Friday night is dinner night out for sally and harry. when they go to a chinese restaurant, they use chopsticks to eat their noodles, when they go to an italian restaurant they use a fork and a spoon to eat spaghettis. at home, they prefer eating all foods with their hands. although the topography differs, they are functionally equivalent because they all result in getting food in their mouth. these different ways of eating are all part of the same

These different ways of eating are all part of the same "response class".

Response Class refers to a group of responses of changing topography, all of which create a similar impact on the environment.

This implies the responses physically appear to be unique despite the fact that they have a similar impact on the earth. For instance when I wash my clothes I can wash the clothes with hand or I can put the clothes in the washing machine. In the two occurrences when I am done I will have washed the clothes and my clothes will be washed.