Chapter 3: The Biological Bases of Behavior

1. Chapter 3: The Biological Bases of Behavior

2. Communication in the Nervous System Hardware: Glia � structural support and insulation Neurons � communication Soma � cell body Dendrites � receive Axon � transmit away Behavior depends on rapid information travel and processing�the nervous system is the body�s communication network, handling information just as the circulatory system handles blood. The basic components of the nervous system are living cells called neurons and glia. Glia are cells that provide structure and insulation for neurons�neural �glue.� Neurons are cells that receive, integrate, and transmit information�permitting communication in the nervous system. A �typical� neuron consists of a soma, or cell body; dendrites, which are feeler-like structures specialized to receive information; and an axon, which is a long, thin fiber that transmits signals away from the soma to other neurons, or to muscles or glands�the basic flow of information is as follows�the dendrite receives a signal, the signal passes through the soma and down the axon to the dendrites of another neuron. Behavior depends on rapid information travel and processing�the nervous system is the body�s communication network, handling information just as the circulatory system handles blood. The basic components of the nervous system are living cells called neurons and glia. Glia are cells that provide structure and insulation for neurons�neural �glue.� Neurons are cells that receive, integrate, and transmit information�permitting communication in the nervous system. A �typical� neuron consists of a soma, or cell body; dendrites, which are feeler-like structures specialized to receive information; and an axon, which is a long, thin fiber that transmits signals away from the soma to other neurons, or to muscles or glands�the basic flow of information is as follows�the dendrite receives a signal, the signal passes through the soma and down the axon to the dendrites of another neuron.

5. Neural Communication:Insulation and Information Transfer Myelin sheath � speeds up transmission Terminal Button � end of axon; secretes neurotransmitters Neurotransmitters � chemical messengers Synapse � point at which neurons interconnect For efficient neural transmission to take place, many axons are covered with an insulating material called myelin. Myelin sheaths speed up transmission of signals that move along axons. Multiple sclerosis is a myelin degeneration disease, causing loss of muscle control, etc. due to loss of transmission efficiency in the nervous system when the myelin sheaths deteriorate. At the end of an axon, the terminal buttons are small knobs that secrete chemical messengers called neurotransmitters. When the signal gets to the end of the axon, it causes these chemical messengers to be released into the synapse�the junction of two neurons. The chemicals flow across the synapse and stimulate the next cell. For efficient neural transmission to take place, many axons are covered with an insulating material called myelin. Myelin sheaths speed up transmission of signals that move along axons. Multiple sclerosis is a myelin degeneration disease, causing loss of muscle control, etc. due to loss of transmission efficiency in the nervous system when the myelin sheaths deteriorate. At the end of an axon, the terminal buttons are small knobs that secrete chemical messengers called neurotransmitters. When the signal gets to the end of the axon, it causes these chemical messengers to be released into the synapse�the junction of two neurons. The chemicals flow across the synapse and stimulate the next cell.

6. The Neural Impulse:Electrochemical Beginnings Hodgkin & Huxley (1952) - giant squid Fluids inside and outside neuron Electrically charged particles (ions) Neuron at rest � negative charge on inside compared to outside -70 millivolts � resting potential Alan Hodgkin and Andrew Huxley in the 1950�s discovered the mechanics of neural transmission by studying giant squid�which have axons that are about 100 times larger than human axons. Found that fluids inside and outside the neuron contain electrically charged particles, or ions. Also found that when a neuron is �at rest� the inside has more negative ions than the outside. The stable negative charge of a neuron when it is inactive is its resting potential. Alan Hodgkin and Andrew Huxley in the 1950�s discovered the mechanics of neural transmission by studying giant squid�which have axons that are about 100 times larger than human axons. Found that fluids inside and outside the neuron contain electrically charged particles, or ions. Also found that when a neuron is �at rest� the inside has more negative ions than the outside. The stable negative charge of a neuron when it is inactive is its resting potential.

