1. The Biology of Behavior
Chapter 2
The Biology of Behavior
PowerPoint® Presentation
by Jim Foley

2. Searching for the biology of “self”
Is our identity in the heart?
In the brain?
In the whole body?
Biological Psychologists explore the associations between body, mind, and behavior.
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Lesson to bring out here: the brain is not a computer, or a mind, or identity which is separate from the rest of the body; it is all interconnected, as we soon shall see.

3. Overview: What We Have in Mind
Building blocks of mind: Neurons and how they communicate (neurotransmitters)
Systems that build the mind: Functions of Parts of the Nervous system
Supporting player: the slower-communicating Endocrine system (hormones)
Tools for examining the brain and its activities
More primitive and advanced brain structures
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4. Neural and Hormonal Systems

5. Neurons and Neuronal Communication: The Structure of a Neuron
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Most of the neurons are in the brain but there are motor and sensory neurons throughout the body. The message does not travel down the axon in the same way an electrical signal does down a wire; in fact electricity in a wire travels 3 million times faster. In the body, neural signals travel about 2 to 180 miles per hour. However, the chemical signal has an advantage; it does not decrease in intensity as it travels down the axon. No signal is lost.
You could demonstrate speed of signal transmission by having it travel across all the students hand to brain to hand across the room (or hand to shoulder to possibly bypass the brain).
Note the myelin sheath. Multiple sclerosis involves the degeneration of this layer, thus interfering with neural communication with muscles and other areas.
There are billions of neurons
(nerve cells) throughout the body.

6. Action potential: a neural impulse that travels down an axon like a wave
Just as “the wave” can flow to the right in a stadium even though the people only move up and down, a wave moves down an axon although it is only made up of ion exchanges moving in and out.
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Note: with both the stadium example and the action potential example, no physical object actually flows in any direction when the wave flows.
The action potential is the area that is briefly charged by the net intake of positive ions; this is the traveling “electrical charge” created when channels in the cell membrane quickly allow positive ions in, and then more slowly pump the ions out again as the wave moves on.
The fans in the stadium create the wave by standing up briefly; the cell membrane creates a wave by pumping positive ions in briefly. This could be the subject of a demonstration in class.

7. How neurons communicate (with each other):
When does the cell send the action potential? When it reaches a threshold.
How neurons communicate (with each other):
The neuron receives signals from other neurons; some are telling it to fire and some are telling it not to fire.
When the threshold is reached, the action potential starts moving.
Like a gun, it either fires or it doesn’t; more stimulation does nothing.
This is known as the “all-or-none” response.
The action potential travels down the axon from the cell body to the terminal branches.
The signal is transmitted to another cell. However, the message must find a way to cross a gap between cells. This gap is also called the synapse.
Click to show each stage in the path.
If signals only have one level of intensity, then why does a punch hurt more than a tap? Because in the case of the punch, more neurons are firing.
The threshold is reached when excitatory (“Fire!”) signals outweigh the inhibitory (“Don’t fire!”) signals by a certain amount.

8. The Synapse
The synapse is a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron.
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The synapse is also known as the “synaptic junction” or “synaptic gap.”

9. Neurotransmitters
Neurotransmitters are chemicals used to send a signal across the synaptic gap.
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Neurotransmitters are released from the sending neuron and stimulate receptor sites on the receiving neuron. These are the signals telling the receiving cell whether or not to fire the next action potential.

10. Reuptake: Recycling Neurotransmitters [NTs]
Reuptake: After the neurotransmitters stimulate the receptors on the receiving neuron, the chemicals are taken back up into the sending neuron to be used again.
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Reuptake ends the transmission of the signal.
Medications which inhibit this reuptake process help ensure that the signal gets transmitted. SSRIs help reduce depression by increasing serotonin levels at the synapse this way, and most ADHD medications such as Ritalin work by blocking the transport of dopamine back into the sending neuron.

