PSYCHOLOGY: Chapter 6 - The Body and Behavior Lecture Notes
* Bold print denotes an item not in the text.
6-1: The Nervous System: The Basic Structure
Runner's high: the natural “second wind” an athlete gets when endorphins are secreted and produce euphoria.
Endorphin: neurotransmitter that inhibits pain.
2 points on the nervous system:
1.) The nervous system is never at rest. There is always a job for it to do.
2.) Even when you are sleeping the nervous system is busy regulating your body functions.
4 things the nervous system controls:
2 parts of the nervous system:
1.) Central nervous system (CNS): Brain and spinal cord
2.) Peripheral nervous system (PNS): the nerves branching out from the spinal cord
3 points on the PNS:
1.) The nerves of the peripheral system conduct information from the bodily organs to the central nervous system and take information back to the organs.
2.) These nerves branch out from the spinal column.
3.) In size they are about as thick as a pencil (spinal nerves) to invisibly small (in the extremities).
Nerve fibers: These are what we call "nerves". These carry chemical-electrical messages from receptor cells to brain in 1/50 of a second.
* A-alpha nerve fibers: carry information related to proprioception (muscle sense).
* A-beta nerve fibers: carry information related to touch.
* A-delta nerve fibers: carry information related to pain and temperature.
* C-nerve fibers: carry information related to pain, temperature and itch.
Central nervous system: Powerhouse of the body made up of the brain and spinal cord.
Protection of the Nervous Systems:
4 types of protection:
Sheathing (myelin): A white, fatty substance that insulates and protects the axon for some neurons, and protects the brain and peripheral nerves.
Meninges: Series of 3 membranes that cover the brain and spinal cord.
- Dura mater, The outer layer of the meninges is called the dura mater or just the dura. The dura is a tough and thick fibrous
- Arachnoid: The middle layer is called the arachnoid - A clear membrane with fine strands (resembles a spider's) that surrounds a cap
of cerebrospinal fluid that covers the surface of the entire central nervous system. Below the arachnoid lies the
subarachnoid space. The cerebral arteries run through the subarachnoid space. (The subarachnoid space is the space into
which aneurysms of the cerebral vessels hemorrhage.)
- Pia mater: The innermost of the three membranes (meninges) that surround the brain and spinal cord of vertebrates is called the pia
mater (or just the pia). The pia mater lies immediately adjacent to the central nervous system, and the choroids plexus,
which secretes cerebrospinal fluid, is an extension of it.
Vertebrae: The adult vertebral (spinal) column consists of 26 bones that are grouped as follows: (** See diagram in study guide)
- cervical vertebrae: #7 in the neck; numbered C-1 to C-7. C-1 and C-2 do not move.
- thoracic vertebrae: #12 that articulate with the 12 pairs of ribs; numbered T-1 to T-12. Some rotation can
occur between the thoracic vertebrae, but their connection with the rib cage prevents much
- lumbar vertebrae: #5 of the lower back; numbered L-1 to L-5). These vertebrae are very robust in construction,
as they must support more weight than other vertebrae. They allow significant flexion and extension.
- sacrum: #1 which is actually a fusion of 5 sacral vertebrae. Fusion occurs from late teens to early 20's.
- coccyx or "tailbone": #1 which is a fusion of 4 coccygeal vertebrae
Intervertebral discs: located between adjacent vertebrae. These fibrocartilage discs form strong joints and absorb spinal compression shock.
Each disc allows slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.
* Disc degeneration: Over time, spinal discs dehydrate and become stiffer, causing the disc to be less able to adjust to compression.
While this is a natural aging process, in some individuals, as the disc degenerates it can become painful.
* Disc problems: Because of the way it is attached to the vertebra above and below it, a disc cannot “slip” as commonly thought. However,
trauma and injury to the spine can cause discs to bulge, be herniated or, even worse, rupture. This can be quite painful,
putting pressure on the spinal cord and nerve roots, interfering with function - and causing pain.
^ 3 common types:
1.) Disc Tear: The most common disc injury is a small crack or microtear in the tough, outer cartilage material of the disc
(called annular fibers). This allows the fluid to start leaking out, and the disc begins to wear thin.
2.) Bulging Disc: The soft jelly-like material in the middle of the disc pushes to one side, forward, or backward, and swelling
occurs. The nucleus is still contained within the tough outer fibers of the disc, but can still cause pressure and painful symptoms.
3.) Herniated Disc: The soft jelly-like material from the nucleus in the middle of the disc ruptures through the tough, outer fibers and extends to the outer edge or beyond
the normal limits of the disc.
Spinal cord: is about 45 cm (18 inches) long in men and 43 cm long in women. However, this is much shorter than the length of the bony spinal column. In fact, the spinal cord extends down to
only the last of the thoracic vertebrae. Therefore, nerves that branch from the spinal cord from the lumbar and sacral levels must run in the vertebral canal for some distance
before they exit the vertebral column.
* spinal nerves: 31 pairs of nerves that extend from the spinal cord outward to the body.
* cranial nerves: are 12 pairs of nerves that can be seen on the ventral (bottom) surface of the brain. Some of these nerves bring information from the sense organs to the brain;
other cranial nerves control muscles; other cranial nerves are connected to glands or internal organs.
* contains three-fourths of the body's neurons about (100 billion neurons).
* weighs about 3 pounds (human head weighs 8-10) About 2%-3% of the human body weight.
Skull: There are 8 bones that surround your brain. These 8 bones make up the cranium. Another 14 bones in the face make up the entire skull. There is a large opening, called the
foramen magnum, located in the back of the occipital bone. This is where the medulla ends and projects out of the skull. Smaller holes in the skull, called foramina, allow nerves and
blood vessels to enter and leave the cranium.
- sutures: the places in the skull where the bones come together fused together. These sutures are flexible in young children, but become fixed as you age.
Paralysis: the loss of power of voluntary movement in a muscle through injury or through disease, or the loss of sensation over a region of the body, of its nerve supply. Paralyzed means one cannot move due to
a severed spinal cord.
Neurons: the long, thin cells that constitute the structural and functional unit of nerve tissue along which messages travel to and from the brain.
- how messages are transmitted: Chemical electrical signals travel down the neurons much as flame travels along a firecracker fuse. Transmission between neurons occurs whenever the cells
are stimulated past a minimum point and emit a signal.
- # of times a neuron can “burn”: the neuron can fire (burn) over and over again, hundreds of times a minute.
- "all-or-none" principle: when a neuron fires, it does so at full strength. If a neuron is not stimulated past the minimum, or threshold, level, it does not fire at all.
* comparative example: In an engine, the sparkplug ignites the gaseous vapor in an engine cylinder. The piston (within the engine) does nothing until the sparkplug fires, causing the
vapor to explode.
