With the experience of the first edition, the authors have introduced a few changes of organization in the basic plan. First, the order of the chapters has been changed. In this new organization, chapters dealing with evolutionary theory that were previously dispersed in several sections were brought together into a single part. Second, a section on learning and cognition is moved to an earlier portion of the book, rather than being placed at the end of the book, as in the first edition. The reason for this change relates to the fact that most of the techniques used to understand all aspects of behavior of interest in comparative psychology derive from the study of learning and cognition. Finally, a chapter on feeding behavior included in the first edition will be removed. Key information from this chapter will be transferred to other chapters. Conversely, information on comparative learning and cognition, previously reported in a single chapter, will be divided into two chapters.

These areas have undergone extensive expansion during the past few years and this should be reflected in the new organization. After all, these are the most popular and historically central areas in comparative psychology.