Endocrine System

Type of psychology: Biological bases of behavior
Field of study: Endocrine system
Behavior, by definition, includes physiological events which are responses to internal
and external stimuli; the endocrine system, through the action of hormones and in cooperation
with the nervous system, plays a necessary role in bringing about these reactions
in animals and humans.
Key concepts
• adrenal glands
• biopsychology
• endocrine system
• ethology
• hormone
• hypothalamus
• pituitary gland
Curiosity about behavior, both animal and human, is of long standing. The
suspicion that substances in the body contribute to behavior also has a long
history. During the fifth century b.c.e., Hippocrates suggested, in his humoral
theory, that personality was determined by four body fluids: phlegm,
black bile, yellow bile, and blood. The dominance of one or another of the
fluids was associated with a behavior pattern. A proportionate distribution
of the fluids resulted in a balanced personality. This theory has contributed
terms such as phlegmatic, sanguine, bilious, and good- or bad-humored to
describe personality types and states of mind.
Aristotle (384-322 b.c.e.) is reported to have performed castration experiments
on both fowl and men in order to alter behavior. He believed that
something produced by the testes caused typically male behavior. Several
nineteenth century researchers continued the study of the connection between
the testes and male reproductive behavior. In 1849, Arnold Adolphe
Berthold initiated a series of experiments on cockerels. He removed the testes
from six birds and noted their loss of “male” behavior. Testes were transplanted
into the abdomens of half the castrated birds. Successful transplantation
restored the typical male crowing and combativeness.
During the late nineteenth and early twentieth centuries, the sciences became
more organized. Interest in behavior and its causes continued. The
science of ethology, which focuses on animal behavior, came into existence.
In the early 1900’s, John B.Watson founded a branch of psychology that became
known as behavior science. This area of psychology concentrated on
human behavioral studies. Eventually, ethology and behavior science contributed
to biopsychology, a new branch of psychology which incorporates
and applies data from neuroscience, genetics, endocrinology, and physiology
in the quest for biological explanations of behavior. Biopsychology embraces several subdivisions. Physiological psychology focuses on nervous system
and endocrine system research. Psychopharmacology specializes in the
effects of drugs on the nervous system and, ultimately, on behavior. The development
of therapeutic drugs is a goal of this discipline. The neuropsychologist
studies the effects of brain damage on behavior. Psychophysiology
differs from physiological psychology in that the psychophysiologist uses
only human subjects, while the physiological psychologist experiments on
laboratory animals, especially rats.
Early research in physiological psychology focused on the nervous system,
but it soon became evident that the endocrine system also influenced
behavior and that the effects of the two systems were interrelated contributors
to behavior. The endocrine system essentially consists of ductless glands
that produce chemical substances called hormones. The hormones elicit
physiological reactions, either locally or at some distant target site. When
acting at a distance, the hormones travel to the site by way of the circulatory
system.
Hans Selye, a Canadian scientist, proposed a direct connection between
the endocrine system and behavior. In 1946, he described physiological
events that were triggered by stress. This set of bodily changes became
known as the general adaptation syndrome. The syndrome involved the mobilization
of the autonomic nervous system, the adrenal glands, and the anterior
lobe of the pituitary.
As research continued, data on the role of the endocrine system in determining
behavior began to accumulate. Researchers continue to look to the
endocrine system to provide clues about the causes of psychiatric diseases
and the efficacy of hormone therapy in treating the diseases, as well as in altering
behavior patterns.