Unit 3C notes, Genetics, Evolutionary Psych and Behavior
(Updated for 2011; goes with Ch. 3 in 2007 book)
I Behavior genetics page 94
What are genes and how do behavior geneticists explain our individual
differences?
A. Chromosomes contain genes; 23 in egg or sperm= 46 in a human cell
B. DNA a molecule containing genetic information that makes up chromosomes
C. Genes made of DNA; units of heredity; segment of DNA capable of synthesizing a
protein
Chimp-Human similarity is 99.4%.
D. Human genome project
Attempts to discover the common sequence of all 3 billion letters in the human DNA
Behavior genetics: Studies the effects of genetics and the environment on human
behavior
Interlock your fingers. Is the right or left thumb on top? Genetics determines this.
Short forefingers in females: recessive; in males, dominant.
Twin and adoption studies page 96
A. Identical twins develop from the same fertilized egg, creating two genetically
identical persons
B. Fraternal twins develop from separate eggs, genetically no closer than brothers
and sisters
C. Separated twins: the Jim twins. 97-98 First pair studied by Bouchard at U. of
Minn.
D. Twin studies
1. Identical twins are more similar than fraternal in abilities, personality traits, risk
of divorce and interests
Critics of Bouchard: anecdotal studies are not data.
2.Identicals separated at birth show remarkable similarities
E. Biological v. Adoption relative studies 99
People who grow up together do not have personality resemblance
(environment has little impact)
1.Adoptees have more similarities to their biological parents
a. Adoptive parents do influence attitudes and values
3.Genes influence such things as Alzheimer’s, outgoingness, and emotional instability
(neuroticism)
Judith Harris: The Nurture Assumption.
E. Temperament: characteristic emotional reactivity and sensitivity. (See
also page 428 for temperament and attachment discussion.)
1. Some babies are born relaxed/cheerful, while others born tense/irritable
2. Identical twins will have more similar temperaments than non-identical
What is heritability and how does it relate to individuals and groups?
F. Heritability indicates what percent of traits are due to genetics
If heritability of intelligence (or height, eye color, etc.) is 40%, that means that 40%
of people will have inherited intelligence; 40% of the observed difference can be
attributed to genes
The father of behaviorism, John Watson (see pp. 6-7, 223-7) believed environment
was the single greatest determinant of behavior and thinking.
Group differences are not necessarily explained by genetics. Social environment
matters.
Nature and Nurture, page 101
It’s not nature v. nurture; it’s nature via nurture
Genes predispose people toward depression and other psychological disorders.
Genes are self-regulating: environmental circumstances can express some genes that
are not expressed in other environments.
Breast feeding can increase intelligence if a certain gene is present.
G. Gene-environment interaction, 101
We are products of gene predispositions and the environment
Interactions are the effect of one factor depending on another factor
People who are judged as more attractive are more likely to get a job or a promotion
illustrating the influence of genes on the environment
H. Molecular Genetics 102
What is the promise of molecular genetics research?
Studies molecular structure and the function of genes
“bottom up” research: what specific genes influence a behavior?
The micro level of understanding (similar to Unit 5 and sensation/perception)
What mechanisms control gene expression?
II.
Evolutionary Psychology page 103
How do evolutionary psychologists use natural selection to explain behavior tendencies?
Studies the effects of evolution on the behavior of humans
Ordinary offspring compete for survival
Biological and behavioral variations increase an organism’s reproductive and survival
chances in their particular environment
Offspring that survive are more likely to have children and pass on their genes
This can lead to a change in population characteristics
A. Natural Selection and Adaptation
If you engage in behaviors that enable you to survive and reproduce, those
behaviors have been naturally selected for
They have been genetically predisposed
An adaptation example is like breeding foxes to behave like dogs
B. Mutations 104
Random errors in gene replication that lead to change in nucleotide sequences
The source of all genetic diversity
Evolutionary success helps explain similarities
Shared human traits were shaped by natural selection
Behavior tendencies, thinking and learning that contributed to success helped to shape
the human genome
Outdated tendency: our eating habits are a better fit for prehistoric times
Evolutionary Psych Today, 105
Not about how one species evolved into another.
About how genetics and environment interact leading to a change in genetics that fits the
environment.
Traits that lead to survival are more likely to be passed on.
An Evolutionary Explanation of Human Sexuality
How might an evolutionary psychology explain gender differences in sexuality and
mating preferences?
C. Gender differences and sexuality 105
1 women more likely to disapprove of/engage in casual sex
2. men more likely to initiate sex
3. men more likely to perceive warm responses as sexual advances
4. men prefer features suggesting youth and health
5. women prefer mates with resources and social status
D. Natural selection and mating preferences, 106
Youthful appearance is more attractive for men across cultures
Women attracted to mature, dominant, bold, affluent men
F. compared with eggs, sperm are inexpensive
G. women must care for an infant while the man can spread his genes around
The evolutionary principle: nature selects behaviors that increase the
likelihood of passing on one’s genes.
E. Criticisms of the evolutionary perspective 107
What are the key criticisms of evolutionary psychology?
H. they make too many hindsight explanations
They don’t account for cultural facts that shape our behavior: what is attractive now
wasn’t in the 1950s.
Social and cultural factors shape gender differences in mate selection
Reflections on nature and nurture, page 108
1. we are the product of nature and nurture
The bio-psycho-social model see page 109, figure 3C.4
2.Roger Sperry views the brain and mind as a holistic system: the brain creates
and controls the emergent mind, which in turn influences the brain; see 110, fig.
3C.5
KEY TERMS, PAGE 111