11. Seeing all the Steps Together
Neural Communication:
Seeing all the Steps Together
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12. Roles of Different Neurotransmitters
Some Neurotransmitters and Their Functions
Neurotransmitter
Function
Problems Caused by Imbalances
Serotonin
Affects mood, hunger, sleep, and arousal
Undersupply linked to depression; some antidepressant drugs raise serotonin levels
Dopamine
Influences movement, learning, attention, and emotion
Oversupply linked to schizophrenia; undersupply linked to tremors and decreased mobility in Parkinson’s disease and ADHD
Acetylcholine (ACh)
Enables muscle action, learning, and memory
ACh-producing neurons deteriorate as Alzheimer’s disease progresses
Click to reveal each row.
There are some uses/functions that are not mentioned, such as the role of inadequate norepinephrine and dopamine in ADHD.
Note: Some antidepressants, by blocking reuptake of serotonin, raise serotonin levels at the synapse; they don’t add more serotonin to the body.
The problem in schizophrenia may actually be an overabundance of dopamine receptors, not just an oversupply of dopamine itself.
Norepinephrine
Helps control alertness and arousal
Undersupply can depress mood and cause ADHD-like attention problems
GABA gamma-aminobutyric acid
A major inhibitory neurotransmitter
Undersupply linked to seizures, tremors, and insomnia
Glutamate
A major excitatory neurotransmitter; involved in memory
Oversupply can overstimulate the brain, producing migraines or seizures; this is why some people avoid MSG (monosodium glutamate) in food

13. Serotonin pathways Dopamine pathways
Networks of neurons that communicate with serotonin help regulate mood.
Networks of neurons that communicate with dopamine are involved in focusing attention and controlling movement.
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14. Divisions of the Nervous System
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Note that the autonomic, somatic, sympathetic, and parasympathetic branches of the nervous system are all part of the PNS.

15. The Inner and Outer Parts of the Nervous System
The Peripheral Nervous System (CNS), gathers information from the body and sends CNS decisions out to the body.
The Central Nervous System (CNS), the brain and spinal cord, is the body’s decisionmaker.
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16. Types of Neurons
Sensory neurons carry messages IN from the body’s tissues and sensory receptors to the CNS for processing.
Motor neurons carry instructions OUT from the CNS out to the body’s tissues.
Interneurons (in the brain and spinal cord) process information between the sensory input and motor output.
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There are millions of sensory neurons and millions of motor neurons, but BILLIONS of interneurons.

17. The Peripheral Nervous System
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18. The Autonomic Nervous System:
The sympathetic NS arouses (fight-or-flight) The parasympathetic NS calms (rest and digest)
No animation. 1. Question to ask students: Why not just stay aroused all the time?...to allow the body to repair itself and regain energy from food.
2. Comment to students: note the sympathetic nervous system’s effect on the stomach and bladder., This helps us understand why “I was so upset that I wet my pants” or “I was so upset I threw up.” Now you can take these reports as a sign of strong activation of the sympathetic part of the autonomic nervous system.

19. Neural Networks
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These neural networks are activated when needed for action.
These complex webs of interconnected neurons form with experience. Remember: “Neurons that fire together, wire together.”

20. Interneurons in the Spine Decisions made without the brain
Your spine’s interneurons trigger your hand to pull away from a fire before you can say OUCH!
This is an example of a reflex action.
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You not only won’t have time to say “ouch,” you won’t even think it. This is because before the brain gets the pain message, the interneurons in the spinal cord are already sending a message back through motor neurons saying, “pull your hand away!”
The brain finds out about the reflex after it happens.

21. The Endocrine System The endocrine system:
a set of glands that produce chemical messengers called hormones.
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Instead of sending messages across the synapse, the endocrine system sends messages through the bloodstream. The nervous system and the endocrine systems are connected and influence each other. Endocrine system messages travel more slowly but also last longer.

