Download TRUTH Read

TRUTH
Read
the follovving
statements about psy
chology. Do you think
they are true or false? You
will earn whether each
statement is true or false as you read the chapter.
Individual cells in the human body can be several
feet long.
Anxiety can give you indigestion.
A person with brain damage may be able to report
that he or she has seen a face hut may not be able
to dentify that it was the face of a close friend.
Some people are ‘left-brained” and others are
“right-brained.”
The father’s genetic contribution —not the
mother’s—determines the sex of the offspring.
nincle possible iv the nervoi is vstein. \\‘hen we
learn a new ieii,t\ br or accjuire less’ ilitornial ion,
lie Hers ons s 1eni rt’bi-tei that eeriene i,ih
,hans in iL H mi no Lue im -i orasc.
‘he lit’ ‘St ls s\ 0 ciii Lm i o I R,tI n u ii o i be Ccii
toil ners ous oeni and He eriphr’rai nervous s\ s
‘iii, I He central nervous system Ii.it’, 0!
brain and tie spinal mi ri ihe peripheral nervous
sVStdfll is Iiiarfe rip of ner\ L ells that send near
between ihe cent ml nervous ss stem mcl ,iii t lie
paa is ol the liod\. In ordei to uiiderstali(l Loss the
cciii ml a id I he pr n pH ‘al iv rs ous 0 ems 0 01 l\
se niuo lirt rnirleiianrl Loss Hr rse cells conitnu
ii eat e oil h one ai lot her and hose i heir messapes
i no I iliroubli t lie liod,
Neurons
‘verve ‘e
ls, milled neurons, run throuh oui entire
1
indies and eennnin;o,ite o ‘H each oilier Neuron
-end and mm ei’ e iness,lbes from oilier st rum i ures in
lie hodv. srih as muscles and Hands. [hew CieS
I
The Nervous Svsiem
‘abes aii aiim i evenb rai’,iiivt Irom die seiisailOii 01
a lim
ml 0 eps ot
ci l ild I rein he
lie memory of a inst e\ ent. Lavh
of us has more than I hi) billion it tn’’ns most of
ss him Ii are found iii the brain,
rcK
0
the I
ne of a poem to I
I he 1 untiii iie r\ Oils vle iii is I nm ii s ed in bin Liii
dreamin, leelinb, ni(’\ ing. ,nicl iuu h more. Ii
0 H Kin ORCR o e nre octis e or t ill, no nl\e or
,isl ep. lb ners ous ss stem rehu Lies our inic mnl
smi tions. It is also nvolved m how oe react to I he
esienial world, [yen learn n and memors are
\vurons ii’m sonic
o lint lil\e trees in 0 rilr I ui’e Ru’ts of ie u i’ons reeni
He t lie branches. I run Is mu room H
ice. .\nd, is
The Anatomy of Two Neurons
Dendrites
Cell body
Nucleus
Myelin sheath
Synapse
I’
/
Axon
FIGURE 3.1
“Messages” enter neurons through the
dendrites. These messages are transmitted along the
54
e ti.otLe 3
trunklike axon to other neurons, glands, and muscles.
The myelin sheath protects the axon.
many nerve c uS ie alonesile one
her like a thicket ot trees. L nlike trees. how
neurons can also lie end to end. [heir “roots”
m ntcrt\vl ned it h the “branches I meurons i hat
helow see ligure 3. 1
Lvei’v neoroii consists ot a cll hodv, dendrites,
md an axon lie ccli body ii odtmces energy that
is the activity of the cell. Branching out from the
II bodx are thin tihems called dendrites, the den
ites receise molormation from other neuron
s and
ass the message through the cell body.
\Vhiie i lie dendrites carry mnlormation to lie cell
the axon carries mimessages uwtIV. .\ neuron has
any dendrites hut usualh a mIs one axon, Axons
mi-v greatly in length. ‘Nomne are umtst a 1 nv lractmon
1 an mcli. white 01 hers sI reich to several feet.
•ccause of’ the B ngth of their axons. sonic neui’ons
mm your legs are several feet long.
forests.
The Synapse
ii
/
Direction of nerve impulse
Axon terminal of
%—sending neuron
‘•
55
io:
NReceptor
site
Synapse
Neurotransmitters
It is true that individual ce/Is in
the body can be several feet
long. These cells are nerve
cells, or neurons, that are
onn becauw they have ong
ii
axons. Some of these neurons
u
are in the leg and are several feet long, stretching
from the lower spine to the toes.
TRUTH
Sacs containing
neurotransmitters
Dendrite of
receiving neuron
FiGURE 3.2 There is no physical connection between
neurons. A neuron relays its message across a junction
called a synapse by releasing chemicals called neuro
transmitters. They or received by the next neuron.
fictors include the locations of the neuron in the
body and the events that proctor ccl the message. I or
example. the pam in \larcs toe \s as
transmitted to his brain through sen
sory neurons. sensory neurons are
nerve cells that carry information
received by the senses to the cent raf
nervous system. Motor neurons, on
m lie other hand, are nerve cells that carry infornsa
ion I’ urn i lie cc ntral nervous system to the muscles
.aid the glands and influence their functioning.
