Before katie leaves her dorm room each morning, she looks out the window to check the weather. if the sky is overcast, she puts an umbrella in her backpack. if it is sunny, she leaves her umbrella in the closet. for katie, the sky's appearance is acting as a for carrying an umbrella. select one:

The sky's appearance for Katie, who bases her decisions on its state, acts as what is called the discriminative stimulus.  The discriminative stimulus is the one whose presence will reinforce a a certain and particular response. The existence or absence of this stimulus either increases or decreases the probability of certain response.