- 3 basic parts: the cell body, dendrites, and axons.
* cell body: contains the nucleus and produces the energy needed to fuel neuron activity.
* dendrites: (receiver) are short, thin fibers that stick out from the cell body, that receive impulses, or messages, from other neurons and send them to the cell body.
* axons: (sender) is a long fiber that carries the impulses away from the cell body toward the dendrites of the next neuron.
^ size: can be very short or several feet in length.
- myelin sheath: A white, fatty substance that surrounds some neurons (neural tissue).
* 3 duties: Insulates and protects the axon, and speeds the transmission of impulses.
* Multiple Sclerosis: nervous system disease in which the myelin sheath is destroyed, and as a result, the behavior of the person is erratic and uncoordinated.
- axon terminals: branch out at the end of the axon; terminals are positioned opposite the dendrite of another neuron to receive impulses.
- Synapse: the gap that exists between individual nerve cells. It is a junction or connection between the neurons where the neuron transmits its impulses or message to another neuron.
* size: less that one millionth of an inch wide.
* contents: filled with fluid that transmits the chemicals from one neuron to another.
- Neurotransmitters: the chemicals released by neurons, which determine the rate at which other neurons fire. Neurotransmitters open chemical locks or excite the receptors.
* excite: making a neuron transmit.
* inhibition: stop a neuron from transmitting
* flow: in only one direction.
^ Norepinephrine: A substance, both a hormone and neurotransmitter, secreted by the adrenal medulla and the nerve endings of the sympathetic nervous system to cause blood vessel constriction
and increases in heart rate, blood pressure, and the sugar level of the blood. This neurotransmitter is also involved with memory and learning.
^ Endorphin: neurotransmitter that inhibits pain. (and
kind of creates a euphoria.
* supply level differences: The oversupply or undersupply of
certain neurotransmitters has
been linked to certain diseases.
^ Acetylcholine: a neurotransmitter involved in
movement and memory. A decrease
in this neurotransmitter is
associated with paralysis and
+ Alzheimer's disease: currently an irreversible,
incurable condition that destroys a
person’s ability to think, remember,
relate to others, and care for her or
^ Dopamine: neurotransmitter involved in learning,
emotional arousal, and movement. An
oversupply of this neurotransmitter is
associated with schizophrenia, and an
undersupply associated with Parkinson's
+ Schizophrenia: a group of severe psychotic
disorders characterized by
confused and disconnected
thoughts, emotions, behavior,
+ Parkinson's disease: A progressive nervous
disease occurring most often after the
age of 50, associated with the
destruction of brain cells that produce
dopamine, and characterized by
muscular tremor, slowing of movement,
partial facial paralysis, peculiarity of
gait and posture, and weakness.
^ Serotonin: a neurotransmitter involved in sleep,
depression, and memory. An undersupply
of norepinephrine and serotonin may
result in depression.
- neuron activity: each neuron is either "on" or "off" depending
on the neural activity around it.
* intensity: The intensity of activity in each neuron
depends on how many other neurons are acting
- Neural impulse destination: The actual destination of
nerve impulses produced by an excited neuron, as
they travel from one neuron to another, is limited by
what tract in the nervous system they are on.
* ascending tracts: carry sensory impulses to the brain.
* descending tracts: carry motor impulses from the brain.
- 3 types of neurons:
* afferent: also called sensory neurons they relay messages
from the sense organs (including eye, ear, nose,
and skin) to the brain.
* efferent: also called motor neurons, they send signals
from the brain to the glands and muscles.
* interneurons: carry impulses between neurons in the body.
2 types of actions: and a nervous system for each.
1.) voluntary: what you choose to do like lifting your hand
2.) involuntary: happen automatically like heartbeat and
Somatic Nervous System (SNS): the part of the peripheral nervous
system that controls voluntary
movement of skeletal muscles.
(Soma is Latin for body.)
Autonomic Nervous System (ANS): the part of the peripheral nervous
system that controls internal
It should be noted that the autonomic nervous system is always working. It is not ONLY active during "fight or flight" or "rest and digest" situations. Rather, the autonomic nervous system acts to maintain normal internal functions and works with the somatic nervous system. The ANS regulates:
in the skin (around hair follicles; smooth muscle)
around blood vessels (smooth muscle)
in the eye (the iris; smooth muscle)
in the stomach, intestines and bladder (smooth
of the heart (cardiac muscle)
- 3 parts of the ANS: sympathetic, parasympathetic and enteric
* Sympathetic nervous system: part of the ANS that
prepares the body for dealing with
emergencies or strenuous activity.
** This what kicks in your "fight or
^ 6 actions:
1.) It prepares the body for dealing with
emergencies or strenuous activity.
2.) It speeds up the heart to hasten the supply of
oxygen and nutrients to body tissues.
3.) It constricts some arteries and relaxes others
so that blood flows to the muscles, where it is
most needed in emergencies and strenuous
4.) It increases the blood pressure.
5.) It increases respiration.
6.) It suspends some activities (like digestion).
* Parasympathetic nervous system: works to conserve
energy and to enhance the body’s ability to
recover from strenuous activity.
- 4 actions:
1.) It works to conserve energy and to enhance the
body’s ability to recover from strenuous
2.) It reduces the heart rate.
3.) It reduces blood pressure.
4.) It works to bring the body back to its normal
* Enteric nervous system: regulates the normal activity
of the digestive system and
prepare it for whatever its
future may hold.
- "autopilot": All of this takes place automatically. Receptors
are constantly receiving messages that alert the
autonomic nervous system to carry out routine
- without one's ANS: We would have to consciously think about
doing even the most basic of activities…
and that would include breathing!
Early Greeks: were not really impressed with the brain.
- brain's function: was to cool the blood.
- heart's function: was the source of feelings and thoughts.
- Hippocrates: Ancient Greek philosopher who is considered to
be the “father of medicine”, believed
somewhat differently than most. He believed
diseases were caused by natural, not
supernatural (evil spirits) causes.
* effect of brain injuries: observed the effect of head
injuries on people’s thoughts and
actions and noted,
* quote: “[F]rom the brain, and from the brain only, arise
our pleasures, joys, laughter and jests, as well as
our sorrows, pains, griefs and tears. Through it, in
particular, we think, see, hear. . . . Eyes, ears,
tongue, hands and feet act in accordance with the
discernment [judgment] of the brain.”
^ meaning: There is more going on in the brain than
what most Greeks thought.
3 main parts of the brain: hindbrain, midbrain, and forebrain.
- hindbrain: a part of the brain located at the rear base of the
skull that is involved in the basic processes of life
such as sleeping, waking, coordinating body
movements, and regulating vital reflexes.
