Answer:
Aversive conditioning.
Explanation:
Aversive conditioning is when something unpleasant action is given to someone for unwanted behavior. In other words, aversive conditioning is the conditioning of behavior by using 'punishments' or 'negative' approach to make the person give up or deflect from that particular behavior.
Henrietta's approach of following her friend's suggestion to use a bitter-tasting cream to make her son stop sucking his thumb is an example of aversion conditioning. The use of the bitter cream allows the son to stop his bad or unwanted behavior of sucking his thumb.