Comparative psychology can be defined as the study of the mental processes and behavior of non-human animals. It is particularly associated with the development of behavior, phylogenetic history, and adaptive significance. Comparative psychology addresses numerous issues, while making use of various methods and exploring the behavior of different species, ranging from insects to primates. It is involved in cross species comparison, which include comparisons between animals and humans. One of the prominent areas of research within this field is animal cognition. It is involved in the study of the mental processes which control complex behavior among animals, including concept formation, attention, memory, time estimation, and spatial cognition. This book aims to shed light on the role of comparative psychology in measuring growth and grades of intelligence. It will also provide interesting topics for research, which interested readers can take up. This book, with its detailed analyses and data, will prove immensely beneficial to professionals and students involved in comparative psychology at various levels.