22. The Body’s “Slow but Sure” Endocrine Message System
The endocrine system sends molecules as messages, just like the nervous system, but it sends them through the bloodstream instead of across synapses.
These molecules, called hormones, are produced in various glands around the body.
The messages go to the brain and other tissues.
Pituitary gland
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“Slow but sure” endocrine system messages take longer to get to their location, but then the molecules hang around for a bit, so the effect of the “message” lasts longer. In neural communication, reuptake of the neurotransmitters sometimes prevents effective communication. (This is the real “chemical imbalance” treated by some medication: slowing reuptake.)
The pituitary gland is the “master gland” of the endocrine system.
It is controlled through the nervous system by the nearby brain area--the hypothalamus.
The pituitary gland produces hormones that regulate other glands.

23. Tools of Discovery and Brain Structures
What We’ll See:
How we learn about the brain:
Scans and more
The primitive, life- sustaining, inner parts of the brain:
The brainstem and limbic system
Higher Brain structure that help us think and act:
The Cerebral Cortex
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24. Monitoring activity in the brain
Tools to read electrical, metabolic, and magnetic activity in the brain:
EEG: electroencephalogram
PET: positron emission tomography
Click to show four bubbles.
MRI: magnetic resonance imaging
fMRI: functional MRI

25. EEG: electroencephalogram
An EEG (electroencephalogram) is a recording of the electrical waves sweeping across the brain’s surface.
An EEG is useful in studying seizures and sleep.
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EEGs use electrodes placed on the scalp.

26. PET: positron emission tomography
The PET scan allows us to see what part of the brain is active by tracing where a radioactive form of glucose goes while the brain performs a given task.
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27. MRI: magnetic resonance imaging
fMRI: functional MRI
MRI (magnetic resonance imaging) makes images from signals produced by brain tissue after magnets align the spin of atoms.
The arrows below show ventricular enlargement in a schizophrenic patient (right).
Functional MRI reveals brain activity and function rather than structures.
Functional MRI compares successive MRI images taken a split second apart, and shows changes in the level of oxygen in bloodflow in the brain.
Click to reveal Functional MRI information.

28. The Brain: Less Complex Brain Structures
Our tour of the brain begins with parts of the human brain found also in simpler animals; these parts generally deal with less complex functions:
Brainstem (Pons and Medulla)
Thalamus
Reticular Formation
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Cerebellum
Limbic System

29. The Brainstem: Pons and Medulla
Click to “grow” a subsection view of the brainstem.
The brain’s innermost region begins where the spinal cord enters the skull.

30. The Base of the Brainstem: The Medulla
The medulla controls the most basic functions such as heartbeat and breathing.
Someone with total brain damage above the medulla could still breathe independently, but someone with damage in this area could not.
Click to reveal second bullet.
Christopher Reeve ( ; an image of him here might work well), an actor in Superman movies and Smallville, couldn’t breathe on his own after a horse riding accident broke his spine at the level of the medulla.

31. The Thalamus
The thalamus is the “sensory switchboard” or “router”: All sensory messages, except smell, are routed through the thalamus on the way to the cortex (outer brain).
These messages cross over from one side of the body to the opposite side of the brain.
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The book says “switchboard,” but perhaps it’s time to upgrade the term to “router.”
Damage to the thalamus can cause blindness and other loss of the senses, even if the sensory organ is fine.
However, damage to the thalamus could not hurt your sense of smell, which bypasses the thalamus and goes straight to the olfactory bulb in the brain.
The crossover

32. Reticular (“net-like”) Formation
The reticular formation is a nerve network in the brainstem.
It enables alertness (arousal); stimulating this makes us wide awake.
It also filters incoming sensory information and relays it to other brain areas.
Click to reveal bullets.
Additional information/lecture material:
The structure of the reticular formation: this network of neurons branches from the spinal cord up into the thalamus. I have added two lines to the picture to indicate this.
How do we know about arousal? In the cat experiments, researchers stimulated the reticular formation in order to make a sleeping cat pop awake. Similarly, cutting the reticular formation made a cat lapse into a permanent coma.
About the filtering: it could be said that the reticular formation controls selective awareness; it ‘selects’ which incoming information to send to other brain areas. This enables us to follow a conversation in a crowd, i.e. to select a “signal” out of sensory “noise.”

