Final answer:
The heart racing in response to a lion versus a kitten is an example of stimulus discrimination, where an organism learns to react differently to various similar stimuli.
Step-by-step explanation:
The fact that your heart may race when you are confronted by a lion but not when approached by a kitten best illustrates the adaptive value of stimulus discrimination. This is a learning process where an organism learns to respond differently to various stimuli that are similar, exhibiting the conditioned response only to the conditioned stimulus. For example, in Pavlov's experiment, the dogs learned to salivate only at the sound of a specific tone that was associated with food, and not other similar tones. In your scenario, distinguishing between the threat of a lion and the harmlessness of a kitten is an example of stimulus discrimination, as it enables an appropriate reaction to different stimuli.