Chapter 1
The Biological Approach To
Psychology
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The Biological Approach to Behavior
(cont’d.)
• Biological psychology: the study of the
physiological, evolutionary and
developmental mechanisms of behavior and
experience
• A strong emphasis is placed upon brain
functioning
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The Biological Approach to Behavior
(cont’d.)
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
The Biological Approach to Behavior
(cont’d.)
• Brain functioning can be explained at a more
microscopic level in terms of neuron and glia
activity
• Neurons and glia somehow produce an
enormous wealth of behavior and experience
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The Biological Approach to Behavior
(cont’d.)
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Biological Explanations of Behavior
• Biological explanations of behavior:
– Physiological: relates a behavior to the activity
of the brain and other organs
– Ontogenetic: describes the development of a
structure or behavior including the influences
of genes, nutrition, and experiences
– Evolutionary: reconstructs evolutionary history
of a behavior or structure
– Functional: describes why a structure or
behavior evolved as it did
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Biological Explanations of Behavior
(cont’d.)
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Genetics and Behavior
• Both genes and environment interact to shape
human behavior
• The fundamental issue is how much a role each
factor plays in shaping human behaviors
• Examples: psychological disorders, weight gain,
personality, sexual orientation
• Researchers examined facial expressions of
people who were born blind and therefore could
not have learned to imitate facial expressions
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
Mendelian Genetics
• Gregor Mendel demonstrated that inheritance
occurs through genes
• Genes are aligned along chromosomes
(strands of genes) and come in pairs
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Mendelian Genetics (cont’d.)
• A gene is a portion of a chromosome and is
composed of deoxyribonucleic acid (DNA)
• DNA serves as a model for the synthesis of
ribonucleic acid (RNA)
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Mendelian Genetics (cont’d.)
• RNA is a single strand chemical that can
serve as a template/ model for the synthesis
of proteins
• Proteins determine the development of the
body by:
• Forming part of the structure of the body
• Serving as enzymes, biological catalysts
that regulate chemical reactions in the
body
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Mendelian Genetics (cont’d.)
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Mendelian Genetics (cont’d.)
• Homozygous, for, a gene means that a
person has an identical pair of genes on the
two chromosomes
• Heterozygous, for a gene, means that a
person has an unmatched pair of genes on
the two chromosomes
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Mendelian Genetics (cont’d.)
• Genes are either dominant, recessive, or
intermediate
– Examples: eye color, ability to taste PTC
• A dominant gene shows a strong effect in
either the homozygous or heterozygous
condition
• A recessive gene shows its effect only in the
homozygous condition
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
Mendelian Genetics (cont’d.)
• Examples such as PTC and hair color can be
misleading
– Implies that a single gene combination
completely controls a characteristic, but
this is not true
• Some genes are only expressed partly: in
some cells and not others or only under
certain circumstances
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Mendelian Genetics (cont’d.)
• Types of genes include:
– Autosomal genes: all other genes except
for sex- linked genes
– Sex-linked genes: genes located on the
sex chromosomes
• In mammals, the sex chromosomes are
designated X & Y
– Females have two X chromosomes (XX)
– Males have an X and a Y chromosome
(XY)
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Mendelian Genetics (cont’d.)
• During reproduction:
– Females contribute an X chromosome
– Males contribute either an X or a Y
chromosome that determines the sex of
the child
• If an X chromosome is contributed by the
male, the offspring is female
• If a Y chromosome is contributed by the male,
the offspring will be male
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Mendelian Genetics (cont’d.)
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
Mendelian Genetics (cont’d.)
• The human Y chromosome has genes for 27
proteins
• The human X chromosome has genes for
approximately 1500 proteins
• Thus, sex-linked genes usually refer to Xlinked genes: e.g., red-green color deficiency)
• Sex-limited genes are genes that are present
in both sexes but mainly have an effect on
one sex (chest hair, breast size, etc.)
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Mendelian Genetics (cont’d.)
• Genes change in several ways:
– Mutation: a heritable change in a DNA
molecule
– Microduplication/microdeletion: part of a
chromosome that might appear once might
appear twice or not at all
– Example: some researchers believe
schizophrenia might be a result of
microduplications and microdeletions of
brain-relevant genes
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Mendelian Genetics (cont’d.)
• Epigenetics: a field that is concerned with
changes in gene expression without the
modification of the DNA sequence
• Some genes are active only at a certain point
in one’s life, a certain time of day, etc.
• Changes in gene expression are central to
learning and memory
• Epigenetic differences are a likely explanation
for differences between monozygotic
“identical” twins
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Mendelian Genetics (cont’d.)
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
Mendelian Genetics (cont’d.)
• What you do at any moment not only affects
you now, but produces epigenetic effects that
alter gene expressions for a longer period of
time
• Experiences like maternal deprivation,
cocaine exposure, new learning, alter the
activity of genes
• Mice given some dietary supplements have
epigenetic changes affecting expression of
some genes, which affects their fur color,
weight, and propensity to develop cancer
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Heredity and Environment
• Almost all behaviors have both a genetic
component and an environmental component
• Researchers study monozygotic (“from one
egg”) and fraternal/dizygotic (“from two eggs”)
twins to infer contributions of heredity and
environment
• Researchers also study adopted children and
their resemblance to their biological parents
to infer hereditary influences
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Heredity and Environment (cont’d.)
• Heritability refers to how much characteristics
depend on genetic differences
• Researchers have found evidence for
heritability in almost every behavior (e.g.
speed of second language learning) tested
• Heritability of a certain trait is specific to a
given population
• Strong environmental influences may cause
genetic influences to have less of an effect
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Heredity and Environment (cont’d.)