7. sodium�potassium pump potassium ions K+ inside the neuron is roughly 20-fold larger than the outside concentration, whereas the sodium concentration outside is roughly ninefold larger than inside other ions have different concentrations inside and outside the neuron, such as calcium, chloride and magnesium.

8. The Neural Impulse: The Action Potential Stimulation causes cell membrane to open briefly Positively charged sodium ions flow in Shift in electrical charge travels along neuron The Action Potential All � or � none law When a neuron is stimulated, channels in the cell membrane open briefly, allowing the positive ions outside the cell to flow into the electronegative inside�this shift in the electrical charge travels along the axon and is referred to as an action potential. Either an action potential occurs, or it doesn�t. Once an action potential is initiated, it goes full force. When a neuron is stimulated, channels in the cell membrane open briefly, allowing the positive ions outside the cell to flow into the electronegative inside�this shift in the electrical charge travels along the axon and is referred to as an action potential. Either an action potential occurs, or it doesn�t. Once an action potential is initiated, it goes full force.

10. The Synapse: Chemicals as Signal Couriers Synaptic cleft Presynaptic neuron Synaptic vesicles Neurotransmitters Postsynaptic neuron Receptor sites Neurons don�t actually touch at a synapse, instead they are separated by a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron - the synaptic cleft. Electrical signals can�t jump this gap. Instead, the neuron that is sending the message across the gap (the presynaptic neuron) releases neurotransmitters into the synaptic cleft. This occurs when the action potential gets to the terminal button and causes the synaptic vesicles (storage sacs for the neurotransmitter) to fuse with the membrane at the end of the axon and spill its contents into the synaptic cleft. The neurotransmitters diffuse across the space where they find open receptor sites on the postsynaptic neuron. These sites recognize and respond to some neurotransmitters, but not to others. Neurons don�t actually touch at a synapse, instead they are separated by a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron - the synaptic cleft. Electrical signals can�t jump this gap. Instead, the neuron that is sending the message across the gap (the presynaptic neuron) releases neurotransmitters into the synaptic cleft. This occurs when the action potential gets to the terminal button and causes the synaptic vesicles (storage sacs for the neurotransmitter) to fuse with the membrane at the end of the axon and spill its contents into the synaptic cleft. The neurotransmitters diffuse across the space where they find open receptor sites on the postsynaptic neuron. These sites recognize and respond to some neurotransmitters, but not to others.

13. When a Neurotransmitter Binds:The Postsynaptic Potential Voltage change at receptor site � postsynaptic potential (PSP) Not all-or-none Changes the probability of the postsynaptic neuron firing Positive voltage shift � excitatory PSP Negative voltage shift � inhibitory PSP When a neurotransmitter from the presynaptic neuron crosses the synapse, finds an appropriate receptor site on the postsynaptic neuron, and binds, a voltage change occurs. This voltage change in the postsynaptic neuron is not an all-or-none, the neuron will fire or it won�t, kind of thing. Instead, it changes the probability or potential that the postsynaptic neuron will fire. This is, therefore, called a postsynaptic potential. The postsynaptic potential can be excitatory or inhibitory. An excitatory potential makes the neuron more likely to fire�decreases the negativity of the inside of the neuron with respect to the outside. An inhibitory postsynaptic potential increases the negativity of the inside of the neuron with respect to the outside, making it less likely to fire. When a neurotransmitter from the presynaptic neuron crosses the synapse, finds an appropriate receptor site on the postsynaptic neuron, and binds, a voltage change occurs. This voltage change in the postsynaptic neuron is not an all-or-none, the neuron will fire or it won�t, kind of thing. Instead, it changes the probability or potential that the postsynaptic neuron will fire. This is, therefore, called a postsynaptic potential. The postsynaptic potential can be excitatory or inhibitory. An excitatory potential makes the neuron more likely to fire�decreases the negativity of the inside of the neuron with respect to the outside. An inhibitory postsynaptic potential increases the negativity of the inside of the neuron with respect to the outside, making it less likely to fire.