33. Cerebellum (“little brain”)
The cerebellum helps coordinate voluntary movement such as playing a sport.
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The cerebellum is located in two parts, behind the pons and below the back of the brain.
The cerebellum also is the area where implicit memories and conditioning are stored. It also helps us judge time, modulate emotions, and integrate multiple sources of sensory input.
The cerebellum has many other functions, including enabling nonverbal learning and memory.

34. The Limbic (“Border”) System
The limbic system coordinates:
emotions such as fear and aggression.
basic drives such as hunger and sex.
the formation of episodic memories.
The hippocampus (“seahorse”)
processes conscious, episodic memories.
works with the amygdala to form emotionally charged memories.
The Amygdala (“almond”)
consists of two lima bean- sized neural clusters.
helps process emotions, especially fear and aggression.
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The limbic system is located on the “border”/limbus between the brainstem and cortex; it is between the least complex and most advanced brain structures and between the cerebral hemispheres.
The hippocampus is one of the few places in the brain in which neurogenesis is known to take place.
Stimulating different parts of the amygdala triggers different versions of the defensive, self-protective emotions; one part increases aggressive reactions, while another increases fearful withdrawal. Destruction of part of the amygdala can apparently eliminate both emotions.
Note: aggression and fear reactions involve networks across the brain, and these reactions can be stimulated elsewhere.
The pituitary gland is in the text image, but I faded and shrank the label because it is not really part of the limbic system; I’ll restore it when talking about the hypothalamus.

35. The Amygdala: Enabling two different responses to threat
Electrical stimulation of one area of a cat’s amygdala provokes aggressive reactions.
If you stimulate a different part of the amygdala and put the cat in a cage with a mouse, the cat will cower in terror.
Click to reveal bullets.

36. The Hypothalamus: The Hypothalamus as a Reward Center
lies below (“hypo”) the thalamus.
regulates body temperature and ensures adequate food and water intake (homeostasis), and is involved in sex drive.
directs the endocrine system via messages to the pituitary gland.
Thalamus
The Hypothalamus as a Reward Center
Riddle: Why did the rat cross the grid?
Why did the rat want to get to the other side?
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If you lesion one part of the hypothalamus of a rat, it stops eating; lesion another part and it hardly stops eating.
Click to reveal ‘Hypothalamus Reward Center’ riddle. Click again for answer.
Instructor: After addressing the riddle on the slide, but before adding the additional lecture material below, consider throwing out a question, “So where on this screen is the reward center?. Is it here, (point to the cage), the place to go to get rewards? Oh, it’s up here? (point to the hypothalamus).” [This is where you could note, as below, that there are other reward centers…]
Additional lecture material:
There are other reward centers, including an area near the hypothalamus, the nucleus accumbens.
Many of these areas rely on dopamine, which may be why people with low dopamine (ADHD) don’t learn well from rewards, and why people who crave dopamine (ADHD, addicts, young teens, and those with reward deficiency syndrome) are reckless in their search for it, maybe even crossing an electrified grid like the rat in the illustration.
Pushing the pedal that stimulated the electrode placed in the hypothalamus was much more rewarding than food pellets.

37. Review of Brain Structures
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38. Higher Brain, Split Brain Topics for your cortex to process:
Cerebral Cortex Structure: The Lobes
The motor and sensory strips and association areas
Brain Plasticity
Functioning of he right and left hemispheres from cases of the divided and intact brains
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39. The Cerebral Cortex:
The outer grey “bark” structure that is wrinkled in order to create more surface area for 20+ billion neurons.
Organized into 4 lobes in each of two hemispheres.
300 billion synaptic connections
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The orange area is the cerebellum.
The brain has left and right hemispheres

40. The Lobes of the Cerebral Cortex: Preview
involved in speaking and muscle movements and in making plans and judgments
Frontal Lobes
Parietal Lobes
Occipital Lobes
Temporal Lobes
include the sensory cortex
include the visual areas; they receive visual information from the opposite visual field
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include the auditory processing areas

