-
tions. For example, cocaine addicts who are thought to be “cured” can experience an 
irresistible impulse to use the drug again if they are subsequently confronted by a 
stimulus with strong connections to the drug, such as a white powder (DiCano & 
Everitt, 2002; Plowright, Simonds, & Butler, 2006; Rodd et al., 2004).
Generalization 
and Discrimination
Despite differences in color and shape, to most of us a rose is a rose is a rose. The 
pleasure we experience at the beauty, smell, and grace of the fl ower is similar for 
different types of roses. Pavlov noticed a similar phenomenon. His dogs often sali-
vated not only at the ringing of the bell that was used during their original condi-
tioning but at the sound of a buzzer as well. 
Such behavior is the result of stimulus generalization.  Stimulus generalization 
is a process in which, after a stimulus has been conditioned to produce a particular 
response, stimuli that are similar to the original stimulus produce the same response. 
The greater the similarity between two stimuli, the greater the likelihood of stimulus 
generalization. Little Albert, who, as we mentioned earlier, was conditioned to be 
fearful of white rats, grew afraid of other furry white things as well. However, 
according to the principle of stimulus generalization, it is unlikely that he would 
have been afraid of a black dog, because its color would have differentiated it suf-
fi ciently from the original fear-evoking stimulus. 
The conditioned response elicited by the new stimulus is usually not as intense 
as the original conditioned response, although the more similar the new stimulus is 
to the old one, the more similar the new response will be. It is unlikely, then, that 
Little Albert’s fear of the Santa Claus mask was as great as his learned fear of a rat. 
Still, stimulus generalization permits us to know, for example, that we ought to brake 
at all red lights, even if there are minor variations in size, shape, and shade.