To acquire a better understanding of the structure and development of the human personality, some psychologists study the personalities of animals. Each of the following, if true, contributes to an explanation of the practice mentioned above EXCEPT: ['Field observations of the behavior of young animals often inspire insightful hypotheses about human personality development.', 'It is generally less expensive to perform experiments on animals than it is to perform them on humans.', 'Proper understanding of human personality is thought to provide a model for better understanding the personality of animals.', 'The actions of humans and animals are believed to be motivated by similar instincts, but these instincts are easier to discern in animals.']