Disappointment and recovery occur frequently in life; as does irritation regarding ones financial or economic state compared to others. Incentive relativity is the study of this phenomenon, and this book provides a full account of the subject, suitable for behavioral scientists and psychologists. The book shows that animals also respond on the basis of the relative value of rewards - current compared to previous, to the reward available in one situation versus what is available in another context. These relativity effects are stressful in animals but they may also be adaptive, driving animals to seek the best that is available. The book demonstrates that animal research may lead to an understanding of individual differences in discernment and susceptibility to disappointment and to an understanding of both the advantages and disadvantages of dissatisfaction.