The behavior changed in this instant is the sons work ethic. It changes because he wants treats like ice cream for good grades. The behavior is being strengthened. The Consequence is being removed. The consequence is not favorable.
The behavior changed is taking aspirin. This behavior changes because if the son takes aspirin to relieve his headache, he will continue to use aspirin. The consequence is being removed and it is not favorable.
The behavior changed here is cursing. This behavior will change because if the son curses, his mother will spank him, so he won't do it. The consequence is being added and it is not favorable.