Learning Targets:

Discuss psychology's abiding interest in how heredity, environment, and evaluation work together to shape behavior.
Identify key research contributions of scientists in the area of heredity and environment.
Predict how traits can be selected for their adaptive value.

AP psychology course and exam description, effective fall 2020. (n.d.). https://apcentral.collegeboard.org/media/pdf/ap-psychology-course-and-exam-description.pdf

Heredity and the Environment

A central debate in psychology is the nature versus nurture debate. What influences us more - our genes and heredity (nature) or our experiences (nurture)? Psychologists who specialize in biological psychology are particularly interested in the relationship between our biological (genes, neurons, etc.) processes and our psychological processes.

Charles Darwin

Charles Darwin, a British naturalist, made significant contributions to the study of heredity and environment in the field of psychology. His theory of evolution by natural selection proposed that species evolve over time through a process of variation and selection, with those best adapted to their environment have a greater chance of surviving and reproducing.

Darwin's theory had profound implications for the study of heredity and environment in psychology. He argued that certain traits and characteristics are inherited through genes, but that environmental factors can also play a role in shaping behavior. This concept is known as nature versus nurture.

Darwin's ideas have had a lasting impact on the study of psychology. They have influenced our understanding of the role of genetics in behavior, as well as the importance of environmental factors such as upbringing, socialization, and culture. Additionally, his emphasis on the importance of adaptation and survival has contributed to our understanding of human motivation and decision-making.

Nature

We are all born with certain genes that predispose us to be a certain way. They determine our height, weight, facial features, and behavior. We are all born with specific genes predisposing us to be a certain way. They determine our height, weight, facial features, and behavior. They are found in every cell nucleus in your body. Remember from the last module that the nucleus is the inner area of a cell that houses its genetic makeup. We are made up of 46 chromosomes, 23 of which we receive from mom and 23 from dad. At conception, each of these 23 chromosomes from your parents comes together to make your genotype or genetic pattern.

Genetically we are all similar. Humans for example share 99.9% of their DNA. That leaves only .1% that makes you different from those around you. However, that .1% is the difference between a Nobel Peace Prize winner and a sociopath.

Evolutionary Psychology

Evolutionary Psychology is the process by which succeeding generations of organisms change in response to changing environments. It helps explain why we have certain traits. Typically, traits that help perpetuate a species are carried on into the next generation, while those that do not fizzle out or become extinct. Evolutionary psychology seeks to explain universal behaviors in terms of how our ancestors faced and dealt with certain problems. For example, in explaining phobias an evolutionary psychologist will always seek to explain how the phobia manifested from past stimulation that was a danger to our ancestors.

To explain our behavior and our minds, evolutionary psychologists rely on the principles of natural selection. Based on this principle, we are more likely to inherit traits that have been crucial to our survival as a species. Charles Darwin has influenced this field of psychology.

Image depicting a cell, which contains a nucleus, which contains a chromosome, which contains DNA

Behavior Genetics

Types of Twins

Identical (Monozygotic) share a placenta and are from one sperm and egg.

Fraternal (Dizygotic) have separate placentas and are from different sperm and eggs. Behavior genetics studies how our environment and genetics shape who we are. To understand how behavioral traits are inherited, behavioral genetic scientists turn to twin and adoption studies. What is gained from twin and adoption studies is a unique opportunity to study what happens when you manipulate home environments.

Types of Twins

Twins are either identical or fraternal. Identical twins develop from a single fertilized egg and are genetically identical while also sharing one placenta or environment while in the womb. There have been about one hundred studies conducted on identical twins separated at birth and the results make a compelling case for nature. These twins who were raised separately have shown many similar traits such as wearing the same type of clothes, having the same mannerisms, marrying people with the same name, and participating in the same hobbies. Fraternal twins develop from separate eggs and have separate placentas. They are no more alike than ordinary brothers and sisters.

Please take a moment to watch this video regarding twin studies. Twin studies have been proven to be a useful tool when examining the nature vs. nurture debate. (Watching the video should take approximately 15 minutes)

Watch the video on Twin Studies and Adoption below.

Video Credit: Twin Studies Video https://www.khanacademy.org/embed_video?v=usnv1_xRCvs (Video is licensed under Creative Commons and is attributed to Khan Academy)

Nurture

Now that we have examined the role of genetics in explaining behavior, let's look at the role of nurture. Nurture describes the influence of external factors on behavior, such as exposure to an environment, peers, culture, and even gender.

Use the activity below to learn more information on how each factor influences behavior.

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