Motor neurons took the message to \‘larci toot o
that lie pulled up on it and began to rub it. Other
motor neurons stimulated March glands
, making
his heart beat laster, Still other neurons in his brain
enabled bins to think over die matter and am decide
i hat I’ocld should lie forgiven.
ccasionalls something happens to disrupt the
nicssage-scnding process. For example. a hard blosv
n ii ie hear! irorn a car accident or a ports mnturv
can cause a concussion—an inlurv in ss hicli the soft
tisstie of the brain hits against tile skull. Sometnnes,
the person is affecter! for only a fw seconds. Other
times. t lie person may experience etfdcts for a much
longer time. In 1993, Dallas Cowboys c
uarterback
1
l’rov \ikman i’eceived a concussion during a game
in the National Bootball League plax oils. He
-
\lanv axons are cm erect ss a h rnvelin. a white
• tttv substance that insulates and protects the axon.
his mx cliii sheath, or casnio, also helps to speed
p the transmission of the message. At t lie end of
- ic axon. sinai icr fibers branc ii out. These fibors are
ailed axon terminals.
\lessages aie
cut from the axon terminaL of one neuron to the
iendrites of ot tier neurons. In order for a message
o be sent from one netiron to mother neuron, ii
oust cross the synapse. [le s\ napse is a unction
het\veen i lie axon ternnnals ol one neuron and the
lendrites of anot her neuron. Messages t ras ci in
niv one direction, [bus, niessages are received by
he dendrttes and travel through the Lil i is and
he axon to t lie axon terni nals. F’rons there, they
‘ross c\ napses to the ctcndntes of Other neurons.
See Ligure 3 2.) New synapses dan deselop
oet\s ccii neurons that were not previously
con
iterted, as when we learn somethmg new.
1 lie information that is sent and the place to
,vhtch it goes depend on a number of factors, These
PtOL(iGY .\Nt) ait I \\ ICR
55
are involved in r lie underlying biological process. In
addition, some diseases and psychological cl isor
tIers inas be caused hi he pi cseili e of too much or
I oo little of s anous neurotr imm titers.
Ruscais hers has e ideni died dozens ) iieti ro
transmitters and their I uilut ions. For exam P Ic,
t eivleholine is a common ncuroi ransiniiter that is
ins oh ed in the coni ‘of of muscles. It is
used by the motor neurons of t he
spinal cord amid sti inn ales skeletal
inticetec. I he release of aecr lcholt tie
ii as s’ hat dci to \lat’c
resDonse 1
eral’btng his loot.
I )opatniue is anot her ncuroi ransini it e r. ft is
involved primarily in imiotor In Eavioi’. .\ . L’Iiciencs
in dopaninc levels plo’. s a sic in Parl\ii Oiis his’
cjse, \\ lid i is char,n u riced bc it-c m us ii id tine
-
4%
Troy Aikman concussion in the 1993 football playotis interfered with his memory of the event.
remembers being at the game, b it he annot
remember what happened during the game. teli
zxnerienees show that memory is in large part a bio
logical process. t See Lhapter 7
oisimated. rigid nlo\cmcnts :\n cnss I dopamumne
nay ontribute to the psvcboogcal di
on her sclnz
5
pilmumlia. cc 1 hapici S.
ihcr imeurntrainnnttci include ioradicnalinc.
s’. htcli is pnnntritv ni is cd in ni’cpaiing the bod\
action and ci’Oh}iliil. n lti fitS tivlscd iii cnn
total at uisal md cli cp
Ii ouch is c are ofti n unaware of the processes iii
on noclis sic con he sums that our bodies ire fiord
\\ orE ii fmcthci sic are i unnnig or ottmg still. .\t
Veurotransmitterc:
Chemical Messengers
\urons send messages across synapses through
dac t elease of neurotransmitters. \eurotrans
mitters are chemicals that are stored in saks in the
axon terminals. ;\ neuron fires, or sends its messaec,
by releasing neui ti-ansrnitters—much like droplets
of water shooting out of a spray bottle I his ciii
occur hundreds of times ci cry second,
There are several types oi nctirotransntitters.
Each has its own specific structure and its into a
reecotor site in the next neuron, cnni lar to i he \\ a\
n which a key fits into a lock. [he message is e in
erteci into an electrical impulse that I ras c Is the
ungth of the neuron The message i hun i ranmn
d to the next neuron by neurotransmiiiers. EEc
li continues until the message arris es ai is
icstination. which in many eases is the brain. I its
hole process takes only a fraction oi a ser OilLl.
curot ransmitters are involved in sen thing
5
neople do. \\‘henever a person \vaves a hand.
urns, or ifitnlss about a frencl, neurotrancmittcvs
-
0
56
HPP I’ER 3
Long-distance runners experience a “runner’s high,”
which may be connected with the release of endor
phins. Endorphins are neurotransmitters similar in
function to the drug morphine. They have a tranquil
izing and painkilling effect on the body.
nv given moment, billions of neurons are shooting
ic urotransmi tters across synapses and sending
omplicated messages to various parts of the body
liese messages are carried via the spinal cord and
he peripheral nervous system.