* 3 parts: cerebellum, medulla, and the pons.
^ cerebellum: a part of the brain that helps control
posture, balance, and voluntary
^ medulla: part of the brain that controls breathing,
heart rate, and a variety of reflexes.
+ contents: contains the respiratory, vasomotor
and cardiac centers, as well as
many mechanisms for controlling
reflex activities such as coughing,
gagging, swallowing and vomiting
^ pons: functions as a bridge between the spinal cord
and the brain. It is also involved in producing
chemicals the body needs for sleep.
- midbrain: serves as the nerve pathway of the cerebral
hemispheres and contains auditory and visual reflex
* action: integrates sensory information and relays it
- Brainstem: The lower extension of the brain where it connects
to the spinal cord.
* 5 neurological functions located in the brainstem:
3.) heart rate
4.) blood pressure
5.) arousal (being awake and alert)
** Notice these are functions necessary for survival.
* Cranial nerves: Most of the cranial nerves come from
* as a pathway: The brainstem is the pathway for all
fiber tracts passing up and down from
peripheral nerves and spinal cord to the
highest parts of the brain.
^ brain death: The brain can survive for up to about
4-6 minutes after the heart stops.
If CPR is started within six minutes
of cardiac arrest, the brain may
survive the lack of oxygen. After
about 6 minutes without CPR,
however, the brain begins to die.
Brain death is defined as the
irreversible loss of all functions of
It can be determined in several ways.
1.) No electrical activity in the brain; this is
determined by an EEG.
2.) No blood flow to the brain; this is
determined by blood flow studies.
3.) Absence of function of all parts of the
brain - as determined by clinical
- no movement
- no response to stimulation
- no breathing
- no brain reflexes.
4.) The patient can be given 1 mg of atropine
IV. In the patient with an intact brain,
atropine will dramatically increase the
patient's heart rate. In a brain-dead
patient, atropine will not influence heart
* Reticular activating system: serves to alert the rest of
the brain to incoming signals and is involved
in the sleep/wake cycle.
- Forebrain: the largest part of the brain that covers the brain’s
central core, consisting of left and right
hemispheres, which are connected by a wide band of
fibers, the corpus callosum.
Thalamus (3 actions):
1.) It integrates sensory input.
2.) It is a relay station for all the information that travels to and
from the cortex.
3.) All sensory information with the exception of smell enters
Hypothalamus (4 things it controls): It regulates the ANS.
1.) Controls functions such as hunger, thirst, and sexual behavior.
2.) Controls the body’s reactions to changes in temperature.
3.) Monitors the amount of hormones in the blood.
4.) Sends out messages to correct imbalances.
"new brain": refers to the cerebral cortex.
"old brain": Subcortex and the brain stem. We share this with
Examples to describe new and old brain: Peach and peach pit
Cerebrospinal fluid: The entire surface of central nervous system
is bathed by a clear, colorless fluid called
cerebrospinal fluid (CSF). The CSF is
contained within a system of fluid-filled
cavities called ventricles.
- 4 functions
1.) Protection: the CSF protects the brain from damage
by "buffering" the brain. In other words,
the CSF acts to cushion a blow to the
head and lessen the impact.
2.) Buoyancy: since the brain is immersed in fluid, the
net weight of the brain is reduced from
about 1,500 gm to about 50 gm.
Therefore, pressure at the base of the
brain is reduced.
3.) Excretion of waste products: the one-way flow from
the CSF to the blood takes potentially
harmful metabolites, drugs and other
substances away from the brain.
4.) Endocrine medium for the brain: the CSF serves to
transport hormones to other areas of the
brain. Hormones released into the CSF can
be carried to remote sites of the brain
where they may have some action.
Cerebral cortex: gives you the ability to learn and store complex and
abstract information, and to project your thinking
into the future. All of the functions of the
cerebral cortex are not fully understood.
- size: about 80% of the brain's weight.
Limbic system: is composed of a number of different structures in
the brain that regulate our emotions and motivations.
- 4 parts: hypothalamus, amygdala, thalamus, and hippocampus.
Amygdala: controls violent emotions such as rage and fear.
Hippocampus: is important in the formation of memories.
- if damaged: it would be difficult to form new memories.
Cerebrum: is the site of your conscious thinking processes, yet it is
less than one-fourth inch thick.
Hemispheres of the brain: You have two hemispheres or sides to your
brain. Each hemisphere contains half of
each of the four lobes of the brain.
- control: The left hemisphere controls the right side of your
body, and the right hemisphere controls the left side
of your body.
Corpus callosum: the band of fibers that connect the cerebral
hemispheres. It carries messages to and from the
Lobes: the different regions into which the cerebral cortex is
- Occipital: where visual signals are processed.
* controls: everything optic.
* if damaged: can cause visual problems. A blow to the back
of the head can cause serious damage to the
- Parietal: is concerned with information from the senses from all
over the body (body sensation). It is concerned with
sense of touch, differentiation (identification) of size,
shapes, and colors, spatial perception, and visual
- Temporal: is concerned with hearing, memory, understanding
language (receptive language), organization,
sequencing, emotion, and speaking.
- Frontal: controls personality, planning for future
action, emotional control, attention, concentration,
creativity, initiation, problem solving, judgment,
self-monitoring, motor planning, organization,
mental flexibility, speaking (expressive language),
impulse control (inhibition of behavior), awareness
of abilities and limitations, and the ability to
censor thoughts and ideas.
* This is the lobe that sustains the most injuries.
3 ways we find out what parts of the brain control:
- accidental or purposeful damage an area of the brain
- use of chemical or electrical stimulation to various areas
Amount of brain tissue allotments: The number of touch sensors in a
body part determines its sensitivity, and, along with
the complexity of the part’s movement, governs the
amount of brain tissue associated with the part.
- example: The touch and movement of the hands involve more
brain area than the more limited calves.
Can the brain feel pain? No, because there are no receptor cells
in it. You are even kept "awake" for
some brain surgeries.
Somatosensory cortex: receives information from the touch sensors.
Motor cortex: sends information to control body movement.
- division: is also divided according to need. The more
sophisticated the movements (such as those used in
speaking), the bigger the brain area involved in their
Association areas: mediate between the other areas.
- 2 actions:
1.) Does most of the synthesizing of information.
2.) Turns sensory input into meaningful information.
Right and left hemispheres: most information about properties
of the left and right hemispheres is
- popular ideas: have oversimplified the properties of the two
* reality: In reality, the left and right sides complement and
help each other.
- as mirror images: Each of the four lobes is present in both
- function of corpus callosum: carries messages back and forth
between the two hemispheres to jointly control
- how connected: Each hemisphere is connected to one-half of
the body in a crisscrossed fashion.