41. Functions of the Brain: The Motor and Sensory Strips
Input: Sensory cortex (Left hemisphere section receives input from the body’s right side)
Output: Motor cortex (Left hemisphere section controls the body’s right side)
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The body parts along each strip represent the amount of neural space devoted to movement or sensation of that body part. Parts needing more precise sensation or control take up more cortical space.
These “strips” are located at the border of the frontal lobe and the parietal lobe.
 Axons receiving motor signals FROM the cortex
Axons sending sensory information TO the cortex

42. Sensory Functions of the Cortex
The sensory strip deals with information from touch stimuli.
The occipital lobe deals with visual information.
Auditory information is sent to the temporal lobe.
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Auditory areas are also active when someone in a psychotic state is experiencing “voices”/auditory hallucinations

43. The Visual Cortex
This fMRI scan shows increased activity in the visual cortex when a person looks at a photograph.
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44. Association function of the cortex
More complex animals have more cortical space devoted to integrating/associating information
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The relative proportion of the cortex devoted to taking in sensory information and sending out motor commands is smaller as the association areas are larger (a negative correlation).

45. Case study: Phineas Gage
In a work accident, a metal rod shot up through Phineas Gage’s skull, destroying his eye and part of his frontal lobes. After healing, he was rude, odd, irritable, and unpredictable. Possible explanation for the change in personality: Damage to his frontal lobes hurt his ability to inhibit emotions and impulses.
The possible explanation appears with a click.
See if students can guess at an explanation for Gage’s symptoms based on the area of brain damage.

46. Whole-brain Association Activity
Whole-brain association activity involves complex activities which require communication among association areas across the brain such as:
memory
language
attention
meditation and spirituality
consciousness
Click to reveal list.

47. Plasticity: The Brain is Adaptable
This 6-year-old had a hemispherectomy to end life-threatening seizures; her remaining hemisphere compensated for the damage.
If the brain is damaged, especially in the general association areas of the cortex:
the brain does not repair damaged neurons, BUT it can restore some functions
it can form new connections, reorganize, reassign brain areas to new functions.
Some neurogenesis, production of new brain cells, helps rebuild
Click to reveal bullets and example.
Despite lists of lateralized functions, there are many areas of overlap and duplication in the hemispheres. This is part of the reason that the girl with only one hemisphere was able to adapt.

48. Split-
Brain Studies
To end severe whole-brain seizures, some people have had surgery to cut the corpus callosum, a band of axons connecting the hemispheres.
Click to reveal two sentences.
Researchers have studied the impact of this surgery on patients’ functioning.

49. Separating the Hemispheres: Factors to Keep in Mind
Each hemisphere controls the opposite side of the body AND is aware of the visual field on that opposite side.
Without the corpus callosum, the halves of the body and the halves of the visual field do not work together.
Only the left half of the brain has enough verbal ability to express its thoughts out loud.
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Before going on to the next three slides, see if students can speculate on the implications of these three factors. What happens when a person with separated hemispheres tries to read a sign, or reach for something, or describe what he or she sees?

50. Split visual field
Each hemisphere perceives the half of the view in front of you that goes with the half of the body that is controlled by that hemisphere.
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Notice that the optic chiasm is not cut when the corpus callosum is cut.
Instructor: you may want to switch the text, move the slide’s bullet point to the notes and the note to the slide.

51. Divided Awareness in the Split Brain Try to explain the following result:
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See if the students can piece it together: the left hemisphere is the one that does verbal language, and that hemisphere is processing the right visual field, so what it can verbally report is “Art.”

52. The divided brain in action
Talent: people are able to follow two instructions and draw two different shapes simultaneously
Drawback: people can be frustrated that the right and left sides do different things
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People with ‘divided brains’ may be more likely to report frustration with what the LEFT hand is doing; see if students can figure out why that is (the left hemisphere is the one talking to you and doesn’t know what input or purposes the right hemisphere is acting on).

