Jill likes candy. Jill has discovered the following trick. If Jill asks for candy during the afternoon then her mother will say "No, it will spoil your supper." However if her mom is on the phone talking to a friend, she will say "OK, you can have a piece. Just go away and don't bother me now." So now Jill waits until her mom is on the phone and then she asks for candy. The mom comes to rely on this method to get Jill to stop bothering her.

If the response is asking for candy when her mom is on the phone, then Skinner would label the effect: