Download What is Biopsychology? Chapter 1

The origins of biopsychology
Nature and nurture
WHAT IS BIOPSYCHOLOGY?
CHAPTER 1
The Origins of Biopsychology
• What is neuroscience?
– The study of the nervous system and behavior
• What is biopsychology?
– The study of the body/behavior relationships by psychologists
– Sometimes called psychobiology or physiological psychology
• What kinds of questions do neuroscientists study?
– How do we recognize the face of a friend?
– What role does the brain play in depression or anxiety?
– And, the hardest question of all:
How does the brain’s activity result in consciousness?
The Origins of Biopsychology
• The mind-body or mind-brain problem
– Does one control the other?
– Are they one and the same?
• Monism
– Mind and body are composed of the same substance.
– Most neuroscientists believe in materialistic (physical) monism.
• Dualism
– For most, the body is material but the mind is nonphysical.
– Most dualists believe the mind influences behavior through the brain.
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The Origins of Biopsychology
• Descartes used a hydraulic model to explain the brain’s activity.
• Animal spirits were pumped through the brain by the pineal gland, the “seat
of the soul.”
• The model was not supported by empiricism, which employs observation and
experimentation.
• Descartes’ contribution was advancing a physical explanation of behavior.
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The Origins of Biopsychology
• The Electrical Brain
– Galvani (late 1700s) showed that electrical stimulation of muscle made frog’s leg
move.
– Fritsch & Hitzig (1870) produced movement by electrically stimulating dog’s
brain.
– Helmholtz measured speed of conduction in nerve.
– These researchers helped establish that:
• Neural conduction is biological in nature.
• Neural functioning is open to scientific study.
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The Origins of Biopsychology
• Localization is the idea that specific areas of the
brain carry out specific functions
– Phineas Gage’s case located important behavioral controls in
the frontal lobes.
– Broca’s study of a brain-damaged patient with inability to
speak located Broca’s area in left hemisphere
• Phrenology
– Gall’s extreme theory of localization
• Located 35 different “faculties” of emotion and intellect
• Their strength was assessed from the size of bumps on a
person’s skull.
Phrenology
Figure 1.6
The Origins of Biopsychology
• Equipotentiality
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Karl Lashley proposed this extreme view.
Equipotentiality is the opposite of localization.
The brain functions as an undifferentiated whole.
The extent of damage, not the location, determines how much function
is lost.
• What we know today
– Functions are both distributed and localized.
– Behavior results from the interaction of many widespread areas of the
brain.
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The Origins of Biopsychology
 The brain-mind problem is still being debated.
 The Discovery Institute promotes intelligent design and a
nonmaterial view.
 The institute funds non-material neuroscientists.
 Nonmaterialists interpret the finding that psychotherapy changes brain
activity as evidence of mind changing the brain.
 The materialist neuroscientists’ response:
 This research can also be interpreted as the brain changing the brain.
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Nature and Nurture
• How important is nature or heredity in shaping
behavior?
• How important are environmental influences (nurture)
in shaping behavior?
• Arguments are often based on emotion, not evidence.
• An increasing number of behaviors are turning out to
have some degree of hereditary influence (nature).
• Therefore, it is necessary to understand what nature
and heredity are.
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Nature and Nurture
• The gene is the biological unit that directs cellular
processes and transmits inherited characteristics.
– Most located on chromosomes within the cell’s nucleus
– Some are found within mitochondria
• Chromosomes
– Body cells have 46 chromosomes arranged in 23 pairs.
– Sex cells (sperm and ova) contain 23 chromosomes.
– Sex chromosomes are designated either X or Y.
• XX produces female
• XY produces male
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Human Chromosomes
Figure 1.8
Nature and Nurture
• The zygote is a fertilized egg.
– Receives 23 chromosomes from the male parent’s sperm.
– Receives 23 chromosomes from the female parent’s ovum.
– Hence, the zygote contains 46 chromosomes.
• Embryo
– First 8 weeks of life
• Fetus
– From 8 weeks to birth
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Nature and Nurture
 Genes are made of DNA.