(‘he central Nervous System
igure 3.3 shows the central nervous system, which
onsists of the neurons of the spinal cord and the
rain. (The brain is discussed in Section 2.) The
pina1 cord extends from the brain down the back.
It is a column of nerves about as thick as a thumb.
tnd it is protected by the bones of the spine, It
transmits messages between the brain and the mus
Ics and the glands throughout the body
The spinal cord is also involved in spinal
reflexes. A spinal reflex is a simple. automatic
response to something. For example, if a person
The Central Nervous System
Brain
Spinal
cord
ouches a hot stove, a message goes immediately
Irom his or her hand to the spinal cord. A message
to remove the hand is then sent back to motor neu
rons in the hand. fhe removal of the hand is a
spinal reflex. The person may also register pain in
his or her brain. But the nam s not what causes the
eflex. In fact, the pain may not even be felt until
ifter the hand has been removed.)
Many of our simple actions are reflexive. Have
ou ever wondered why you blink when you get a
)peck of dust in your eye? Or why some people
neeze when they sniff pepper? Physicians some
imes test people’s reflexes to learn whether their
iervous systems are functioning properly When a
doctor taps just below the knee to see if you kick,
he purpose is to check your knee-jerk reflex to
make sure your neurons are responding the way
hey are supposed to.
The Peripheral Nervous System
Ihe peripheral nervous system lies outside the cen
tral nervous system and is responsible for transmit
1ng messages between the central nervous system
and all parts of the body F he two main divisions of
he peripheral nervous system are the somatic ncr
ous system and the autonornic nervous system.
See Figure 3.4 on page 58.)
Ehe somatic
nervous system transmits sensory messages to the
.entral nervous system. It is activated by touch,
ain. changes in temperature, and changes in body
,osition. The somatic nervous system enables us to
5
II
FIGURE 3.3 Your spinal cord is protected by a col
umn of bones ca/led vertebrae. Similarly, your brain is
protected by the skull,
BIOLOGY AND BEHAVIOR
57
(4
moved or liiiieed position. It sends messages to
the muscles nid lie :la1Rls and helps us maintain
posture and balan e.
The word
autonoinic means “occurring involuntarily,’ or auto
matically. The autonomic nervous system regulates
the body vital lunctions, such as heartbeat, breath
ing, digestion, and blood pressure. We generally do
not have to think about these activities—they occur
automatically and are essential for keeping us alive.
Psychologists are interested in the autonomic
nervous system because of its involvement in the
experience of emotion. The response of the auto
nomic nervous system is particularly important
when a person experiences something stressful in
the environment.
The autonomic nervous system has two divi
sions: the sympathetic and the parasympathetic
nervous systems. (See Figure 3.-f.) These systems
generally have opposing functions. The sympa
thetic system is activated when a person is going
Into action, perhaps because of some stressful
event. It prepares the body either to confront the
situation or to run away This is sometimes called
the “fight-or-flight’ response. For example, when a
person is suddenly attacked by a large angry dog,
the sympathetic nervous system is aroused.
The sympathetic nervous system prepares the
body by suppressing digestion, increasing the heart
I
I
When the doctor hits your knee joint, sensory neurons
carry the message from the muscles to the spinal cord
and the brain. Motor neurons carry a message from
the brain back to the muscles, making your leg move.
experience the sensations of hot and cold and to feel
pain and pressure. For example. we can feel the
softness of a cat’s fur, warmth if the cat is sitting on
our lap, and pain if the cat scratches us. The somatic
system also alerts us that parts of the body have
Divisions of the Nervous System
[Nervous system
Central nervous system
Ii
Peripheral nervous system
I
Brain
4
1
I
Spinal
cord
Autonomic system (involuntary
muscles and internal organs)
Parasympathetic system
(calms body after emergencies)
FIGURE 3.4 This chart shows the major divisions of
the nervous system. The central nervous system consists
of the brain and the spinal cord. The peripheral nervous
58
(ZHAPTER3
“-“-.
Somatic system (voluntary
muscles and sense organs)
4
Sympathetic system
(prepares body for action)
system transmits messages from the central nervous sys
tem to all parts of the body.
I
id respiration rates, and elevating the blood pres
tie. Do you ever feel queasy when you are in a stress
ul situation—such as when your teacher springs a
ii prise quiz on you? This is because your sympa
thetic nervous system has kicked into
k
action and has suppressed your diges
tive processes. And when Todd stepped
on Marc’s toe, Marc felt his heart start to
race—another result of the activation
1I
of the sympathetic nervous system.
TRUTH
)
R E V
S
I E D
It is true that anxiety can give
you indigestion. Anxiety may
cause indigestion by induc
ing activity of the sympa
thetic nervous system, which
suppresses digestion.
before scientists had learned much about how the
brain functions, people did not attribute human
psychological processes such as thinking to the
working of the brain. People thought that what was
inside a person body was not very different from
what was inside an animal’s body Therefore, they
reasoned, the abilities that make people different
from animals—such as creative thought, art, and
analytical abilities—could not he explained in bio
logical terms. Instead, it was widely believed that
the body was inhabited by souls or demons.
