Answer: discrimination
Explanation: Discrimination in the context of conditioning refers to the the ability of an individual or animal to distinguish between a conditioned stimulus which requires the animal to give a signal when heard and other similar stimulus which when heard does not evoke a signal.
In the scenario above, the dog was conditioned to salivate in response to the sound of a high-pitched tone, which is the conditioned stimulus, Therefore, the failure of the dog to salivate upon hearing the sound of a low-pitched tone shows the dog has distinguished or made a distinction between a low and a high pitched sound.