In discrimination training, the behavior is not reinforced when the ________ is present.

Here is a tip:
Making a behavior occur only in the presence of its original stimulus and not any other is the first step toward establishing stimulus control.

Explanation
Through stimulus discrimination training, a particular behavior is trained to occur only when the discriminative stimulus is present. This is done by reinforcing the behavior in the presence of the stimulus which was originally associated with the behavior [discriminative stimulus].

The next step in order to ensure stimulus control in the process is to not deliver reinforcement for the behavior when any other stimulus apart from the discriminative stimulus is present. S-delta is the name given to a stimulus in the presence of which the behavior is not strengthened.

Verified Answer
S-delta