53. Our Two Hemispheres Lateralization (“going to one side”)
The two hemispheres serve some different functions. How do we know about these differences?
Brain damage studies revealed many functions of the left hemisphere.
Brain scans and split brain studies show more about the functions of the two hemispheres, and how they coordinate with each other.
Click to reveal bullets.
Brain scan studies show normal individuals engage their right brain when completing a perceptual task and their left brain when carrying out a linguistic task. However, many functions of the two hemispheres overlap.

54. The intact but lateralized brain Right-Left Hemisphere Differences
Right Hemisphere
Feelings and intuition
Language: tone, inflection, context
Wholes, including the self
Thoughts and logic
Language: words and definitions
Pieces and details
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I’ve included this here rather than later because it helps with understanding the split brain studies.
Note (from the “Handedness” close-up box in the text): about 3 percent of people, mostly lefties, do not follow this pattern as clearly, e.g. they process language in the right, or both, hemispheres.

55. Behavior Genetics and Evolutionary Psychology

56. Behavior Genetics: Predicting Individual Differences
Behavior geneticists
study how heredity and environment contribute to human differences.
More ways of exploring the origins of the biology of behavior:
Understanding genes
Twin and adoption studies
Gene/environment interactions
Evolutionary Psychology
Let’s start by looking at GENES.
Click to show Behavior geneticists box.
Instructor: Behavior geneticists study how heredity and environment contribute to human differences. Following this slide is an optional slide in case you want that definition on screen. The book words it differently: “Behavior geneticists study our differences and weigh the interplay of heredity and environment.”
Using the word “predicting” here instead of “explaining” is a different standard as we assemble our evidence into theories. We hope to not only come up with descriptions that include reasons, but to understand patterns well enough that we can predict what will happen.
The focus in this section is on the tools we can use to explore the “nature” side of the equation; later we will look at cultural and other environmental influences on the brain, gender roles, and other traits and behaviors. We will wait until a later chapter to explore and possibly explain or predict individual and group differences in intelligence.

57. The Building Blocks of Heredity and Development GENES:
Genes are parts of DNA molecules, which are found in chromosomes in the nuclei of cells.
Genes are parts of DNA molecules, which are found in chromosomes in the nuclei of cells.
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DNA
(Deoxyribonucleic Acid)

58. Chromosomes are made of DNA, which are made of genes.
Chromosome: threadlike structure made largely of DNA molecules
DNA:
a spiraling, complex molecule containing genes
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59. Chromosomes and Inheritance
The human genome includes 46 chromosomes in 23 sets matched sets; each chromosome has the same gene locations.
This includes the X and Y chromosomes, not a matched set in males, who are missing some genes on the Y.
A biological parent donates half his/her set of chromosomes to his/her offspring.
We received half a set of chromosomes from each biological parent.
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60. The Human Genome: 20,000 to 25,000 Genes
The genome: an organism’s entire collection of genes
Human genomes are so nearly identical that we can speak of one universal human genome.
Yet tiny genetic differences make a difference. If there is a:
.001 percent difference in genome, your DNA would not match the crime scene/you are not the baby’s father.
0.5 to 4 percent difference in genome, you may be a chimpanzee.
50 percent difference in genome, you may be a banana.
Click to reveal bullets.

61. How Genes Work Genes are not blueprints; they are molecules.
These molecules have the ability to direct the assembly of proteins that build the body.
This genetic protein assembly can be turned on and off by the environment, or by other genes.
Any trait we see is a result of the complex interactions of many genes and countless other molecules.
Click to reveal bullets.
Note: there is rarely one single gene for one trait, and tiny differences in genes can influence big differences in appearance and behavior.

62. Next step for behavior geneticists: Controlling Variables
Can we design an experiment to keep genes constant and vary the environment and see what happens?
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Answer to these questions:
Not exactly, but we can observe what has happened when those circumstances have arisen, such as in twin and adoption studies.
Or vary the genes in the same environment?

