ABSTRACT
Behavior is a characteristic of individuals, al though observations on individuals are usually gathered and averaged so that behaviors ex pressed in common by groups defined by devel opmental stages, genders, or taxonomy can be more generally described. This essay contains a discussion of why individual differences (IDs) have been overlooked and are now studied in comparative psychology. It will also look at how IDs are measured and in what species they have been studied. Some research in IDs with relation to evolution, development, and physi ological influences on behavior will be men tioned, and recent and general references will be mentioned as a starting point for the reader who wishes to know more about the topic.