The ancient Egyptians believed that a little per
sOfl dwelled within the skull and regulated behav
ior. The Greek philosopher Aristotle thought that
the soul had set up living quarters in the heart. B. F
Skinner iJ987) noted that the English language still
reflects the belief in the heart as the seat of will,
thought, hunger, and joy We use expressions such
as ‘deep in one’s heart,” “to know something by
heart,”
look into someone heart,” and ‘to have
change heart.”
Today. however,
that the mind,
consciousness, dwells within the brain (Goldman
Rakic, 1995; Sperry 1993). We know that when
thoughts of Linda ran through Marc’s
mind, something was happening in his
brain. We now have greater under
standing of (he brain and the links
between biological processes and psy
chological phenomena.
“to
In contrast to the cmpathetic system, the
virasympathetic nervous system restores the body’s
eserves of energy after an action has occurred.
leart rate and blood pressure are normalized,
hreathing is slowed, and digestion returns to nor
al, If you are having trouble remembering which
,‘ctem is which, perhaps it will help to keep in
nind that “sympathetic” and “stress” both start with
he letter s, while “parasympathetic” and “peace”
‘oth begin with p. [he sympathetic system reacts to
tress, the parasympathetic system restores peace.
a
of
we
recognize
or
Parts of the Brain
HINkING ABOUT PSYCHOLOGY
1. How do messages travel from one neuron
to another?
2. Identify the systems that make up the
peripheral nervous system.
3. Critical Thinking In what way do the
parasympathetic and the sympathetic ner
vous systems work together?
The Brain:
Our Control Center
‘very person is unique in part because of the capac
ies for learning and thought made possible by the
tuman brain. In ancient times, hundreds of years
The human brain is composed of many parts that
work together to organize our movements, create
our thoughts. form our emotions, and produce our
behaviors. rhe brain is divided into three sections:
the hindbrain, the midbrain, and the forebrain. (See
Figure 3.5 on page 60.) The hindbrain is the lower
portion of the brain and is involved in many vital
functions such as heart rate, respiration, and bal
ance. The midbrain includes areas that are involved
in vision and hearing. The forebrain, the front area
of the brain, is involved in complex functions such
is thought and emotion.
i
The medulla, the pons, and the
cerebellum are important structures of the hind
brain. rhe medulla is involved in vital functions
such as heart rate, blood pressure, and breathing.
The pons is located in front of the medulla and is
involved in regulating body movement, attention,
sleep, and alertness.
BIOLOGY AND BEHAVIOR
59
Parts of the Human Brain
FOREBRAIN
MIDBRAIN
o Reticular
activating
system
(middle
part)
A
Reticular
activating
system
(upper part)
A Thalamus
A Hypothalamus
A Cerebrum
Cerebral cortex
HINDBRAIN
LI
Reticular
activating system
(surface of
cerebrum)
Corpus
callosum
(lower part)
LI Medulla
LI Cerebellum
11 Poris
FIGURE 3.5
The average human adult brain weighs
about 3 pounds and has more than 10 billion cells, many
of which are neurons. Although the brain makes up about
‘ivix’lluni is the Latin word for little brain.’
The cerebellum looks like the larger part of the
brain (the cerebrum), tinder which it rests. hut it is
much smaller. It is involved in balance and coordi
rianon. A person whose cerebellum is injured may
have trouble with coordination. [he person may
walk unevenly and even occasionally fail doivn.
[he midbrain is located between
the hindbrain and the forebrain Areas within the
midbrain are involi ed in vision and hearing. Eve
movement, for example. is controlled by an area in
the midbrain. In addition, the midbrain contains
part of the reticular activating system. [lie reticu
ar activating system begins in the hinclbrain and
nes through the midbrain into the lower part of the
urchrain. F his system is tmiaortant [or attention.
60
CHAPTER 3
2 to 3 percent of a person’s body weight, it requires about
20 percent of the blood’s oxygen supply.
sleep. and arousal. Stimulation of the i’eticular acE
‘:ating system makes us alert. It aflcts arousal by
increasing heart rate and blood pressure, and it
increases brain activity some drugs, such as alco
hol, reduce the activity of the reticular activating
system, thus affecting alertness and reaction time.
sudden, loud noises stimulate the reticular acti
vating system and can awaken a sleeping person.
However, the reticular activating system can screen
out some noises A person who lives in the city may
not he awakened by the sounds of traffic roaring by
This same person ma however, awaken to sounds
that are more out of the ordinam such as a bird
singing, even tf these sounds are fairly soft.
Pour motor areas of the fore
brain al-c the thalamus. the hypothalamus, the
inic s\ stem. and he cerebrum. Certain iaarts of
forebrain are very well developed in human
ms. T’he forebrain is the part of the brain that
\cS it posinie for humans to cige in complex
nkmg processes.
