Unit 3 continued- Heredity/ Environment/ and Evolution work together to shape behavior.
How traits and behaviors can be selected for their adaptive value.
Brain Continued from last study guide
Key Contributors- People to know
Sir Charles Sherrington- discovered synapse
Paul Broca- found that damage to the a specific part of the left frontal lobe would disrupt speaking
(think Brocan)
Carl Wernicke- found that damage to a specific part of the left frontal lobe disrupts understanding
Charles Darwin- came up with the idea of natural selection that fueled Darwinian thinking- survival of
the fittest;
Roger Sperry- came up with the idea that split brains have “two separate minds”
SPLIT BRAIN Michael Gazzaniga- began research with split brains and tested the divided brain. When an
experimenter flashes the word heart across the visual field, a women with a split brain reports seeing
the portion of the word transmitted to her left hemisphere. However, if asked to indicate with her left
hand what she saw, she points to the portion of the word transmitted to her right hemisphere.
On the back of this handout are practice questions on the split brain with answer keys.
Unit 3C- Nature, Nurture, and Human Diversity
Differences/ Similarities within Human Family
Our differences as humans include our personalities, interests, cultural, and family backgrounds.
Our similarities include our common biological heritage, our shared brain architecture, our ability to
use language, and our social behaviors.
A fundamental question in psychology deals with the extent to which we are shaped by our hereditary,
called our nature, and by external influences, called our nurture. For our classes’ purpose, we will call
this nature via nurture.
Behavior Genetics: Predicting Individual Differences
Researchers who specifically study genetic and environmental influences on behavior are called
behavior geneticists. They view the term environment as a nongenetic influence.
The Master Plans for Development are stored in the chromosomes. In number, each person inherits 46
of these structures, 23 from each parent. Each composed of a coiled chain of the molecule DNA.
If chromosomes are the chapters of heredity, the “words” that make each of us a distinctive human
being are called genes. The complete instructions for making an organism are referred to as the human
genome.
Twin and Adoption Studies
To study the power and limits of genetic influences on behavior, researchers use twin and adoption
studies.
Twins who develop from single a single egg are genetically identical. In terms of extraversion and
neuroticism, identical twins are more alike than fraternal twins. Twins who come from different eggs
are no more genetically alike than siblings and are called fraternal.
Through research on identical twins raised apart, psychologists are able to study the influence of
environment. Studies have shown that personalities of adopted children do not closely resemble those
of their adoptive parents. However, adoption studies show that parenting does matter by showing that
adopted children score higher than their biological parents on intelligence tests. What does this
paragraph tell us? In personality, nature wins (Kagen study on temperament); In intelligence, nurture
wins. Interaction of nature via nurture
Temperament
The term that refers to the inborn personality, especially the child’s emotional excitability is
temperament, which does endure over time.
From first weeks of life, difficult babies are more irritable, intense, and unpredictable while easy babies
are more cheerful, relaxed, and predictable.
Heritability
Heritability- the extent to which variation among individuals can be attributed to differing genes.
Heritable individual differences do not necessary imply heritable group differences.
Genes are self regulating; rather than acting as blueprints that always lead to the same result, they
react to the environmental context. Environments trigger activity in genes and our genetically
influenced traits evoke responses in other people. This may explain why fraternal twins recall greater
variations in their early family life than do identical twins.
Molecular Genetics
Molecular Genetics-subfield of biology that seeks to identify some of the many genes that influence
normal human traits. The goal of researchers is to find some of the genes that influence normal human
traits, such as body weight, sexual orientation, and extraversion. Poses many ethical dilemmas.
Evolutionary Psychology- Understanding Human Nature
Evolutionary Psychologists- Researchers who study natural selection and the adaptive nature of human
behavior. They tend to focus mostly on what makes people so much alike.
According to Darwin’s principle of natural selection, traits that lead to increased reproduction and
survival will be most likely to be passed on to succeeding generations.
Genetic mutations are random errors in genetic replication that are the source of all genetic diversity.
So do genes give a human or animal more free will? Genetic constraints on human behavior are
generally looser than those on animal behavior. The human species ability to learn and therefore to
adapt in responding to different environments contributes to our fitness, defined as our ability to
survive and reproduce. Because of our genetic legacy, we love the tastes of sweets and fats, which we
tend to store, even though famine is unlikely in industrialized societies.
Identifying gender differences in sexuality and mating preferences
Compared to females, males are more likely to engage in casual, impulsive sex, and they are more likely
to initiate sexual activity. This is an example of a gender difference.
The evolutionary explanation of gender differences in attitudes toward sex is based on differences in
the optimal strategy by which women and men pass on their genes. According to this view, males and
females are selected for different patterns of sexuality.
Cross- Cultural research reveals that men judge women as more attractive if they have a youthful
appearance. Whereas women judge men who appear mature, dominant, bold, and affluent as
attractive.
Criticisms of Evolutionary Psychology
Critics of the evolutionary explanation of the gender sexuality differences argue that it often works
backward to propose a hindsight explanation. Also, gender differences in sexuality vary with social
expectations. Gender differences in mate preferences are largest in cultures characterized by gender
inequality. Evolutionary Psychologists counter the criticisms by noting that the sexes, having faced
similar adaptive problems, are more alike than they are different.
Reflections on Nature and Nurture
As brute strength becomes less relevant to power and status, gender roles are converging.
We are product of both nature and nurture, but we are also a system that is open. We know this
because a biopsychosocial approach to development shows that no single factor is all- powerful.
The principle that we should prefer the simplest of competing explanations for a phenomenon called
Occam’s Razor.
BIG IDEAS
Bouchard’s study of twins showed amazing similarities between adult identical twins when they reach
adulthood.
Genetic code exists in entirety in every cell of your body.
Chromosomes- threadlike structures made up of DNA molecules that contain the genes.
DNA- a complex molecule containing the genetic information that makes up the chromosome.
Genes- the biochemical units of heredity that make up the chromosomes, segments of DNA capable of
synthesizing a protein.
Molecular genetics- the subfield of biology that studies the molecular structure and function of genes
Interaction- the interplay that occurs when the effect of one factor (environment) depends on another
factor (heredity)