Psych Alan always turns the aquarium light on before putting fish food into the tank. After a while, he notices that the fish swim to the top to look for the food as soon as he turns on the light. In this example, the is the unconditioned stimulus.

aquarium light

Explanation:

Unconditioned stimulus -

It refers to the action , smell or any word , that unconditionally initiates the response , is referred to as the unconditioned stimulus .

For example , the smell of food , make the person hungry , here the smell of food acts as an unconditioned stimulus .

Similarly , the lights of the aquarium acts to trigger the fishes about the food and all comes to the top , in order to catch food .

Hence , the correct answer is aquarium light .