I lxikuu its is a Latin word meaning ‘inner cham
The thalamus is a critical structure of the
un because it serves as a relay station for sensory
inulation. Most of the messages coming from the
use organs go through the thalamus on the way to
higher levels of the brain those areas responsi
for mental processes such as thinking and
[he halamus transmits
reas nuii’’
sensory information. Nueh as the pain
from \Iarey big toe, to the areas of the
brain that interpret and respond to the
in format ion, 1 he t halamus also relays
senorv input from the eves and the
of he brain kr inter
to the appropriate
.aation of the input
Hype- is a rreek prefix neaning “under. “Thus.
hypothalamus lies below i he thalamus. [he
pothalamus is \ cry tinu hut it is e\tremelv
mortani because it is in oh ed in many aspects of
havior and physiological functions. it is s ital to
regulation ot body temperature, the storage of
truents, and various aspects of mol Ration and
couon. It is also involved in hunuer. thirst, sexual
savior, earing br offspring, and ieression
turhances wit hin t lie hypothalamus can lead to
usual drinking and eating behaviors,
mong lower animals, stimulation of parts of
hypot halamus triggers behaviors such as fight
3, mating, or nest building. ,\lthough the hypo
1iamus is also ni p( )rtant to people. our behavior
ss nice hatuteaf and tends to be mtlueneed by
ininve tunenons such as thought, choice, and
ue systems.
The limbic system forms a fi inge along the
er edge of the cerebrum, It is mi oh ed in learn
and menior\ç motion, hunget, sex, and aggres
o If a narticular Ixurt of the limbie cvstem is
unaged. people can recall old memories but do
‘t create new memories. For example. a person
h clamape to that area may have vivid childhood
mnone of playing with his or her Nisler but may
ne able to memember that this Name sister i isited
1er that das Researchers have also found that
struction of mother specmfie area of the limbie
tem can leacf animals to show passive behavior.
‘struetion of a different area ol the limhie system
es sonic aniniais to behave ahgressivelv. even
en there ecnis title reason to do so.
.
[he cerebrum tLatin for “brain”) is the crown
ing glory of the brain, Only in human beings does
the cerebrum make up such a large part of’ the
brain. Ihe cerebrum accounts for about 70 percent
of’ the weight of the brain. [he surface of the cere
brum is wrinkled ii ith ridges and valleys. This sur
face is the cerebral cortex. cCo,’tcx is the Latin
word for “bark of’ a tree.’) The cerebral cortex is the
outer layer of the brain, lust as bark is the outer
layer of a tree.
[he cerebral cortex is the Irt of the brain that
we tend to think of when we talk about the brain. It
is the jrt that makes us uniciuufv human, the part
that thinks. In addition io thinking, the cerebral
cortex is also concerned with memory language.
emotions, complex motor functions. perception,
and much more.
The cerebral Cortex:
What Makes Us Unique
Phe cerebral cortex is composed of two sides—a
left side and a right side. Each side is called a hemi
sphere. (The Greek hemi- means “half.” Thus, each
half of the brain is half a sphere, just as each half of
planet Earth is a hemisphere. [‘o visuali:e the cere
bral cortex, think of a nalnnt. [he shell of the wal
iii it is like the skull. just as the walnut has tn o sides
that are connected. so does the brain. In the brain,
t lie structure that connects t lie two hemispheres is
called the corpus callosurn.
bntei’estmgly, information received by one side
of the body is transmitted to the opposite hemi—
sphere of the brain. Lor example, if you touch
sonic’thing u ith your left hand, that information is
sent to the right side of your brain. Conversely if
you t mcli soniething ii nh \ our right hand, the left
hemisphere om your brain receives the information.
[lie corpus eallosu in aids in getting in formation
from one side of the brain to the other.
Each hemisphere of the cerebral cortex is
dlii icIer! into four parts, or lobes. [he frontal lobe
lies behind the foi’eheacI. and the parietal lobe lies to
the top and rear of the hear!. I he temporal lobe lies
to m lie side. tust below the ears. I he occipital lobe is
at the back of the head. iSee Ligcire 3.n on page hl.)
Sonic sensations, such as visual sensations, are
received primarily in one lobe. Honever, each lobe
dloes not necessarily ac,t independently from the
others, Some functions require the interplay of sev
eral lobes. [he involvement of the cerebral cortex in
m lie Nenses and motor behavior is a good illustration
this interaction.
t3101.0CY AND BEHAVIOR
61
I
Sensory and Motor Areas of the Brain
Motor Area
Sensory Area
Legs
I Toes
• Trunk
Knees
• Head
Ships
C Shoulders
Arms
• Hands
O Fingers
O Face
Wrists
C Fingers
QNeck
C Eyes
Qjaw
o Ups
O Tongue
FIGURE 3.6
Certain areas of the cerebral cortex control specific sensory and motor functions.
fhe occipital
lobe contains the primary visual area of the cerebral
cortex. When light strikes the eyes, neurons in the
cipital lobe fire, enabling us to see. We also ‘see”
[lashes of light if neurons in the occipital lobe are
umulated b’ electricity
Damage to different parts of the occipital lobe
Lan create unusual conditions. People with damage
to one area may be able to recognize an object, but
hey may he unable to differentiate it from another
object that is similar. For example. if shown a key
they may know that what they see is a key but they
may not be able to tell it apart from another key that
looks different. People with damage to another area
62
CHAPTFR 3
may he able to report that they have seen a face, but
they may not be able to identify that itis the face of
a close friend,
It is true that a person with
brain damage may be able to
report that he or she has seen
a face but may not be able to
identify that it was the face of
REVI S
TED
a close friend. Damage to a
particular area in the occipital lobe of the cerebral
cortex can create this condition.