• Traits with a strong hereditary influence can
by modified by environmental intervention
– e.g., PKU: a genetic inability to metabolize
the amino acid phenylketonuria
– If PKU is not treated, phenylalanine
accumulates to toxic levels, impairing brain
development
• Environmental interventions (strict lowphenylalanine diet) can modify PKU
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PKU
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Heredity and Environment (cont’d.)
• Genes do not directly produce behaviors
• Genes produce proteins that increase the
probability that a behavior will develop under
certain circumstances
• Genes can also have an indirect affect
– Genes can alter your environment by
producing behaviors or traits that alter how
people in your environment react to you
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Heredity and Environment (cont’d.)
• Suppose your genes make you unusually
attractive. As a result, strangers smile at you
and many people want to get to know you.
• Their reactions to your appearance may
change your personality, and if so, the genes
altered your behavior by altering your
environment.
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The Evolution of Behavior
• Evolution refers to a change in the frequency
of various genes in a population over
generations
• Regardless if helpful or harmful to the species
• Evolution attempts to answer two questions:
– How did some species evolve?
– How do species evolve?
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The Evolution of Behavior (cont’d.)
• How species did evolve involves the tentative
construction of “evolutionary trees”
• How species do evolve rests upon some
assumptions:
– Offspring generally resemble their parents
for genetic reasons
– Mutations, recombination, and
microduplications of genes introduce new
heritable variations
– Certain individuals successfully reproduce
more than others do
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
The Evolution of Behavior (cont’d.)
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
The Evolution of Behavior
• Artificial selection refers to choosing
individuals with desired traits and making
them parents of the next generation
• Breeders have produced exceptional
racehorses, hundreds of kinds of dogs,
chickens that lay huge numbers of eggs.
• According to Darwin, nature also selects, and
successful individuals’ genes will be prevalent
in later generations
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Artificial Selection
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Artificial Selection
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The Evolution of Behavior (cont’d.)
• Common misconceptions about evolution
include the following:
– Lamarckian evolution: “The use or disuse
of some structure or behavior causes an
increase or decrease in that behavior.”
– “Humans have stopped evolving.”
– “Evolution means improvement.”
– “Evolution acts to benefit the individual or
the species.”
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Lamarckian evolution
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The Evolution of Behavior (cont’d.)
• Evolutionary psychology focuses upon
functional and evolutionary explanations of
how behaviors evolved
– Assumes that behaviors characteristic of a
species have arisen through natural
selection and provide a survival advantage
• Examples: differences in peripheral/color
vision, sleep mechanisms in the brain,
eating habits, temperature regulation
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
The Evolution of Behavior (cont’d.)
• Some animal species have better color vision
than others, and some have better peripheral
vision. Presumably, species evolve the kind
of vision they need for their way of life
• Bears eat all the food they can find, because
bears’ main foods—fruits and nuts—are
available in large quantities for only short
times.
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The Evolution of Behavior (cont’d.)
• Social dominance: The males of many
species establish a hierarchy of social
dominance through combative encounters.
• In some species dominant males copulate
more than nondominant males and thus are
more effective in passing on their
characteristics to future generations.
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
The Evolution of Behavior (cont’d.)
• Men in most cultures value youth and
attractiveness (both indicators of fertility)
• Women value power and earning capacity
more than men do.
• Physical attractiveness best predicts which
women will bond with men of high
occupational status.
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The Evolution of Behavior (cont’d.)
• Some behaviors are more debatable regarding
the influence of natural selection
• Examples include:
– Life span length
• Altruistic behavior: a behavior that benefits
someone other than the actor (e.g. some people
donate a kidney to save life of someone they
didn’t even know)
• Altruism is hard to find outside of humans
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The Evolution of Behavior
• A gene only spreads if individuals with it
reproduce more than individuals without it
• Group selection is a controversial hypothesis
that states that altruistic groups survive better
than less cooperative ones
• Kin selection is the favored explanation:
selection for a gene that benefit’s the
individual’s relatives
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The Evolution of Behavior (cont’d.)
• Reciprocal altruism is the idea that individuals
help those that will return the favor
• Building a reputation for helpfulness only
works if others are willing to cooperate with
you
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The Use of Animals in Research
• Animal research is an important source of
information for biological psychology but
remains a highly controversial topic
• Animal research varies on the amount of
stress and/ or pain that is caused to the
animal itself
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Reasons for Animal Research
• Reasons for studying animals include:
– The underlying mechanisms of behavior
are similar across species and often easier
to study in nonhuman species
– We are interested in animals for their own
sake
– What we learn about animals sheds light
on human evolution
– Some experiments cannot use humans
because of legal or ethical reasons
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May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.
The Ethical Debate
• Opposition to animal research varies:
– “Minimalists” favor firm regulation on
research and place consideration upon the
type of animal used and the amount of
stress induced
– “Abolitionists” maintain that all animals
have the same rights as humans and any
use of animals is unethical
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The Ethical Debate (cont’d.)
• Justification for research considers the
amount of benefit gained compared to the
amount of distress caused to the animal
– No clear dividing line exists
• Colleges and research institutions in the
United States are required to have an
Institutional Animal Care and Use Committee
– Oversees and determine acceptable
procedures
© 2013 Cengage Learning. All Rights Reserved. This edition is intended for use outside of the U.S. only, with content that may be different from the U.S. Edition.
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© 2013 Cengage Learning. All Rights Reserved. This edition is intended for use outside of the U.S. only, with content that may be different from the U.S. Edition.
May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.