Every time Harriet cried, her mother would immediately pick her up. Now Harriet is a real crybaby. Based on what is known about operant conditioning, you should conclude that for Harriet, being picked up acted as:

Positive reinforcement

Explanation:

Positive reinforcement is the reinforcement in operant conditioning. Positive reinforcement is something about adding in stimulus so that the subject repeats the behavior. When the behavior repeated it will strengthen the behavior. The best idea to remember about positive reinforcement to think about adding something. By this process, you can remember or you can identify the positive reinforcement in the real situation. Positive reinforcement occurs quite naturally.

Harriet being picked up is the example of positive reinforcement.  

answer; basic psychology;