15. Signals: From Postsynaptic Potentialsto Neural Networks One neuron, signals from thousands of other neurons Requires integration of signals PSPs add up, balance out Balance between IPSPs and EPSPs Neural networks Patterns of neural activity Interconnected neurons that fire together or sequentially One neuron may receive signals from thousands of other neurons, across thousands of different synapses. Each neuron must integrate the many signals arriving at the same time before it �decides� to fire. EPSPs together add up�enough can cause the cell�s voltage to reach the threshold at which the action potential will begin. EPSPs and IPSPs may balance out, as well, and the neuron would remain at rest. Thus, the state of the neuron is a weighted balance. Thought occurs through the firing of millions of neurons in unison. Our perceptions, thoughts, and actions depend on patterns of neural activity in interconnected neurons that fire together or sequentially � neural networks. The links in these networks are constantly changing, with synaptic pruning or the elimination of old or unused synapses playing a larger role than the creation of new synapses in the sculpting of neural networks. For example, the number of synapses in the human visual cortex begins to decline after the age of 1 year. One neuron may receive signals from thousands of other neurons, across thousands of different synapses. Each neuron must integrate the many signals arriving at the same time before it �decides� to fire. EPSPs together add up�enough can cause the cell�s voltage to reach the threshold at which the action potential will begin. EPSPs and IPSPs may balance out, as well, and the neuron would remain at rest. Thus, the state of the neuron is a weighted balance. Thought occurs through the firing of millions of neurons in unison. Our perceptions, thoughts, and actions depend on patterns of neural activity in interconnected neurons that fire together or sequentially � neural networks. The links in these networks are constantly changing, with synaptic pruning or the elimination of old or unused synapses playing a larger role than the creation of new synapses in the sculpting of neural networks. For example, the number of synapses in the human visual cortex begins to decline after the age of 1 year.

16. Signals: From Postsynaptic Potentialsto Neural Networks Synaptic connections Elimination and creation Synaptic pruning One neuron may receive signals from thousands of other neurons, across thousands of different synapses. Each neuron must integrate the many signals arriving at the same time before it �decides� to fire. EPSPs together add up�enough can cause the cell�s voltage to reach the threshold at which the action potential will begin. EPSPs and IPSPs may balance out, as well, and the neuron would remain at rest. Thus, the state of the neuron is a weighted balance. Thought occurs through the firing of millions of neurons in unison. Our perceptions, thoughts, and actions depend on patterns of neural activity in interconnected neurons that fire together or sequentially � neural networks. The links in these networks are constantly changing, with synaptic pruning or the elimination of old or unused synapses playing a larger role than the creation of new synapses in the sculpting of neural networks. For example, the number of synapses in the human visual cortex begins to decline after the age of 1 year. One neuron may receive signals from thousands of other neurons, across thousands of different synapses. Each neuron must integrate the many signals arriving at the same time before it �decides� to fire. EPSPs together add up�enough can cause the cell�s voltage to reach the threshold at which the action potential will begin. EPSPs and IPSPs may balance out, as well, and the neuron would remain at rest. Thus, the state of the neuron is a weighted balance. Thought occurs through the firing of millions of neurons in unison. Our perceptions, thoughts, and actions depend on patterns of neural activity in interconnected neurons that fire together or sequentially � neural networks. The links in these networks are constantly changing, with synaptic pruning or the elimination of old or unused synapses playing a larger role than the creation of new synapses in the sculpting of neural networks. For example, the number of synapses in the human visual cortex begins to decline after the age of 1 year.