TRUTH
he hearmg, or auditory, area at the cortex lies
temporal lobe. Smnds are relayed [ram the
o the thalamus to the auditory area. \Vhen this
ii s, we hear sounds, It a specific area of the ternii cortex is cLmagecl, a persofl may not he able
cognize vers common sounds, such as a door
iinging.
\lessages received from the skin senses isee
pter 4 are pi’Olected to the sensory cortex in the
etal lobe. T’hee sensations include warmth and
cold odic h, and pain. Di ffbrent neu
rons fire, depending on whether you
has e c ratched your nose, touched a
hot sto\ e, or been stung by a bee.
\Vhrn rodd stepped on \larc toe, the
message was relayed from the toe
lie parieial lobe of \larc brain,
Ehe motor cortex mn he frontal lobe, However,
s involved when \lare grabbed his loot and
ted rubbing it. eurons in the motor cortex fire
icn we mos e certHin parts at our body \Vhen we
our hands or wiggle our toes, different parts of
frontal lobe ate si imtilated.
\\‘ei’nickc
which is locatedl in the temnno
ral lobe, pieces together sounds and sights. People
svith damage to this area may find it diffIcult to
undlerst and speech. I hey may he able to speak, hut
their speech often m meaningless. Par example,
when nked to describe a picture of two bays steal
ing cookies beh m nd a iss (mans bat Is, one
rLspondedl. ‘\lother is ann her working her work
to get her better. but when shey looking the two
boys looking the other part. hey working another
time” Geschwind, 1979.
Brocag
jN located in the frontal lobe near the
section at the motor cortex that controls the areas of
the face used for speaking. When Brocas area is
damaged. people speak slowly and laboriously
icing simple sentences. Lomprehension is d{tiite
.ooel. but they may speak only Ices’ svords. For
example, a person with Broea aphasia who wants
to say “the three bananas are lying on the table” may
produce onlI “bananas lie table,”
area,
person
area
The same
hemisphere that contains most language functions
also is usually
involved in logic, problem solv
ing. and mathematical computation than is the
other hemisphere i Borod. 1Q92
1 Hellige, 1990).
The nanlanguage hemisphere is relatis’elv more
concerned with the imagination, art, feelings, and
spatial relations.
In our society people often speak ol certain abil
as belonging to the right brain or to the left
brain. I htis, people ss ho ai’e very logical are said to
be ‘left-brained.’ svliile people who are partictilarly
reative are called “rteht-broinecl.’ This idea. hosv
c’s er, has become greatly exaggerated. Although
some differences do c.\ist, the hemispheres do not
act independently of each other (Hellige. 19901.
Lven t bough each hemisphere is capable of fune
mionine by itself, the brain functions better nhen
the two hemispheres svork together. One hemi
here does play a special role in language. ss bile
the other hemisphere plays a special role In feelings.
I losvevcr. both hemispheres are ins’olvcd in logic,
creativity and intuition.
more
\Itich of the cerebral cortex
omposed of areas that are directly responsible
ensory and motor functions. Other areas, called
‘ociation areas, serve mainly to shape informa
into something meaningful on which we can
For e\ample, some association areas piece
“ther sensory information. Certain neurons in
occipital lobe ‘ire when we
vertical lines.
crs fire when we ee hor:ontaf lines. .\ei ivitv in
association areas then integrates the information
iat we ee a meaningful form such as a tree, the
und, a swiriC set, or a letter of the alphabet. Other
ociation areas make possible such complex psv
logical ti in lions as thought and language.
o
view
Although the left and the
hemispheres of the brain have main’ of the
e functions, they differ mn a number of was s. For
nrple. for nearly all right-handed people, lan
lge lunctions are based m the left hemisphere.
I guage In nc t i on are a I o basedl in the left hem i
crc 1 about two out of three left-handed people.
nlv in a very small percentage of people arc
cuage I tmnct ions based in the right hemisphere.
‘A’ithin the hemisphere containing the language
‘cttons. two key language areas are Fracas area
I \\brnicke area. Damage to either area is likely
ause an aphasia, a dlifliculty with
inderstandling or producing language.
at
ities
-
specific
I’
I
aspects
TRUTH
‘d
-
ii
V i S
It is not true that some people
are “le ft-brained” and others
are “right-brained.” Both
hemispheres of the brain are
li’i involved in most human
I I F 0
activities and abilities.
