Nature vs Nurture

What makes you uniquely you? From the baseball talents of the Alou family to genetic factors in personality, this chapter explores how nature and nurture work together to create human diversity.

How do nature and nurture interact in shaping human behavior?

They work together; each person is unique with their own traits influenced by both genetics (nature) and environment (nurture)

Why are animal studies important for understanding genetic influences on behavior?

They allow controlled breeding experiments that reveal how specific traits, like aggression, can be inherited across generations, which can't be ethically tested in humans.

How did researchers study aggression in wild house mice?

1. Captured genetically diverse wild mice
2. Tested female aggression
3. Selectively bred most aggressive females into high-aggression lines and least aggressive into low-aggression lines
4. Tracked generational behavioral changes

What are monozygotic twins?

Identical twins who share 100% of their genes; they develop from a single fertilized egg that splits early in pregnancy.

What are dizygotic twins?

Fraternal twins who share 50% of their genes, like regular siblings, developing from two separate fertilized eggs.

Why are twin studies considered “nature’s perfect experiment”?

Because identical and fraternal twins share the same environment but differ in genetic similarity, making it easier to separate genetic versus environmental influences.

What do intelligence test correlations in twins reveal?

Identical twins show nearly identical IQ scores, while fraternal twins and siblings show moderate similarity, highlighting genetic influences.

What do adoption studies reveal about genetics and environment?

Adopted children’s IQs tend to resemble their biological parents more than their adoptive parents, indicating strong genetic influence.

In adoption studies, what is the difference between biological and environmental connections?

• Biological: share genes but not environment with birth parents

• Environmental: share environment but not genes with adoptive parents

What do human cells contain that carry genetic information?

23 chromosomes made of DNA, which has a double helix structure.

What is DNA’s role in inheritance?

DNA carries genetic information in sequences of nucleotides.

What are genes?

Specific DNA segments that influence body characteristics; they are the basic units of inheritance.

How many genes are on each chromosome?

Each chromosome contains thousands of genes.

How are chromosomes inherited from parents?

We receive half of our chromosomes from each parent, creating unique genetic combinations that explain similarities and differences.

How do genes shape behavior?

Genes code for the synthesis of specific proteins, which build body structures and organs (e.g., neurons and endocrine glands) and influence behavior and mental processes.

What are examples of physical environmental influences on behavior?

• Exposure to toxic chemicals (lead, mercury, heavy metals)

• Alcohol exposure during pregnancy

• Water and air pollution

What are examples of social environmental influences on behavior?

• Parents, siblings, friends, and neighborhoods

• Culture (shared behaviors, beliefs, values)

• Ethnic group

What is a passive correlation between genes and environment?

When a child inherits genes (e.g., for high intelligence) and the parents also create an environment that matches these traits (e.g., intellectually stimulating home)

What is an active correlation between genes and environment?

When genetically predisposed children behave in ways that actively shape their environment, such as seeking aggressive peers or joining antisocial groups, reinforcing their genetic tendencies

What is the key idea about nature and nurture together?

• Nature provides the basic biological mechanisms and structures

• Nurture shapes behavior and mental processes through experience

• heredity and experience always work together to influence psychological traits.