18. Neurotransmitters Specific neurotransmitters work at specific synapses Lock and key mechanism Agonist � mimics neurotransmitter action Antagonist � opposes action of a neurotransmitter 15 � 20 neurotransmitters known at present Interactions between neurotransmitter circuits NTs deliver their messages by binding to a receptor site�in a lock and key type manner. Not just any receptor site will do�there must be a perfect fit between the shape of the NT and the shape of the receptor site. Some drugs mimic neurotransmitters, fitting into receptor sites so perfectly that the site is fooled and a PSP is set up�these chemicals are called agonists. Other chemicals oppose the action of a NT�they bind to the receptor site but don�t really fit well enough to �fool� the site�they just block it. Right now, we know of about 15-20 substances that qualify as NTs�5 are commonly researched. While research has outlined many interesting connections between neurotransmitters and behavior, most aspects of behavior are probably regulated by many neurotransmitters interacting. NTs deliver their messages by binding to a receptor site�in a lock and key type manner. Not just any receptor site will do�there must be a perfect fit between the shape of the NT and the shape of the receptor site. Some drugs mimic neurotransmitters, fitting into receptor sites so perfectly that the site is fooled and a PSP is set up�these chemicals are called agonists. Other chemicals oppose the action of a NT�they bind to the receptor site but don�t really fit well enough to �fool� the site�they just block it. Right now, we know of about 15-20 substances that qualify as NTs�5 are commonly researched. While research has outlined many interesting connections between neurotransmitters and behavior, most aspects of behavior are probably regulated by many neurotransmitters interacting.

20. Organization of the Nervous System Central nervous system (CNS) Afferent = toward the CNS Efferent = away from the CNS Peripheral nervous system Somatic nervous system Autonomic nervous system (ANS) Sympathetic Parasympathetic The nervous system has two main divisions, central and peripheral. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of nerves that lie outside the brain and spinal cord. In the peripheral nervous system, afferent nerve fibers send information toward the CNS, while efferent nerve fibers send information away from the CNS. There are two divisions of the peripheral nervous system, the somatic, or voluntary portion, and the autonomic, or involuntary portion. The autonomic portion of the peripheral nervous system governs involuntary, visceral functions�such as heart and breathing rate, blood pressure, etc. When a person is autonomically aroused, these speed up. This speeding up is controlled by the sympathetic division of the autonomic nervous system�the sympathetic nervous system mobilizes the body�s resources for emergencies and creates the fight-or-flight response. The parasympathetic division, in contrast, activates processes that conserve bodily resources�slowing heart rate, reducing blood pressure, etc. The nervous system has two main divisions, central and peripheral. The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of nerves that lie outside the brain and spinal cord. In the peripheral nervous system, afferent nerve fibers send information toward the CNS, while efferent nerve fibers send information away from the CNS. There are two divisions of the peripheral nervous system, the somatic, or voluntary portion, and the autonomic, or involuntary portion. The autonomic portion of the peripheral nervous system governs involuntary, visceral functions�such as heart and breathing rate, blood pressure, etc. When a person is autonomically aroused, these speed up. This speeding up is controlled by the sympathetic division of the autonomic nervous system�the sympathetic nervous system mobilizes the body�s resources for emergencies and creates the fight-or-flight response. The parasympathetic division, in contrast, activates processes that conserve bodily resources�slowing heart rate, reducing blood pressure, etc.

24. Studying the Brain: Research Methods Electroencephalography (EEG) Damage studies/lesioning Electrical stimulation (ESB) Transcranial magnetic stimulation (TMS) Brain imaging � computerized tomography positron emission tomography magnetic resonance imaging Electroencephalography (EEG) � monitoring electrical activity of the brain Damage studies/lesioning � observing consequences of damage to certain areas Electrical stimulation (ESB) � stimulating a portion of the brain and observing effects Transcranial magnetic stimulation � enhance or suppress activity in a particular region of the brain Brain imaging: computerized tomography � computer enhanced X-ray positron emission tomography � radioactively tagged chemicals serve as markers of blood flow or metabolic activity in the brain that are monitored by X-ray magnetic resonance imaging � uses magnetic fields, radio waves, and computer enhancement to image brain structure Electroencephalography (EEG) � monitoring electrical activity of the brain Damage studies/lesioning � observing consequences of damage to certain areas Electrical stimulation (ESB) � stimulating a portion of the brain and observing effects Transcranial magnetic stimulation � enhance or suppress activity in a particular region of the brain Brain imaging: computerized tomography � computer enhanced X-ray positron emission tomography � radioactively tagged chemicals serve as markers of blood flow or metabolic activity in the brain that are monitored by X-ray magnetic resonance imaging � uses magnetic fields, radio waves, and computer enhancement to image brain structure