IIt
L
1
O(IY .\\D t3EHA\’IOR
63
A common belief is that people who are very logical (such
as Judges) are “left-brained” whereas people who are
\ Inc Ii o I iv hat vvc h( ) lopi 5K have learned about
left- and right hemisphere functioning conies from
people ii ho len e had split brain operations
In a split-brat n operation. the corpus callosuni,
which connects the mo hemispheres. is cut. fbis
procedure. although performed only rareh3 is some
times med to help people with serious neural cbsorders such as severe eases of epilepsy. People with
epilepsy expenence sei:nrcs, which are bursts of
abnormal neuron firings that generally occur in one
hemisphere and then spread to the other. Lultnig
the corpus eallosum can reduce the severity of the
ei:rtre by pr’entiiig them from spreading. \fter
die uracrv, patients usually function quite dice
I vs lv dcpite their hemispheres inability to coni
111 Inmcate with cac hi othcr.
I loive er, the urger\ does have some subtle
ects on functmonmn. I or exaniple. people max ne
Oid to describe
crhallv the objects they hold in
leir riht hand hut not what they hold in their LIt
“and Kaz:aniga. I o I i h n is because if an object
held a ‘he siphi hind, the nilorination is ent to
tie let t I ieni nphere vhn h mi most neonle eon
tins ianguage abi lt1es Hawet er, f the same object
held m the tell hand, i hits inlormation is rjectccf
the right lie in nphe re. wh dii has cry little ian
Jijgc ability. Ii n important to cnicmher that for
spl’ \t ii Ii in! act corpus cailosums. the hemi
eneresin’,aI I it ‘ilc topet h r. In us, most people
in des nbc ,ibiccis held in either hand.
:‘
64
Il.’Th LR 3
more creative (such as artists) are “right-brained.” This
beliel, howeve,i has little scientific validity.
Jethods of Studying the i?raan
\luch A our earlier understanding of the brain
caine 1mm studies of people with head inJuries.
Foda\. researchers increase their l<nonleclge of the
brain and its functions by using a variety of tech
nid)uds to study damaged and intact brains.
One way that recearchers have been
able to see liotv the brain is related to psi chological
I tmncti( ns is through t lie studh of accidents and
brain damage. Brain damage from head injuries call
result in loss of \ ision and heaimng. r onhusion, nr
Ius of nieniorv In sonic cases, the l)s5 K laKe
0 t lie brain may result iii cia! ivelv little
0 unction. Yet the loss ul ital. niailer pails
can result in language problems. nicniorv loss, or
Peat Ii. In oilier words, which particular area is dam
iged may have a greater elfect than the amount of
lie damage.
b icc i neal
iniulauun uf i lie brain has hutvn that speemle’
o eas are associated wit Ii spcct lie R pes of w ncat i, ‘ns
ucli as seeing light or iceling a tap un the arm) or
motor activities (such as nalking).
c lassie research by Jo Lielgaclo I hoP) used
‘cctrical stmniulation ol (lie brain to hotv how an
annual could lie made to change behavioral ia!
merns. fhe researchers implanted an elect rode into a
p
ANDOTHER
STUDIES
STOR IES
TRUE
Is Phineas Gage Still the Same Man?
he ability of the
brain to withstand
some accidents is
nothing less than remark
able. In some instances,
people have not only sur
vived severe injuries to the
brain, but they have continued
to live fairly normal lives.
Sometimes, though, the victim is
not quite the same as before the
accident. Consider the case of
Phineas Gage.
Young Mr. Gage was a
promising railroad worker. His
character was outstanding and
SkUll
he was well liked. But all that
changed one day in 1 848. While
he was tamping down the blasting powder for a
dynamite charge, Gage accidentally set the pow
der off, and an inch-thick metal rod shot upward
through his brain and out the top of his head,
The rod landed many yards away. Gage fell
back in a heap. Yet he was not dead. His cowork
ers watched in shock as he stood up a few
moments later and spoke. They drove him by
oxcart to a local doctor, John Harlow. As the doc
tor marveled at the hole through Gage’s head,
Gage asked when the doctor thought he’d be able
to return to work.
Everyone, including the doctor, was surprised
that Phineas Gage even survived the accident.
Two months later, the physical effects of Gage’s
wounds had healed. He walked about, spoke nor
mally enough, and was aware of his surroundings.
However, Gage had changed. He no longer was a
dependable worker. He had also become foul
mouthed and ill-mannered. It had become clear
that the accident had had some serious psycho
logical consequences.
Gage died 1 3 years later during an epileptic
seizure. Dr. Harlow persuaded Gage’s family to
donate his skull to the Warren Medical Museum at
T
IA
4
Harvard University. Generations
of biologists and psychologists
have studied the skull and won
dered how Gage’s changes in
personality might have been
caused by damage to his brain.
According to biologists
Hanna and Antonio Damasio
(1992), the way in which the
rod had entered the brain had
spared the parts of the frontal
lobes that were involved in lan
guage and motor behavior.
Thus, Gage was able to speak
normally and move about easily.
