Dogs conditioned to salivate to stimulation of the thigh also begin to salivate when stimulated on other body parts. this best illustrates

generalization

Explanation:

In generalization conditioning, though the stimuli is different but it has some similarity in its nature which causes similar kind of responses.

Like in this case when dog is condition to salivate when it is stimulated on thighs but since this conditioning transforms into generalized conditioning the dog even salivates when it is stimulated on some other body parts.  

Hence, the correct answer is generalization

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