Left hemisphere (5 points):
1.) Controls the movements of the right side of the body.
2.) For most people, the left side of the brain is where speech is
3.) mathematical ability
Right hemisphere (9 points):
1.) Controls the left side of the body.
2.) more adept at visual ability
3.) spatial relations
4.) Perceptual tasks are mostly processed here.
5.) Recognizing patterns
Dyslexia: is a common reading disorder that is strongly linked to
differences in brain function. It can be perceptual in
nature or a problem with processing the information.
- Early labels: Poor readers were labeled as lazy or slow.
- Today: we recognize that dyslexics’ brains function
differently. Several recent studies indicate that
dyslexics use more of their brain area to complete
simple language tasks.
- Imaging techniques: PET scans and MRIs assist researchers
in explaining how dyslexics’ brains
- Genetics: Researchers are also exploring a genetic link that
may indicate that dyslexia is largely an inherited
L/R Handedness v L/R Brained: Not the same thing.
Right-handed children and brain development: Right-handed
children are genetically predisposed to develop
verbal left hemispheres, but the actual
specialization occurs over the years.
In brain injury: This is why little kids that sustain a head injury
can get better faster, and progress more, than adults
in the same situation can.
- For example speech: If a child suffers damage to
the left hemisphere, the right will take over the
function of speech. The child may learn more slowly
than other kids, but he or she will learn to speak
again. However, almost all adults who suffer damage
to the left hemisphere have extreme difficulty
speaking, if they can speak at all.
The clear difference between the hemispheres: applies primarily
to right-handed people.
- Right-handedness: Righties have significant differences
between the hemispheres - their
left is much more developed.
- Left-handedness: Lefties have less of a dramatic
difference between the hemispheres
because they have to live in a
- % Of right-handed people worldwide: 90%
- Herron (1976): said that left-handed people are truly
discriminated against by having to live in a
* examples of left handed discrimination: doorknobs,
manual transmissions, pencil sharpeners,
light switches, spiral notebooks, student
Effect of a Stroke: Thus a stroke that causes damage to the
right hemisphere will result in numbness or
paralysis on the left side of the body.
- In right handed people: the left hemisphere usually controls
language and the right is involved in
spatial tasks, so if he "stroked" on
the left there would be numerous
Epilepsy: Since the brain uses electrochemical energy, any disruption
of the electrical processes in the brain will cause abnormal
functioning. In this disease, neurons in the cerebral
hemispheres misfire and create abnormal electrical
People with this disease have seizures that happen
repeatedly. It is a bit like an electrical brainstorm.
The seizure prevents the brain from interpreting and
processing incoming sensory signals (like visual,
somatosensory and auditory information), and controlling
muscles. That is why affected people may fall down and
This is a fairly common neurological disorder, and occurs in
about 1 in every 100-200 people.
- 3 ways epileptics have been viewed in history:
1.) Believed to be possessed by evil spirits
2.) Presumed to be insane
3.) Assumed to be unintelligent.
* discrimination: They were discrimination because of
their ailment and the way it affects
their behavior; said to be unfit for
Split-brain surgeries: surgery to separate the brain hemispheres
originally used to lessen the number and severity of the
epileptic seizures. The person has two brains that operate
independently of each other. Since the corpus callosum is
severed, there no longer is any communication between the
- Kalat, 2001: found that separating the brain hemispheres
lessens the number and severity of the seizures.
- how brain works after a surgery: The person has two brains
that operate independently of each other.
- communication between hemispheres: Since the corpus
callosum is severed, there no longer is any
communication between the hemispheres…
and that means that the seizure cannot
cross over either.
Harriet Lees: an epileptic patient who's only hope was a split-brain
- early life: For most of her life Lees’s seizures were mild and
could be controlled with drugs.
- @25: seizures began to get worse.
- @30: having as many as a dozen violent seizures a day.
- reasoning for a split-brain operation: No other choice. She
had little quality of life as she was.
- 2 results for Lees:
1.) Reduced the severity of seizures
2.) She had fewer seizures
- effects of the surgery: Despite the fact that patients who had
this operation now had two functionally
separate brains, they seemed
remarkably normal. (See page 164-165)
Individuals who have had split-brain
operations remained practically
unchanged in intelligence, personality,
* tactile stimulation: touch
Brain mapping: is the task of identifying the functions of different
regions of the brain. It is one of the largest areas of
study in psychology and medicine right now.
- physiological psychologists: same as below
- psychobiologists: scientists responsible for the mapping of the
brain’s fissures and inner recesses, and
supplying others with fascinating information
about the role of the brain in behavior.
4 methods used to study the brain: recording, stimulating, lesioning,
Recording: ways to obtain electrical impressions of brain waves
and study them.
- electrodes: are wires that can be inserted into the brain to
record electrical activity in the brain.
* process: By inserting electrodes in the brain, or onto the
scalp, it is possible to detect the minute
electrical changes that occur when neurons fire.
The wires are connected to electronic equipment
that amplifies the tiny voltages produced by the
firing neurons. Even single neurons can be
- Electroencephalograph (EEG): a machine used to record the
electrical activity of large
portions of the brain.
- brain activity: the electrical activity of the brain rises and falls
rhythmically. These rhythms, or brain activity,
occur because the neurons in the brain tend to
increase or decrease their amount of activity in
unison. Their intensity depends on the state of
consciousness the individual is in during the
* 3 states of consciousness examined: awake, drowsy, or
Stimulation: the use of electricity or chemical to set off the firing of
neurons in the brain.
- 2 methods: electric and chemicals.
- 2 "centers" in the brain: punishment and pleasure centers.
One is painful and the other delivers feelings of
euphoria -- like narcotics-- so the person likes the
feelings he/she gets when this area is stimulated.
The “pleasure center” is what is being stimulated
when we are engaging in activities we enjoy.
- Olds and Olds (1965): They implanted electrodes in the
brains of rats. The rat was then placed into a
cage where he could press a lever, which would
deliver a mild electrical current. When the
electrode was placed in the "pain" center, the rat
would not touch the lever even if it meant not
eating. But if the electrode was placed in the
"pleasure" center, he would press the lever several
thousand times an hour… and be higher than a kite.
- Wilder Penfield: brain surgeon who stimulated the brains of his
epileptic patients during surgery to determine
what functions the various parts of the brain
He is considered a major pioneer in the
area of brain mapping.
* use: to localize the malfunctioning part for which surgery
* temporal lobe: When he applied a mild electrical
current to points on the
temporal lobe of the brain, he
could trigger whole memory
* Penfield & Rasmussen, 1950: Did a similar study to
Penfield's. In it one woman heard a
familiar song so clearly that she thought
a record was being played in the
- 7 uses of stimulation:
1.) Used with terminal cancer patients to relieve them of
intolerable pain without using drugs.
