Heredity and Hormones
The Influences of heredity and hormones on human behavior
The Influence of Heredity and Hormones on Human Behavior
Human behavior has always been fascinating to many people. Scientists have long studied the factors that cause and contribute too many different types of human behaviors.
The Effects Heredity Has On Human Behavior
Many different traits are passed along to people through genetics. Some of these traits include the basics such as eye color, height, and weight. Heredity also affects human behavior as well. Behavior genetics focuses on the extent to which heredity accounts for individual differences in behavior and thinking (Psychology: An Introduction, Twelfth Edition, by Charles G. Morris and Albert A. Maisto. Published by Prentice-Hall, 2005.). Scientists use many different types of studies to examine animal behavior. By doing this, scientists are able to compare their findings to human behaviors. Two of the methods that are used include strain studies and selection studies. Both of these methods can not be used on humans so scientists have found various ways to study human behaviors. The first method is by doing family studies, this helps to learn if genes truly influence traits. The only flaw in this study is that though family members do share the same genes, they also share the same environment. Therefore family
studies alone cannot clearly distinguish the effects of heredity and environment (Plomin,
DeFries, & McClearn, 1990). Scientists also use twin studies to distinguish the effects of
heredity and the environment. This method is helpful because both people share the same
genetic makeup and any differences between them would have to be due to the environment.
Another method used is adoption studies. This type of study is used to determine if the adoptees
behavior is different in a different household. One thing interesting to note is that adoption
studies provide additional evidence for the heritability of intelligence, some forms of mental
illness (Horn, 1983; Scarr & Weinberg, 1983), and in behavior thought to be solely determined
by environmental influences, even smoking (Boomsma, Koopmans, Van Doornen, &
Orlebeke et al., 1994; Heath & Martin, 1993; Lerman et al., 1999).
Though behavior geneticists try to explain differences in human behavior, evolutionary
psychologists explain the commonalities. Evolutionary psychologists believe the key to this is
the process of evolution by natural selection. Natural selection is also known as the Darwin
Theory, a survival of the fittest so to speak. Organisms that are best adapted to their
environments are most likely to survive and reproduce, according to this theory. Evolutionary
psychologists study the origins of behaviors and mental processes, emphasizing the adaptive or
survival value of traits. In the evolutionary psychology world there are many different ideas and
critics within their own group.
The Effects of Hormones on Human Behavior
The endocrine system is made up of endocrine glands produce hormones. Hormones
are chemical substances that are released into the bloodstream. Hormones guide processes such
as metabolism, growth, and sexual development. Hormones can activate behaviors such as
alertness, excitability, sexual behavior, concentration, aggressiveness, and reactions to stress.
The thyroid gland secretes a hormone called thyroxin. Thyroxin can cause different affects on a
person when it is over or under active. Parathyroid’s are four tiny pea shaped organs located
within the thyroid gland that secrete parathormone. This controls and balances the level of
calcium and phosphate in the blood and tissue fluids. The pituitary gland is a complex gland that
plays an important role in body growth. It also produces the largest number of different
References: Psychology: An Introduction, Twelfth Edition, by Charles G. Morris and Albert A. Maisto. Published by Prentice-Hall. Copyright © 2005 by Pearson Education, Inc.
Plomin, DeFries, & McClearn, 1990, Psychology: An Introduction, (accessed 2-19-2010)
Horn, 1983; Scarr & Weinberg, 1983, Psychology: An Introduction, (accessed 2-19-2010)
Boomsma, Koopmans, Van Doornen, & Orlebeke et al., 1994; Heath & Martin, 1993; Lerman et al., 1999, Psychology: An Introduction, (accessed 2-19-2010)
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