25. Brain Regions and Functions Hindbrain � vital functions � medulla, pons, and cerebellum Midbrain � sensory functions � dopaminergic projections, reticular activating system Forebrain � emotion, complex thought � thalamus, hypothalamus, limbic system, cerebrum, cerebral cortex The hindbrain is located at the lower end of the brain, where the spinal cord joins the brainstem. The medulla is in charge of circulation, breathing, muscle tone, and regulating reflexes�the pons is important in sleep and arousal�the cerebellum is critical in the coordination of movement and equilibrium. The midbrain lies between the hindbrain and the forebrain�it is involved in sensory functions such as locating where things are in space. It also contains structures which are important for voluntary movement (Parkinson�s disease is due to degeneration of the substantia nigra, a structure in the midbrain). The reticular activating system is found in both the hind and midbrain, and is important in sleep and arousal as well as breathing and pain perception. The forebrain is the largest and most complex region of the brain. It includes the thalamus � the way station for all incoming sensory information before it is passed on to appropriate higher brain regions�the hypothalamus � which is the regulator of basic biological needs such as hunger, thirst, sex drive, and temperature regulation�the limbic system � which is a loosely connected network of structures involved in emotion, motivation, memory, and other aspects of behavior�and finally, the cerebrum, which is the largest and most complex portion of the human brain�the convoluted outer layer of the cerebrum is the cerebral cortex�the cerebrum is responsible for complex mental activities such as learning, remembering, thinking, and consciousness. The hindbrain is located at the lower end of the brain, where the spinal cord joins the brainstem. The medulla is in charge of circulation, breathing, muscle tone, and regulating reflexes�the pons is important in sleep and arousal�the cerebellum is critical in the coordination of movement and equilibrium. The midbrain lies between the hindbrain and the forebrain�it is involved in sensory functions such as locating where things are in space. It also contains structures which are important for voluntary movement (Parkinson�s disease is due to degeneration of the substantia nigra, a structure in the midbrain). The reticular activating system is found in both the hind and midbrain, and is important in sleep and arousal as well as breathing and pain perception. The forebrain is the largest and most complex region of the brain. It includes the thalamus � the way station for all incoming sensory information before it is passed on to appropriate higher brain regions�the hypothalamus � which is the regulator of basic biological needs such as hunger, thirst, sex drive, and temperature regulation�the limbic system � which is a loosely connected network of structures involved in emotion, motivation, memory, and other aspects of behavior�and finally, the cerebrum, which is the largest and most complex portion of the human brain�the convoluted outer layer of the cerebrum is the cerebral cortex�the cerebrum is responsible for complex mental activities such as learning, remembering, thinking, and consciousness.

26. The Cerebrum:Two Hemispheres, Four Lobes Cerebral Hemispheres � two specialized halves connected by the corpus collosum Left hemisphere � verbal processing: language, speech, reading, writing Right hemisphere � nonverbal processing: spatial, musical, visual recognition The cerebrum is divided into two specialized hemispheres that are connected by the corpus collosum. The corpus collosum is a thick band of fibers (axons) that transmits information between the hemispheres. Researchers using split brain methodology (severing of the corpus collosum) have learned that each hemisphere is specialized for different functions, with left usually dominant for language and right for spatial skills. Each hemisphere has four lobes: occipital � where the primary visual cortex is located, parietal � where the primary somatosensory cortex is located, temporal � where the primary auditory cortex is located, and frontal � where the primary motor cortex and executive control system is located. The cerebrum is divided into two specialized hemispheres that are connected by the corpus collosum. The corpus collosum is a thick band of fibers (axons) that transmits information between the hemispheres. Researchers using split brain methodology (severing of the corpus collosum) have learned that each hemisphere is specialized for different functions, with left usually dominant for language and right for spatial skills. Each hemisphere has four lobes: occipital � where the primary visual cortex is located, parietal � where the primary somatosensory cortex is located, temporal � where the primary auditory cortex is located, and frontal � where the primary motor cortex and executive control system is located.

