The experimental study of the physiological mechanisms of animal behavior, which began in the 1800s, has dual origins. Research on neural mechanisms, now referred to as behavioral neurobiology, neuroethology, or behavioral neuroscience, has its roots in comparative neuroanatomy, comparative physiology, and physiological psychology. Research on hormonal mechanisms, now known as behavioral neuroendocrinology, arose from endocrinology in addition to many other fields. With the realization that the nervous and endocrine systems are functionally connected, there has been increased integration within the field. Connections with several newer branches of science, such as molecular biology, have been established as well.

Introduction

Two types of mechanisms, neural and hormonal, have been prominent in the history of research directed at uncovering the proximate physiological causes of animal behavior. During the first part of this history, the nervous and endocrine systems were envisioned as separate systems and were studied by somewhat different research communities. As a result, research on physiological mechanisms of animal behavior has tended to develop along two somewhat separate and parallel tracks. These dual origins are reflected in the organization of this survey. Beginning in the 20th century, several discoveries led to the realization that the nervous and endocrine systems are physiologically integrated to a highly significant extent, which is of great importance for animal behavior. Nerve cells can synthesize and secrete hormones; the behavioral effects of hormones are mediated by their actions on neurons, and the brain regulates the endocrine axes so that hormone levels related to behavior are responsive to both social and physical environments.

Origins of Behavioral Neurobiology: Sensory, Motor, and Motivational Systems in Comparative Perspective

The history of the study of the neural mechanisms of animal behavior is largely the history of neuroscience in a more general sense. The overarching motivation of the pioneers was often a desire to understand human minds and brains. However, because of the impossibility of doing experimental work with humans, investigations of animals have long played a significant role. The oldest and deepest scientific roots of the field are comparative neuroanatomy and comparative physiology. Then in the 20th century, developments in ethology led to the rise of neuroethology (also called behavioral neurobiology), which emphasized naturally occurring behavior in nondomesticated animals, while developments in psychology produced the subfield of physiological psychology, with its emphasis on learning, memory, and motivation in domesticated laboratory animals.