Which type of discrimination training presents both the SD and SΔ stimulus conditions simultaneously?

Simultaneous discrimination training involves presenting both the discriminative stimulus (SD) and the SΔ (delta stimulus, which signals the absence of reinforcement) at the same time. This allows the learner to directly compare the two stimuli and to learn which one is associated with reinforcement. For instance, if the task is to select the red circle (SD) over a blue square (SΔ) for reinforcement, both stimuli would be shown to the learner at once.

This method is effective because it helps the learner quickly identify the relevant stimulus (the one that leads to reinforcement) while also being aware of the non-reinforcing stimulus. The immediate comparison enhances the learning of the discrimination, making it clearer which behaviors lead to the desired outcomes. Other types of discrimination training may present stimuli sequentially, one after the other, or in other formats that do not allow for the same level of immediate comparison.