* Delgado, 1969: Found that a current delivered
through electrodes implanted in certain areas
of the brain may provide a sudden temporary
2.) Some psychiatrists have experimented with similar
methods to control violent emotional behavior in
otherwise uncontrollable patients.
3.) Used in Parkinson's patients to control tremors.
4.) Successfully used to treat essential tremor.
* Essential Tremor: Essential tremor is a
movement disorder characterized by
the involuntary shaking of hands and
other body parts that is evoked by
intentional movements. It is unknown
why essential tremors occur, however
it is estimated to be as common as one
person in 20, and it is the most
common type of tremor and the most
commonly observed movement disorder.
Voluntary movements such as holding a
cup, fork, or pen make the tremor
worse. Signs and symptoms may
increase as your activity increases.
5.) Used to treat Dystonia.
* Dystonia: a group of complex muscle disorders
that involve involuntary twisting,
repetitive movements that cause
abnormal, sometimes painful
^ most common example: Writer's cramp
6.) Experimental usage to treat chronic pain.
7.) Beginning to be used experimentally to treat depression
that is resistant to all other forms of treatment.
Lesions: a damaged area of brain, either done on purpose or by
- why: If the animal behaves differently after the operation,
they assume that the destroyed brain area is involved with
that type of behavior.
- Kulver & Bucy, 1937: in one classic lesion study, two
researchers removed a certain area of the
temporal lobe from rhesus monkeys. Normally,
these animals are fearful, aggressive, and vicious,
but after the operation, they became less fearful
and at the same time less violent.
* implication: The implication was that this area of the
brain controlled aggression. The relations
revealed by this type of research are far
more subtle and complex than people first
Psychosurgery: brain surgery aimed at changing a person's
thoughts or actions by destroying a part of the
brain. This is rarely used.
- Prefrontal lobotomy: a surgical technique where a part of
the frontal lobes is destroyed in an
effort to change behavior or cure
"craziness". About 50,000 of these
were done between 1935 and 1955.
This was one of the only true
"treatments" science had discovered
for treating mental illnesses.
- Side effects: patients had trouble dealing with new
information, and problems in pursuing goals
(concentration), easily distracted.
- Valenstein Quote: "There are certainly no grounds for
either position that all psychosurgery
necessarily reduces people to a
'vegetable status' or that it has a
high probability of producing miraculous
cures. The truth, even if somewhat
wishy-washy, lies in between the
extreme positions. There is little doubt,
however, that many abuses existed."
- Effect of introduction of drug therapies: In the 1950's,
new drugs were introduced that altered the
chemical balances in the brain. These have
helped people dramatically.
-"New" surgeries: Surgeons now can destroy a small area
of the brain to control some behaviors. A
cingulotomy is one example.
- National Association of Mental Health's stand: It argues
that “psychosurgery should only be used as a
- Current # of psychosurgeries per year: less than 100
- Commission for the Protection of Human Subjects of
Biomedical and Behavioral Research: An 11 member
Congressionally appointed committee who studied
the use of psychosurgery and determined that
they did not approve of the older technique of
frontal lobotomy, but some of the newer
operations seem to work well.
- Cingulotomy: the destruction of a major subcortical
structure, which seems to be very successful
in dealing with chronic pain and severe
depression. The nerve fibers destroyed are
part of a pathway important in emotions and
motivation. The surgery appears to eliminate
the discomfort and suffering the patient
feels, but does not interfere with other
mental faculties such as thinking and memory.
(It has also been experimentally used to treat
Electroconvulsive therapy (ECT): Better know as "shock therapy".
It is only used to treat severe depression when meds
and other psychotherapy treatments fail. It sends an
electrical current through the brain, which changes the
brain chemistry. Approximately 110,000 Americans have
this treatment per year.
Although shock therapy has been performed for
decades, researchers still don't know precisely how it
works to combat depression.
- The major theories:
1.) Neurotransmitter theory: Shock works like anti-
depressant medication, changing the way brain
receptors receive important mood-related
chemicals, such as serotonin and dopamine and
2.) Anti-convulsant theory: Shock-induced seizures teach
the brain to resist seizures. This effort to
inhibit seizures dampens abnormally active
brain circuits, stabilizing mood.
3.) Neuroendocrine theory: The seizure causes the
hypothalamus, part of the brain that regulates
water balance and body temperature, to
release chemicals that cause changes
throughout the body. The seizure may release
a neuropeptide that regulates mood.
4.) Brain damage theory: Shock damages the brain, causing
memory loss and disorientation that creates a
temporary illusion that problems are gone.
Tissue implants: There has been research in taking brain tissue
from donors (and aborted fetuses) and implanting
it in a patient's brain. One day soon these could
be used to treat Parkinson's disease.
Parkinson's Disease is a progressive disorder of the central
nervous system. It is not a mental illness and
is not contagious or fatal.
- treatment: It has not yet been possible to develop a cure
but most patients respond to medication and
physical therapy. Modern medication can help
most patients to enjoy an active and full life
span. A wide variety of drugs and therapies
can help to combat almost any problem that
- symptoms: There are five classic symptoms and signs,
although their presence and intensity varies
widely from patient to patient:-
3.) Bradykinesia - Slowed ability to
start and continue
movements, and impaired
ability to adjust the body's
4.) Gait (walking) disorder
5.) Loss of Balance
- Dr. James Parkinson: was a general practitioner in
palsy". His report was published in
1817 and contained the clinical
- rate: The condition occurs at the rate of 228 per 100,000
-age of onset: usually begins between the ages of 50 and 65.
* most affected age group: It is much more prevalent in
the 60 to 69 age group but is sometimes
seen in patients under 40 years of age,
with an incidence of ten per 100,000.
- cause: Parkinson's disease occurs when certain nerve cells,
or neurons (in an area of the brain known as the
substantia nigra) die or become impaired. Normally,
these neurons produce an important brain chemical
known as dopamine.
* Dopamine: is a neurotranmitter responsible
for transmitting signals between
the substantia nigra and the next
"relay station" of the brain, the
corpus striatum, to produce
smooth, purposeful muscle activity.
* Loss of dopamine: causes the nerve cells of
the striatum to fire out of control,
leaving patients unable to direct or
control their movements in a normal
manner. Studies have shown that
Parkinson's patients have a loss of 80
percent or more of dopamine-
producing cells in the substantia nigra.
The cause of this cell death or
impairment is not known.
- cure: It has not yet been possible to find a cure but most
patients respond to medication and physical therapy,
which can greatly alleviate the symptoms.