27. The Cerebrum:Two Hemispheres, Four Lobes Four Lobes: Occipital � vision Parietal - somatosensory Temporal - auditory Frontal � movement, executive control systems The cerebrum is divided into two specialized hemispheres that are connected by the corpus collosum. The corpus collosum is a thick band of fibers (axons) that transmits information between the hemispheres. Researchers using split brain methodology (severing of the corpus collosum) have learned that each hemisphere is specialized for different functions, with left usually dominant for language and right for spatial skills. Each hemisphere has four lobes: occipital � where the primary visual cortex is located, parietal � where the primary somatosensory cortex is located, temporal � where the primary auditory cortex is located, and frontal � where the primary motor cortex and executive control system is located. The cerebrum is divided into two specialized hemispheres that are connected by the corpus collosum. The corpus collosum is a thick band of fibers (axons) that transmits information between the hemispheres. Researchers using split brain methodology (severing of the corpus collosum) have learned that each hemisphere is specialized for different functions, with left usually dominant for language and right for spatial skills. Each hemisphere has four lobes: occipital � where the primary visual cortex is located, parietal � where the primary somatosensory cortex is located, temporal � where the primary auditory cortex is located, and frontal � where the primary motor cortex and executive control system is located.

34. The Endocrine System:Glands and Hormones Hormones � chemical messengers in the bloodstream Pulsatile release by endocrine glands Negative feedback system Endocrine glands Pituitary � �master gland,� growth hormone Thyroid � metabolic rate Adrenal � salt and carbohydrate metabolism Pancreas � sugar metabolism Gonads � sex hormones Hormones are chemical messengers in the bloodstream that are secreted by the endocrine glands in a pulsatile manner � that is, several times per day in brief bursts or pulses. The levels of many hormones increase to a certain level, then signals are sent to the hypothalamus or other endocrine glands to stop secretion of that hormone � a negative feedback system. These glands include: the pituitary � the master gland that secretes substances influencing the operation of all the other glands, as well as growth hormone; the thyroid gland � which controls metabolic rate; the adrenal glands � which control salt and carbohydrate metabolism; the pancreas � which secretes insulin to control sugar metabolism; and the gonads � which secrete sex hormones involved in the development of secondary sex characteristics and reproduction. Hormones are chemical messengers in the bloodstream that are secreted by the endocrine glands in a pulsatile manner � that is, several times per day in brief bursts or pulses. The levels of many hormones increase to a certain level, then signals are sent to the hypothalamus or other endocrine glands to stop secretion of that hormone � a negative feedback system. These glands include: the pituitary � the master gland that secretes substances influencing the operation of all the other glands, as well as growth hormone; the thyroid gland � which controls metabolic rate; the adrenal glands � which control salt and carbohydrate metabolism; the pancreas � which secretes insulin to control sugar metabolism; and the gonads � which secrete sex hormones involved in the development of secondary sex characteristics and reproduction.

