Observational learning is the ability to learn by witnessing the behavior, emotions and attitudes of other people. This method of learning comes from Albert Bandura's social learning theory and it suggests that there are four conditions necessary for observing and modeling behavior, such as: attention, retention, reproduction, and motivation.
Darrius is trying to play a trick on his housemate. He wants to add more weight to her backpack before she leaves for school, but he doesn't want her to notice it. He should determine the difference threshold so that he doesn't add enough for her to notice the additional weight.