- Modern medication: can help most patients to lead an
active, full life span. A wide variety of
drugs and therapies are available to
combat almost any problem that
* goal of medication: The goal is to restore artificially
the balance of dopamine, which is
lacking in the brain. A combination
of drugs can often improve the
lifestyle of patients and keep them
active both mentally and physically.
- Therapies: A special exercise program Physical therapy may
be specified by the doctor to increase muscle
mass and coordination. Speech therapy assists in
improving speech and swallowing. Occupational
therapy can improve manual dexterity and
activities of everyday life.
- Research is proceeding vigorously. Understanding of the
complex processes that occur in the brain is
improving rapidly. Many new treatments are
becoming available to alleviate symptoms and
improve the quality of life for patients.
Use of accidents in studying the brain: Psychologists can learn from
the tragedies when some people suffer accidents.
These accidents may involve the brain. Psychologists try
to draw a connection between the damaged parts of the
brain and a person’s behavior.
Phineas Gage: In 1848, he was a 25 year-old railroad crew
of explosives into the earth, when the charge
accidentally exploded. An iron tamping rod that he
was using was propelled like a rocket and hit him in
the head. The rod was 3 feet 7 inches long and
weighed 13 pounds! It hit Phineas in the left
cheek, went straight
through his skull and brain
and came out the top of
his head. (page 167)
- aftermath: They cleaned out the terrible wound, and all
the time Phineas never lost consciousness. Over
the next couple of weeks, he bled severely,
became quite confused, and lost the sight in his
left eye. However, he lived for 13 more years,
which astounded all those who treated him,
although he never lived a "profitable life", he
did manage to hold a job for a few years. At
one time he was part of the "freak show" of a
- Effects: Surprisingly enough he was not killed and only
suffered minimal damage. His personality did
change dramatically - before the accident he was
a mature, trustworthy and dependable, and after
he was childish, and emotionally volatile, and anti-
- Damasio & Damasio, 1994: psychologists who examined Gage’s
skull (his family had donated it to
newest methods available. They
reported that the tamping iron had
caused damage to parts of the
frontal cortex. They found that
damage to the frontal lobes
prevents censoring of thoughts and
- Frontal lobes control: personality, creativity, planning for
future action, emotional control, attention,
concentration, initiation, problem-solving,
judgment, self-monitoring, motor planning,
organization, mental flexibility, speaking
(expressive language), impulse control (inhibition of
behavior), awareness of abilities and limitations,
and the ability to censor thoughts and ideas.
Paul Broca: French pathologist, neurosurgeon, and anthropologist,
(1824-1880) made important contributions to anatomy,
physiology and anthropology, and he was the founder of
modern brain surgery.
He had a young patient who could only respond with hand
gestures and the word “tan”… and he wanted to know why
this was so.
- theory: Broca theorized that a part of the brain on the left
side was destroyed, limiting the young man’s
communication processes… and he was right.
- Broca's Area: the left side of the cortex, which is involved with
the production of speech.
6 types of brain imaging:
1.) Computer axial tomography (CT scan)
2.) Brain Electrical Activity Mapping (BEAM).
3.) Event-Related Potentials (ERP)
4.) Positron emission tomography (PET scan)
5.) Magnetic resonance imaging (MRI)
6.) Functional magnetic resonance imaging (fMRI)
Computer axial tomography (CT scan): an imaging technique in which
low levels of x rays are passed through the brain and a
computer measures the amount of radiation absorbed
by the brain cells and produces a relatively good image
of the brain.
- 2 uses: to pinpoint injuries and other problems in brain
- process: During a CAT scan, a moving ring passes X-ray
beams around and through a subject’s head.
Radiation is absorbed in different amounts
depending on the density of the brain tissue.
Computers measure the amount of radiation
absorbed and transform this information into a
three-dimensional view of the brain.
Brain Electrical Activity Mapping (BEAM): provides computer-
generated maps of brain activity, with different colors
indicating different levels of activity.
Event-Related Potentials (ERP): measure changes in patterns of
brain activity in response to specific external stimuli.
Positron emission tomography (PET scan): an imaging technique used
to see which areas of the brain are being activated
while performing tasks. Shows the glucose
consumption of the neurons.
- glucose: Blood sugar
- process: It involves injecting a slightly radioactive
solution into the blood and then measuring the
amount of radiation absorbed by blood cells.
Active neurons absorb more radioactive solution
than nonactive ones.
- 2 uses:
1.) Researchers use the PET scan to see which areas
are being activated while performing a task
2.) PET scans show activity in different areas of the
brain when a person is thinking, speaking, and
looking at objects.
Magnetic resonance imaging (MRI): an imaging technique that passes
non-harmful frequencies through the brain;
a computer measures the interaction with
brain cells and transforms this interaction
into an incredibly detailed image of the
brain (or body).
- as a combination: it combines the features of both CAT
and PET scans.
- 3 uses:
1.) to study the structure of the brain
2.) to identify tumors
3.) to find types of brain damage.
Functional magnetic resonance imaging (fMRI): used to directly
observe both the functions of different
structures of the brain and which structures
participate in specific functions. This provides
high resolution reports of neural activity based on
signals that are determined by blood oxygen level.
It actually detects an increase in blood flow to the
active structure of the brain.
- 3 uses:
1.) observe functions of structures
2.) learn which structures participate in specific
3.) detects an increase in blood flow to the
active structure of the brain.
- how it differs from a MRI: the fMRI does not require
passing radio frequencies
through the brain.
- 2 major causes of brain damage: Strokes and head injury
- Brain death: occurs within 4-6 minutes.
- Neurons begin to die within 2 minutes.
- 2 reasons neurons die: lack of oxygen and over stimulation.
- Effect of Magnesium: blocks transmission is synapses. IF
injected into brain it slows down the
degenerative process and saves some
- Effect of Insulin: slows activity down, and lowers body
temperature. This can delay, or prevent
damage from stroke.
*** Exception to the rule - Hypothermia: a state of
coldness, which causes everything to
slowing down. A brain can survive longer
at a low temperature because it is using
less oxygen. The younger the patient, the
better his/her chance of survival. There
have been cases of kids having little to
no brain damage from being immersed in
ice cold water for up to 20 or 30
"Adrenaline rush": comes from a hormone secreted by the endocrine system called adrenaline or epinephrine.
Adrenaline/Epinephrine: hormone that is a natural stimulant. It
activates the sympathetic nervous system.
It helps a person generate extra energy to
handle a difficult situation.
- how it works: The adrenal hormone declares an emergency
situation to the body, requiring the body to
become very active.
2 communication systems in the body: Nervous system and the
Endocrine System: a chemical communication system, using hormones,
by which messages are sent through the
- hormones: chemical substances that carry messages through
the body in blood.