63. Fraternal and Identical Twins
Twin and Adoption Studies
To assess the impact of nature and nurture, how do we examine how genes make a difference within the same environment?
study traits of siblings vs. identical twins
see if the siblings vary more than twins
Fraternal “twins” from separate eggs are not any more genetically alike than other siblings.
Identical twin: Same sex only
Click to reveal sidebar.
Fraternal twins are more alike than other siblings, however, in the home environment they share. They are raised at the same time in their parents’ lives, with the same number and age of siblings.
Even identical twins, though, can have biological differences, if they have separate placentas (this happens in about one out of three times) and thus get different nourishment.
Fraternal twin: Same or opposite sex

64. Identical vs. Fraternal Twins
Twin and Adoption Studies
How do we find out how the same genes express themselves in different environments?
We can study the traits of identical twins as they grow up, or if they were raised separately (e.g., the Minnesota Twin Family Study).
Studies of twins in adulthood show that identical twins are more alike than fraternal twins in:
personality traits such as extraversion (sociability) and neuroticism (emotional instability).
behaviors/outcomes such as the rate of divorce.
abilities such as overall Intelligence test scores.
Click to reveal sidebar.
Instructor: In these and related studies, not only are identical twins more alike than fraternal twins, but fraternal twins are more alike than random strangers even though random strangers are also raised in different environments.
Question for the students, in this slide and the next: which factor is being controlled here, and which factor is varying? [Answer: presumably, these studies are done on twins raised at first together, then having some adult time apart; if fraternal twins have more differences than identical twins, the only factor which has varied is the level of genetic similarity.]

65. Studies of Identical Twins Raised Apart
Critiques of Twin Studies
In the more recent years of the Minnesota Twin Family Study, twins have known about each other and may influence each other to be more similar.
Coincidences happen; some randomly chosen pairs of people will have similar traits.
Environments may be similar; adoptive families tend to be more similar than randomly selected families in education, income, and values.
Similarities found in identical twins despite being raised in different homes:
personality, styles of thinking and relating
abilities/intelligence test scores
attitudes
interests, tastes
specific fears
brain waves, heart rate
Click to reveal bullets, then more in sidebar.
Instructor: There are cases in which identical twins are separated at birth through adoption but are later found to be twins. The Minnesota Twin Family Study is the biggest example of this.
Again, I suggest asking the students: which factor is being controlled here, and which factor is varying?
Sidebar: Another critique is that the environments or “nurture” may be more similar for twins than for a pair of unrelated people because they look identical and thus are treated more similarly.
BUT none of these factors explains, better than the genetic explanation, why fraternal twins have more differences than identical twins.

66. Searching for Parenting Effects: Biological vs. Adoptive Relatives
Studies have been performed with adopted children for whom the biological relatives are known. Findings: Adopted children seem to be more similar to their genetic relatives than their environmental/nurture relatives.
Given the evidence of genetic impact on how a person turns out, does parenting/nurture make any difference?
Does the home environment have any impact?
Click to reveal bullets.

67. Parenting Does Matter
Despite the strong impact of genetics on personality, parenting has an influence on:
religious beliefs
values
manners
attitudes
politics
habits
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68. How does the interaction of genes and environment work?
Example in animals: shortened daylight triggers animals to change fur color or to hibernate
Gene-Environment Interaction: genes turn each other on and off in response to environmental conditions
Epigenetics: The study of how this happens: The environment acts on the surface of genes to alter their activity
Example in humans:
obesity in adults can turn off weight regulation genes in offspring
Click to reveal bullets and examples.
The main mechanism for epigenetic change is the methyl molecule on DNA which essential deactivates it, keeping the gene from coding proteins.
Sample of some of the citations on the obesity result at the bottom:

69. Evolutionary Psychology:
Understanding Human Nature
Some topics:
Natural selection and adaptation
Evolutionary success may help explain similarities
An evolutionary explanation of human sexuality
Evolutionary psychology is the study of how evolutionary principles help explain the origin and function of the human mind, traits, and behaviors.
Click to reveal definition of evolutionary psychology.
Evolutionary principles are used in evolutionary psychology to explain human universals and commonalities; qualities that helped ancestors survive and reproduce and spread those traits in the genes of many offspring.
We have been talking so far about human differences; we may now seek insight in the ways in which humans are alike.

