Assume you have not had any water for 24 hours. The sign is dark and you wait quietly without pushing the button. The sign comes on, you push the button, and you get a bottle of water. The “water” sign is a discriminative stimulus (SD or SD) for pushing the button. Button pushing results in water only when the sign is on. You could push the button anytime, but you wait for the discriminative stimulus.
An environmental change or event with the following features:
Precedes the response to which it is functionally related
Increases the effectiveness of a particular stimulus change as reinforcement
The type of environmental event
The cause of the environmental event
The type of stimulus that gains reinforcing effectiveness