* # of: Scientists have discovered more than 30
different hormones in the human body.
* 3 basic things hormones do:
1.) regulate cell metabolism
2.) control growth
3.) control reproduction
- 6 points on the endocrine system:
1.) Hormones circulate throughout the bloodstream but are
properly received only at a specific site: the particular
organ of the body that they influence.
* endocrine glands: release hormones directly into the
bloodstream; also called ductless glands.
* exocrine glands: release their contents through small
holes, or ducts, onto the surface of
the body, or into the inside of the
^ examples: tear ducts, salivary glands, sweat
2.) Hormones have various effects on your behavior. They
affect the growth of bodily structures such as muscles
and bones, so they affect what you can do physically.
3.) Hormones affect your metabolic processes; that is, they
can affect how much energy you have to perform actions.
4.) Some hormonal effects take place before you are born.
Essentially all the physical differences between boys and
girls are caused by a hormone called testosterone.
* testosterone: hormone that helps decide the sex of a
fetus, and is important for the growth
of muscle and bone along with the
growth of male sex characteristics.
5.) Certain other hormones are secreted during stressful
situations to prepare the body for action.
6.) Hormones also act in the brain to directly influence your
moods and drives.
- 10 endocrine glands and basic effects (pg 172)
1.) Hypothalamus: controls the pituitary gland, among other
2.) Pineal gland: may affect sleep cycle; inhibits
3.) Pituitary gland: regulates growth and water and salt
4.) Thyroid gland: controls the metabolic rate.
5.) Adrenal cortex: regulates carbohydrate and salt
6.) Adrenal medulla: prepares the body for action.
7.) Pancreas: regulates sugar metabolism.
8.) Ovaries (female): affects physical and sexual
9.) Testes (male): affects physical and sexual development.
10.) Thymus gland: involved in immunity
- pituitary gland: the center of control of the endocrine system
that secretes a large number of hormones.
* as the "master gland": it runs most of the endocrine
1.) monitors the amount of hormones in the blood
2.) sends out messages to correct imbalances.
3.) Controls functions such as hunger, thirst, sexual
behavior, and the body’s reactions to changes in
- Hormones: chemical substances that carry messages through
the body in blood.
* 5 actions:
1.) They carry messages to organs involved in regulating
and storing nutrients so that despite changes in
conditions outside the body, cell metabolism can
continue on an even course.
2.) They also control growth
3.) They control reproduction.
4.) They control ovulation
5.) They control lactation (milk production) in females.
- Thyroid gland: endocrine gland that controls the metabolic rate
and produces the hormone thyroxine.
* thyroxine: stimulates certain chemical reactions that are
important for all tissues of the body.
* Hypothyroidism: a disease caused by too little thyroxine,
which makes people feel lazy and
* Hyperthyroidism: a disease caused by too much thyroxine,
which causes people to lose weight and
sleep and to be overactive.
- Adrenal glands: become active when a person is angry or
* "fight or flight" response: activation of your
sympathetic nervous system.
* 6 actions:
1.) They become active when a person is angry or
2.) They release epinephrine and norepinephrine into
3.) These secretions cause the heartbeat and breathing
4.) They can heighten emotions, such as fear and
5.) These secretions and other changes help a person
generate the extra energy he or she needs to
handle a difficult situation.
6.) The adrenal glands also secrete cortical steroids.
* cortical steroids: help muscles develop and
cause the liver to release
stored sugar when the body
requires extra energy for
- sex glands: 2 types - male and female
1.) testes: produce sperm and testosterone which affects
physical and sexual development.
^ testosterone: male sex hormone
* Low levels of testosterone are also found in
+ importance: in the physical development of
males, especially in the prenatal
period and in adolescence.
+ during the prenatal period: it helps decide the
sex of a fetus.
+ during adolescence: is important for the growth
of muscle and bone along
with the growth of male sex
2.) ovaries: produce eggs and the female hormones estrogen
^ 2 hormones secreted
+ estrogen: a general term for female steroid sex
hormones which are secreted by the
ovary and responsible for typical
female sexual characteristics.
+ progesterone: a steroid hormone produced in the
ovary; prepares and maintains the
uterus for pregnancy.
^ 3 points:
1.) These hormones also regulate the reproductive
cycle of females.
2.) The levels of estrogen and progesterone vary
throughout the menstrual cycle.
3.) These variances can cause premenstrual
syndrome (PMS) in some women.
+ PMS: premenstrual syndrome
- PMS includes symptoms such as
fatigue, irritability, and
Hormones vs. neurotransmitters
- how they are similar: Both effect the nervous system.
- norepinephrine: A substance, both a hormone and
neurotransmitter, secreted by the adrenal medulla and the
nerve endings of the sympathetic nervous system to cause
blood vessel constriction and increases in heart rate, blood
pressure, and the sugar level of the blood. This
neurotransmitter is also involved with memory and learning.
- difference between: When a chemical is used as a
neurotransmitter, it is released right beside the cell
that it is to excite or inhibit. When a chemical is used as
a hormone, it is released into the blood, which diffuses
it throughout the body.
* example: Norepinephrine is a hormone when it is secreted
into the blood by the adrenal glands.
Norepinephrine is a neurotransmitter, though,
when it is released by the sympathetic motor
neurons of the peripheral nervous system.
- Snyder, 1985: Found that hormones and neurotransmitters
appear to have a common evolutionary origin.
As multicellular organisms evolved, the system
of communication among cells coordinated their
actions so that all the cells of the organism
could act as a unit. As organisms grew more
complex, this communication system began to
split into two more specialized communication
* 2 systems:
One, the nervous system, developed to send rapid and
specific messages, while the other, involving the
circulatory system, developed to send slow and
In this second system, the chemical messengers
evolved into hormones.
- speed of transmission: Neural (chemical/electrical) messages
can be measured in thousandths of a
second (about 250 mph), hormonal
(chemical) messages may take minutes
to reach their destination and weeks or
months to have their total effect.
role of genes: Genes establish what you could be.
role of environment: Environment defines the final product.
Heredity vs. Environment argument/debate: People often argue about
whether human behavior is instinctive (due to heredity) or
learned (due to environment).
- heredity: is the genetic transmission of characteristics from
parents to their offspring.
- reason for argument/debate: Many people assume that
something learned can probably be changed, whereas
something inborn will be difficult or impossible to
change. The issue is not that simple, however.
- interaction of heredity and environment: Inherited factors and
environmental conditions always act together in
Nature vs. Nurture: aka heredity vs environment.
- Nature: refers to the characteristics that a person inherits;
his or her biological makeup.
- Nurture: refers to environmental factors, such as family,
culture, education, and individual experiences.