35. Genes and Behavior:The Field of Behavioral Genetics Behavioral genetics = the study of the influence of genetic factors on behavioral traits Chromosomes � strands of DNA carrying genetic information Human cells contain 46 chromosomes in pairs (sex-cells � 23 single) Each chromosome � thousands of genes, also in pairs Dominant, recessive Homozygous, heterozygous Genotype/Phenotype and Polygenic Inheritance Questions about how much of behavior is biologically based and how much is environmentally based are very old ones in psychology. Since the 1970�s, however, research methodologies have been developed in the field of behavioral genetics that shed new light on the age-old nature vs. nurture question. Basic terminology necessary to discuss behavior genetics research: Chromosomes are strands of Deoxyribonucleic Acid (DNA) carrying genetic information�each human cell contains 23 pairs, or 46 total, chromosomes�with the exception of sex cells which have 23 single chromosomes�not yet paired. Each chromosome contains thousands of genes, which also occur in pairs�sometimes a member of a pair has a louder voice, always expressing itself and masking the other, different, member of the pair�this is a dominant gene. A recessive gene is one that is masked when the paired genes are different. When a person has two genes in a specific pair that are the same, the person is homozygous for that trait�if the genes are different, heterozygous Genotype refers to a person�s genetic makeup, while phenotype refers to the ways in which a person�s genotype is manifested in observable characteristics. You can have different genotypes which yield the same phenotype (i.e., one person has 2 genes for detached earlobes (dominant) while another has one for attached and one for detached�both, outwardly, look the same in the earlobe department)�most human traits are not so simple with regard to genetic transmission�they are polygenic, or influenced by more than one pair of genes. Questions about how much of behavior is biologically based and how much is environmentally based are very old ones in psychology. Since the 1970�s, however, research methodologies have been developed in the field of behavioral genetics that shed new light on the age-old nature vs. nurture question. Basic terminology necessary to discuss behavior genetics research: Chromosomes are strands of Deoxyribonucleic Acid (DNA) carrying genetic information�each human cell contains 23 pairs, or 46 total, chromosomes�with the exception of sex cells which have 23 single chromosomes�not yet paired. Each chromosome contains thousands of genes, which also occur in pairs�sometimes a member of a pair has a louder voice, always expressing itself and masking the other, different, member of the pair�this is a dominant gene. A recessive gene is one that is masked when the paired genes are different. When a person has two genes in a specific pair that are the same, the person is homozygous for that trait�if the genes are different, heterozygous Genotype refers to a person�s genetic makeup, while phenotype refers to the ways in which a person�s genotype is manifested in observable characteristics. You can have different genotypes which yield the same phenotype (i.e., one person has 2 genes for detached earlobes (dominant) while another has one for attached and one for detached�both, outwardly, look the same in the earlobe department)�most human traits are not so simple with regard to genetic transmission�they are polygenic, or influenced by more than one pair of genes.

37. Research Methods in Behavioral Genetics Family studies � does it run in the family? Twin studies � compare resemblance of identical (monozygotic) and fraternal (dizygotic) twins on a trait Adoption studies � examine resemblance between adopted children and their biological and adoptive parents Family studies simply assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait�determine whether it runs in the family�many things run in families, however, that are not genetic�like dessert recipes or speaking a certain language. Twin studies can yield better evidence about the possible influence of heredity, because identical twins have the exact same genotype�they share 100% of the same genes. Fraternal twins only share 50% genetic relatedness�the same as any two siblings born to a set of parents at different times. Twins of both types, however, are raised in more similar environments (same age, configuration of relatives, etc.). If identical twins are more similar on a given trait than fraternal, the assumption is that it is probably genetic. Adoption studies assess genetic influence by comparing adopted children with both their biological and adoptive parents�if they are more like their biological parents (who they have never met) on a trait, it is probably genetic.Family studies simply assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait�determine whether it runs in the family�many things run in families, however, that are not genetic�like dessert recipes or speaking a certain language. Twin studies can yield better evidence about the possible influence of heredity, because identical twins have the exact same genotype�they share 100% of the same genes. Fraternal twins only share 50% genetic relatedness�the same as any two siblings born to a set of parents at different times. Twins of both types, however, are raised in more similar environments (same age, configuration of relatives, etc.). If identical twins are more similar on a given trait than fraternal, the assumption is that it is probably genetic. Adoption studies assess genetic influence by comparing adopted children with both their biological and adoptive parents�if they are more like their biological parents (who they have never met) on a trait, it is probably genetic.