70. Natural Selection: How it Works
Evolutionary Psychology:
Natural Selection: How it Works
Begin with a species’ genome, which contains a variety of versions of genes that shape traits.
Conditions make it difficult for individuals with some traits (some versions of those genes) to survive long enough to reproduce.
Other individuals thus have their traits and genes “selected” to spread in the population.
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71. Artificial Selection The Domesticated Silver Foxes
Dmitri Balyaev and Lyudmila Trut spent 40 years selecting the most gentle, friendly, and tame foxes from a fox population, and having those reproduce.
As a result, they were able to shape avoidant and aggressive creatures into social ones, just as wolves were once shaped into dogs.
Click to reveal bullets.

72. How might evolution have shaped the human species?
Example:
Why does “stranger anxiety” develop between the ages of 9 and 13 months?
Hint: in evolutionary/survival terms, humans are learning to walk at that time.
Infants who used their new ability to walk by walking away from family and toward a lion might not have survived to reproduce as well as those who decided to stay with parents around the time they learned to walk.
Click to reveal bullets. Optional Slide.
Another possible example of evolutionary shaping (from the text): the instinct to dislike bitter foods (which may have been toxic to our ancestors) especially during pregnancy.
Critique of evolutionary psychology: it begins with an effect (stranger anxiety, phobias) and works backward to propose an explanation. It is almost impossible to lose when proposing an explanation in hindsight, and these explanations almost always defy the level of scientific scrutiny and verification suggested in Chapter 1.

73. Evolutionary Psychology’s Explanation of Biologically Driven Phobias
Why do people so easily acquire a phobia of snakes, more easily than a phobia of cars?
An evolutionary psychologist would note that snakes are often poisonous…
…so, those who more readily learned to fear them were more likely to survive and reproduce.
Click to reveal bullets. Optional Slide.
Discussion question: why are clowns such a common phobia? Hint at a possibility: there is evidence that our lineage split away from those that evolved into today’s baboons and mandrills long before our ancestry diverged from today’s chimpanzees or even gorillas and orangutans. Check out a picture of a mandrill…
Critique: note how once an evolutionary psychologist has the effect (clown phobia), almost any proposal can be suggested to explain it. This is why noted paleontologist Stephen Jay Gould (1997) called hindsight explanation nothing more than “speculation [and] guesswork in the cocktail party mode.”
Note: spiders were removed from this example because they are rarely poisonous and are far less dangerous than many other animals.

74. Critiquing Evolutionary Psychology
“You’re just taking current reality and constructing a way you could have predicted it.” This is hindsight reasoning and unscientific.
“You’re attributing too much to genes rather than the human ability to make choices about social behavior.”
Click to show two critiques and responses.
Instructor: You can ask students to explain why people all over the world like soccer based on an evolutionary psychology perspective. Students can invent great explanations…because our distant ancestors had to kick stones out of the way; because people who kicked lions really hard survived to spread their genes…etc.)
Response: yes, but there are predictions made about future behavior using this reasoning.
Response: yes, but our evolutionary past does not prevent our ability to act differently; “is” does not equal “ought.”

75. Evolution: Theory
Possible areas of consensus, with or without evolution:
The human mind and body seems almost “designed,” by evolution or other forces, to have certain traits and abilities.
Nurture may shape us, but we seem to start out with some sort of human nature.
Evolution is a scientific theory (NOT a “guess” and not a hypothesis, but something more): a coherent set of principles that fits very well with the accumulated evidence.
Parts of the evolutionary story may conflict with other stories of origins and change over time.
Is there room for overlap and agreement?
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