Sir Francis Galton: became one of the first to preach the importance
of nature in the modern era.
- Heredity Genius: a book in which he analyzed the families of
over 1,000 eminent politicians, religious
leaders, artists, and scholars.
* date: 1869
- Method of study: He read biographies.
- His conclusion: He found that success ran in families and
concluded that heredity was the cause.
John Watson: the founder of behaviorism, who emphasized the
importance of the environment.
- Quote: “Give me a dozen healthy infants, well-formed,
and my own specified world to bring them up in and I’ll
guarantee to take any one at random and train him to
become any type of specialist I might select—a doctor,
lawyer, artist, merchant-chief, and, yes, even
beggarman and thief, regardless of his talents,
penchants, tendencies, abilities, vocations, and race of
- Meaning: Environment is the only factor that is important.
Genetics play only a small role. Watson’s idea is
Genes: the basic units of heredity.
- 3 points:
1.) They are reproduced and passed along from parent to
2.) All the effects that genes have on behavior occur
through their role in building and modifying the physical
structures of the body.
3.) Those structures must interact with their environment
to produce behavior.
3 areas of genetic influence on human traits:
1.) Cognitive abilities (like IQ)
2.) Mental illness
Charles Darwin: English biologist who in 1859 published his theory of evolution. (in The Origin of Species)
- 2 main ideas:
1.) All animal species are related to one another
2.) The structure of bodies and behavior patterns can
be distinguished and compared
His theory does not mean that humans do not possess unique qualities. It does, however, make it possible to think of humans as members of a particularly complex, interesting species rather than as totally different from other animals.
Ethology: the study of animal behavior in its natural environment
- 2 things Ethologists study: They study how the behavior
patterns have evolved and changed and how they are
expressed in humans.
Species-specific behavior: behaviors of characteristics of a
particular animal species
Stereotyped behaviors: patterns of responses that cannot change
readily in response to changes in the
- Effect of environment: These will work well only if the
environment stays as it was when the behavior
Fixed action patterns: inflexible patterns of response. The animal
can only act one way. (Also called
Instinct: a behavior that is inborn rather than learned.
** People often misuse the word instinct to refer to behaviors that have become automatic over a long period of practice.
Ethologists have found that animals are born with special sensitivities to certain cue in the environment, as well as with special ways of behaving.
Sign stimuli: cues in environment, which cause animals to respond
in certain ways.
- In humans: although instincts are less common and less
powerful in humans, there is evidence that some
stereotyped behaviors exist.
- Sign stimuli examples in humans: the parental instinct, and
the survival instinct.
Konrad Lorenz: Psychologist who did studies on learning and
instincts. He said that all humans possess the “parental instinct” - A human baby (or any baby animal) can cause an adult human to feel the need to take care of it.
Human ethology: study of human behavior as it naturally occurs.
Sociobiology: the study of the biological basis for social behavior.
- 3 other areas of study:
- Edward Wilson: Harvard zoologist published a book where
he defined the term “sociobiology”.
* 2 ideas:
1.) There are certain traits we share with animals. 2.) These behaviors are passed along genetically.
- 3 ideas of sociobiologists:
1.) They regard their discipline as the last phase of the
revolution begun by Charles Darwin.
* Natural selection: nature’s goal is individual
survival and reproduction.
Even though there are lots of examples where this
may not be the case.
* Soldier ants: will fight to the death to save the
group from invaders.
* Birds: will call out to each other if there is a
predator nearby, even though the warning
alerts the predator to the location of that
* Dolphins: have been known to band together to
protect can injured companion on the
surface of the water where it can
* Humans: Parents rescuing kids, EMS risking their
lives to save some one else, a soldier
sacrificing his/her life to save a platoon.
2.) Sociobiologists fit all these acts of self-sacrifice
into nature’s economy. They explain that Altruism:
(the unselfish concern for the welfare of others)
itself favors genetic gain: the individual risks itself,
but the results of this behavior is that other
individuals who share its genes survive.
3.) Sociobiology seeks to explain social behavior, even
aggression, in terms of genetic advantage.
3 points on the effect of heredity on social behavior:
1.) Human kind is flexible.
2.) Genetic inclinations don't have to be always obeyed and
sometimes shouldn't be.
3.) The evolution takes place so slowly that we may still be
inheriting behavior patterns that were adaptive in
prehistoric times, but are no longer useful today.
Major contribution of sociobiology: has been to remind us that genes do count, but that human beings have the capacity to learn a wide range of behaviors and unlearn those that cease to be adaptive.
Back to heredity vs environment-- Now the problem is that most children are raised by their biological parents and in the same environment. If this is the case, how can one tell which factor is most at work? In order to truly get a clear picture of the importance of each, we need to study individuals who share the same genetic make up, AND are not raised in the same environment. Solution: Study twins.
Twin studies: best way to look for genetic and environmental links.
Identical twins: develop from a single fertilized egg (thus, they are
called monozygotic) and share the same genes.
Fraternal twins: develop from two fertilized eggs (thus, dizygotic),
and their genes are not more similar than those of
brothers or sisters.
Mirror image twins: are identical twins that result when a fertilized
egg splits later in the embryonic stage than usual,
typically from day 9 to 12. They tend to exhibit
characteristics with reversed asymmetry (e.g.,
one twin is left-handed and the other is right-
handed). If this split happens much later than
this, then the twins can be co-joined.
Twins growing up in the same house share the same general environment, but identical twins also share the same genes.
So, if identical twins who grow up together prove to be more alike on a specific trait than fraternal twins do, it probably means that genes are important for that trait.
But what if identical twins are adopted into separate families? Then could we possibly tell if traits are genetic or environmental.
Thomas Bouchard: Psychology researcher at the University of Minnesota who studies twins. He is considered of the leading authorities on twins. He has performed numerous studies comparing twins that were separated at birth and placed in adoptive homes to see the links between heredity and environment.
- University of Minnesota: It pays for the studies.
- quote: He says "that despite different social economic
backgrounds, twins share many common
- conclusion: Many similarities in adopted twins suggest that
heredity may contribute to behaviors that we
normally associate with experience.
7 areas of similarity for twins separated at birth:
- Academic record
- Choice of occupation
- Sexual attraction
- Smoking/drinking/drug usage patterns
- Artistic abilities
- Musical abilities
- Athletic abilities
- Sexual orientation
- Naming of children/pets.
3 points researchers on heredity and environment:
1.) Many researchers now believe that many of the differences
among people can be explained by considering heredity as well
2.) Contrary to popular belief, the influence of genes on behavior
does not mean that nothing can be done to change the
3.) Although it is true that it is difficult and may be undesirable
to change the genetic code that may direct behavior, it is
possible to alter the environment in which the genes op