41. Modern Approaches to theNature vs. Nurture Debate Molecular Genetics = the study of the biochemical bases of genetic inheritance Genetic mapping � locating specific genes - The Human Genome Project Behavioral Genetics The interactionist model Richard Rose (1995) � �We inherit dispositions, not destinies.� Modern advances in molecular genetic technology have allowed for genetic mapping�the locating of specific chromosomes and genes involved in phenotypic expression. While this is a promising area of research, initial progress points toward the complexity of polygenic inheritance rather than yielding simple answers to the nature nurture debate. The behavioral genetics field has yielded much the same conclusion�there will be no simple answer to the �is it nature or nurture� question�Richard Rose quote � �we inherit dispositions, not destinies.�Modern advances in molecular genetic technology have allowed for genetic mapping�the locating of specific chromosomes and genes involved in phenotypic expression. While this is a promising area of research, initial progress points toward the complexity of polygenic inheritance rather than yielding simple answers to the nature nurture debate. The behavioral genetics field has yielded much the same conclusion�there will be no simple answer to the �is it nature or nurture� question�Richard Rose quote � �we inherit dispositions, not destinies.�

42. Evolutionary Psychology:Behavior in Terms of Adaptive Significance Based on Darwin�s ideas of natural selection Reproductive success key Adaptations � behavioral as well as physical Fight-or-flight response Taste preferences Parental investment and mating The field of evolutionary psychology is a major new field in psychology focusing on analyzing human behavior in terms of adaptive significance. Based on the work of Charles Darwin and the ideas of natural selection and reproductive fitness�i.e., that variations in reproductive success are what really fuels evolutionary change. Evolutionary theorists study adaptations, or inherited characteristics, that increase in a population because they help solve a problem of survival or reproduction during the time they emerge�giraffes and long necks. May extend even when no longer needed, for example the fight-or-flight response may have been very helpful in primitive times, but now it is related to a number of stress-related diseases. Similarly, humans show a taste preference for fatty foods�this was adaptive in a hunter/gatherer society, when dietary fat was scarce�before potato chips, etc.�resulting in obesity, heart disease, etc. While this may lead to decreased longevity, the effect on reproductive success is more difficult to gauge. Parental investment refers to time, energy, survival risk, and forgone opportunities that each sex has to invest in order to produce and nurture offspring. Trivers (1972) suggests that a species courting and mating patterns are based in parental investment. When parental investment is high for females and low for males, polygyny results � a mating system whereby each male seeks to mate with multiple, females and each female seeks only one male. Polyandry occurs when each female seeks to mate with multiple males and each male with only one female � this emerges when parental investment is high for males and low for females. Monogamy emerges when male and female parental investment is roughly equal.The field of evolutionary psychology is a major new field in psychology focusing on analyzing human behavior in terms of adaptive significance. Based on the work of Charles Darwin and the ideas of natural selection and reproductive fitness�i.e., that variations in reproductive success are what really fuels evolutionary change. Evolutionary theorists study adaptations, or inherited characteristics, that increase in a population because they help solve a problem of survival or reproduction during the time they emerge�giraffes and long necks. May extend even when no longer needed, for example the fight-or-flight response may have been very helpful in primitive times, but now it is related to a number of stress-related diseases. Similarly, humans show a taste preference for fatty foods�this was adaptive in a hunter/gatherer society, when dietary fat was scarce�before potato chips, etc.�resulting in obesity, heart disease, etc. While this may lead to decreased longevity, the effect on reproductive success is more difficult to gauge. Parental investment refers to time, energy, survival risk, and forgone opportunities that each sex has to invest in order to produce and nurture offspring. Trivers (1972) suggests that a species courting and mating patterns are based in parental investment. When parental investment is high for females and low for males, polygyny results � a mating system whereby each male seeks to mate with multiple, females and each female seeks only one male. Polyandry occurs when each female seeks to mate with multiple males and each male with only one female � this emerges when parental investment is high for males and low for females. Monogamy emerges when male and female parental investment is roughly equal.