what is biopsychology? chapter 1 the origins of biopsychology nature and nurture

WHAT IS BIOPSYCHOLOGY?CHAPTER 1

The origins of biopsychology

Nature and nurture

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.

PhrenologyFigure 1.6

The Origins of Biopsychology

• Equipotentiality– 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.◊

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.◊

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.◊

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 ChromosomesFigure 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 NurtureGenes 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.

DNAFigure 1.9

Nature and NurtureBecause 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 ClaspingFigure 1.10

Nature and NurtureExample 1: In the previous slide, both Sue and Bill show left-

over-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 NurtureHeritability 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 DisordersFigure 1.13

Nature and NurtureAbout 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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