 DNA is deoxyribonucleic acid.
 DNA is a double-stranded chain of chemical molecules that
looks like a twisted ladder.
 DNA is often referred to as the “double helix”.
 Nucleotides
 Two nucleotides form each rung of the ladder.
 Adenine and Thymine, and Guanine and Cytosine
(A, T, G, C)
 Order of these nucleotides determines genetic code.
 Genes provide the directions for making proteins
for use in constructing the body and to act as
enzymes.
DNA
Figure 1.9
Nature and Nurture
 Because chromosomes are paired, most genes are
as well.
 Sometimes a single pair of genes determines a characteristic
(blood type) or disease (Huntington’s disease).
 Different versions of a gene are called alleles.
 A dominant gene will produce its effect regardless
of which gene it is paired with.
 A recessive gene will have an effect when paired
with the same recessive gene on the other
chromosome.
 X-linked traits are produced by a gene on the X
chromosome that is not paired with a gene on Y.
Nature and Nurture
• Dominance and recessiveness are illustrated in
hand clasping preference.
– The allele for left thumb over right thumb preference is
dominant, whereas the allele for right-over-left is recessive.
– If Sue is homozygous for the dominant allele she will show left
preference.
– If Bill is heterozygous for hand clasping, he will also show left
preference.
– Sue and Bill have the same phenotype, but different genotypes.
– What combination of alleles would be required for someone to
show right preference?
Hand Clasping
Figure 1.10
Nature and Nurture
 Example 1: In the previous slide, both Sue and Bill show leftover-right preference, but Sue is homozygous and Bill is
heterozygous for the trait.
 What preference will their children show?
 All will likely show left-over-right preference.
 Why?
 Example 2: Kelly and Jason are both heterozygous for the
trait of hand clasping preference.
 What preference will their children show?
 Three out of four (75%) are likely to show left-over-right
preference.
 Why will one out of four (25%) show right-over-left preference?
Nature and Nurture
• Some traits are determined by a single pair of
genes.
– This is rare.
• Most characteristics are determined by several
genes and hence are referred to as polygenic traits.
• Examples of polygenic characteristics:
– Height
– Intelligence
– Psychological disorders
• Genes do not provide a script for behavior.
• Genes control the production of proteins.
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Nature and Nurture
• Human Genome Project
– Goal was to map the location of all the genes of the human
chromosomes and to determine their codes.
– This was an international effort.
– In 2000—after just 10 years—“rough drafts” of the human
genome were available.
– Three years later the project was 99% complete.
• What has the map revealed?
– We have only 20,000 to 25,000 functioning genes.
– About 97% of our DNA does not encode for proteins and is
referred to as “junk” DNA, but it must play some role.
– Noncoding DNA most likely controls gene expression.
Nature and Nurture
• How many different genetic combinations can be
passed on from two parents to their offspring?
– 60-70 trillion!
– Hence, sexual reproduction increases individuality as
well as adaptability.
• This variability is an essential component of
Darwin’s principle of natural selection.
– Individuals whose genes provide them with a greater ability to
adapt are more likely to survive and transmit their genes to
more offspring.
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Nature and Nurture
 Heritability is the percentage of the variation in a
characteristic that can be attributed to genetic
factors.
 Heritability can be calculated by comparing
concordance rate for types of twins
 Identical twins share 100% of their genes.
 Fraternal twins share about 50% of their genes.
 Some estimated heritability rates are
 Intelligence: 50%
 Schizophrenia: 60-90%
 Height: 90%
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Twin Studies: Behavioral vs. Medical Disorders
Figure 1.13
Nature and Nurture
 About half of the variability in behavioral characteristics is due to
heredity; the other half is due to environmental influences.
 The vulnerability model points out that the influence of genes is
only partial.
 Genes contribute a predisposition for the disorder.
 The combination of genes and environmental factors determines whether the
individual develops the disorder.
 Most scientists reject the nature-versus-nurture concept; they
conclude that heredity and environment interact to influence
behavior.
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