Hormonal Influences

The work done by researchers in developing contraceptives clarified the
role of hormones in the functioning of the human female reproductive system.
The system operates in a monthly cycle during which ovarian and uterine
changes occur under hormonal control. These hormones do not affect
a woman’s receptivity, which is not limited to fertile periods.

Testosterone derivatives known as anabolic steroids are illegally used by
some athletes in an attempt to increase muscularity, strength, and performance.
While both sexes do experience the desired effects, long-term, highdosage
usage has undesirable consequences. This is particularly true in
women, who begin to exhibit a deepening of the voice, a male body shape,
and increased body and facial hair. Both men and women can become sterile.
Psychotic behaviors and states such as depression and anger have been
recorded.
Developmental biologists indicate that hormones exert their influence as
early as six or seven weeks into embryonic development. At this point, undifferentiated
tissue with the potential of developing into either a female or a
male reproductive system will develop into a male system in the presence of
testosterone and into a female system in its absence. There is some evidence
that the embryonic hormones have an effect on the developing brain, producing
either a male or female brain. Functionally, this may account for the
cyclic activity of female reproductive hormones and the noncyclic activity of
the male. A few anatomical differences between male and female brains
have been observed in both rats and humans. In the hypothalamus of the
brain, there are cell bodies called nuclei. In rats and in humans, these nuclei
are larger in males than in females.
Learning and memory can be experimentally affected by hormones. Experiments
reveal that chemicals which resemble adrenocorticotropic hormone
(ACTH) can extend the memory time of rats. Rats, stimulated by electric
shock and provided with an avoidance possibility such as moving into
another chamber of a cage or climbing a pole in the center of the cage, were
administered ACTH-like molecules. The treated rats were able to remember
the appropriate reaction to the stimulus for a longer period of time than the
untreated rats. In other experiments, rats in a maze were administered
vasopressin, a posterior pituitary hormone, which increased their frequency
in selecting the correct pathway through the maze.
The effect of vasopressin on human memory is not as clearly defined.
There have been positive results with schizophrenic patients and patients
with alcohol-induced amnesia. In these cases, memory has been enhanced
to a limited degree. There is no solid evidence that learning and memory in
humans will be greatly improved by the administration of vasopressin.
Areas such as eating disorders, psychotic behavior, hormone therapy, behavior
modification, and biological clocks and rhythms challenge the physiological
psychologist to further research to test hormonal influences.
Sources for Further Study
Bioscience 33 (October, 1983). The entire issue is devoted to the effects of
hormones on behavior. Includes an article on invertebrates in general,
followed by articles on fish through primates.Written in nonesoteric language.
Brennan, James F. History and Systems of Psychology. 5th ed. Englewood Cliffs,

N.J.: Prentice-Hall, 1997. Readable presentation of the history and development
of psychology. Covers the highlights of the discipline from the
time of ancient Greece. Good background material for those not well
grounded in psychology and interesting reading for those with a historical
leaning.
Donovan, Bernard T. Hormones and Human Behaviour. New York: Cambridge
University Press, 1985. An excellent compilation of the information available
on hormones and behavior up to 1985. Uses technical language, but
one who reads on a high-school level and has had some exposure to science
will find the book informative and interesting. Focuses on the pituitary,
the gonads, and the adrenals, and their effect on human behavior.
Drickamer, Lee C., Stephen H. Vessey, and Elizabeth Jakob. Animal Behavior.
5th ed. New York: McGraw-Hill, 2001. Intended for undergraduate students
who are interested in animal behavior. Of particular interest is
chapter 10, which deals with hormones and behavior. Presents a clear
explanation of the endocrine system and the mechanism of hormone action.
Avoids highly technical language. The effect of hormones on behavior
of invertebrates and vertebrates is well illustrated with many interesting
examples from the animal world.
Highnam, Kenneth Charles, and Leonard Hill. The Comparative Endocrinology
of the Invertebrates. 2d ed. Baltimore: University Park Press, 1977. Various
types of invertebrate endocrine systems are described in this book.
Although the book was published in 1977, it is a valuable source of information,
especially on the insect and crustacean hormones. Technical language
is used but is clearly explained in laypersons’ terms. Drawings and
charts contribute to the understanding of the material.
Pinel, John P. J. Biopsychology. 4th ed. Boston: Allyn & Bacon, 1999. A textbook
intended for use by undergraduate college students. There are two
chapters of particular interest. Chapter 1 defines the position of biopsychology
within the larger field of psychology, delineates the subdivisions
of biopsychology, and describes the type of research carried out in
each area. An account of research involving the human reproductive hormones
and their effects is found in chapter 10. Both chapters are interesting
and well written. The author makes use of good examples, drawings,
and charts.
Rosemary Scheirer
See also: Emotions; Hormones and Behavior; Memory: Animal Research;
Stress: Physiological Responses. 337