Final answer:
The phenomenon of animals responding more to a stimulus slightly different than the conditioned stimulus following discrimination training is known as peak shift.
Step-by-step explanation:
The phenomenon described where animals peck the most for a sound slightly louder than the Sound Discriminant (SD) after receiving discrimination training to peck when hearing a loud buzzer but not a soft buzzer is known as peak shift.
In the context of operant conditioning, stimulus discrimination is crucial as it allows an animal to differentiate between various stimuli and respond accordingly. For instance, a dog might learn to react to a specific tone that signals food availability while ignoring other similar but irrelevant tones.
This ability to differentiate and respond to particular stimuli is a fundamental aspect of both classical and operant conditioning. However, once this discrimination is learned, the peak shift effect occurs when the animal responds most strongly not to the conditioned stimulus itself, but to a stimulus that is even more distinct from the non-conditioned stimulus, hence showing an exaggerated preference for an aspect of the conditioned stimulus.