However, the rod had severely
damaged a part of the under
side of the frontal lobes, causing
the disturbance in personality. The Damasios note
that people who suffer damage to the same part
of the brain today experience similar changes in
personality. These individuals are often unable to
censor their thoughts before speaking. As a result,
they may blurt out thoughts that they would have
kept to themselves before their brains were
injured.
Other researchers also have found changes in
patients’ personalities after brain injuries. In gen
eral, damage to right frontal areas can produce
impulsive and rule-breaking behaviors, such as
interrupting conversations (KoIb & Taylor, 1981).
People with frontal-lobe injuries are also less likely
to make spontaneous facial expressions. The com
bination of excessive talking and lack of facial
expressions may make these individuals seem like
different people than they were before.
Think About II
If a person suffers a major head injury in an acci
dent and then acts differently afterward, can we
assume that brain damage was responsible for the
personality change? Why or why not?
-
‘I
I
bully brain. \\ hen the brain was stimulated, the
bull dramatically stopped his charge and circled to
the right.
In another classic tucln James Olds and Peter
\lilner tOlds, 196) used rats who had electiocles
implanted in their brains to learn about the tune
ions ol the h\ pothalamus. \Vhen the rats pressed a
lever the electrodes stimulated the portion of the
hspothaiamus where they w re implanted. As it
turned out, the rats found this stimulation pleasur
able—so pleasurable that the rats would press the
lever up to 100 times a minute lust to reehe the
timulation. in some cases, hungry rats chose elec
trical stimulation os er food, hhe part of the hs po
thalamus where the electrodes were implanted thus
became known as a ‘pleasure center.’
Electrical stimulation of the brain is not always
reliable as a research tool, stimulation in the same
place can produce different effects at dilierent times.
(an one ocr aslon, a rat nay eat when a portion of
the brain is stimulated but on another occasion it
may drink. 1 he ateas that produce pleasant and
unpleasant scitsations hi lx’ople ma\ also sam from
rerson to p i on and from da\ to day
(he electroen
cephalogram i EEC) is a device that records the dcc
i rn al acuvi c of ihe brain. Elect rocles atta hcd to the
calp with tape or pacte detect small amounts of
electrical actisity called brain wases. Researchers
have learned that certain brain wave patterns are
issociated with feelings of ‘claxatmon and with
The photograph at left shows an image obtained by a
CAT scan. By producing a three-dimensional view of the
brain, a CAT scan can reveal hidden braIn damage. The
66
uFI’P (ER 3
deep. (See Chapter 5.) Researchers and physicians
can use electroencephalogram readings to help
diagnose some kinds of psychological disorders and
to help locate tumors.
in recent years, scientists have designed
new techniques for examining the brain. Fhese
techniques use computers to generate images of the
brain from various sources of information
(Coleman, 1995; Posner & Raichie. 1994). Images
of the brain can provide information about brain
damage and other abnormalities. Imaging tech
niques can also he used for early diagnoses of can
cers and other problems. In addition, physicians
ran use imaging to aid them during dill ic nIt and
intricate surgeries.
In computerized axial tomography ((‘AT) scans,
i mosing ring passes X-ray beams around and
through the head. ihe density of the brain tissue
determines how muc h radiation is absorbed.
omputers measure the amounts of radiation and
piece together a three-dimensional view of the brain
that can be displayed on a ideo monitor.
In magnetic resonance imaging \4R1), a person
irs in a very powerful magnetic field, Radio waves
then cause parts of the brain to give off extra energy
1 his energy is measured from multiple angles and is
i m’anslaied by computer into a visual image of the
brainy anatomy kIRI is more powerful than a CAT
scan and can show details more clearly [‘or examile, MRI is more effective at revealing small injuries
and abnormalities in hard-to-see areas.
photograph on the right shows a person entering MRI
apparatus. For people who fear enclosed spaces, the time
spent lying in the MRI field can be uncomfortable.
Pos
itron emission tomography (PE
T scans Jib
Irom CAT scans and MRI becaus
e they show the
ivity of the brain rather than
a
snapshot of the
un at a given time. scientists
can see the brain
I nally at work. The per
son is injected wtth
lioactive sugar. As the sugar reac
hes the brain,
re of it is used \\ here bra
in activiI is greater. A
unputer image is generated based
on the activity
e PET scan has been used by
researchers to see
ach parts of the brain are most
active when we
listening to music, workin
g out a math problem.
ng language, or plas np chess uol
clmanRakie,
P5; Raichle. I 9P4, The
PET scan reveals which
i_Is of the brain are activated
u tide the event is
uallv taking place Po, if you rais
e your hand, the
unputer u ill show act ivdv in one
area. If von sud
ily start to sing a song, another area
will light up.
Tsing these rese
arch techniques, psychologists
ye learner! that the mind i a un
duet of the I nain.
day it is generally agreed that
for every mental
nt, such as a thotieht or a feel
ing, there are
umpanving. rtnuierlvng biolog
ical events.
laging teLhniques have allowed
us to explore
we deeply how the nervous stem
, particularly
hrin, lunctuons u hlc
e are 1
thtn
n
gk
, feeling,
J moving. The study of brain abn
ormalities has
o revealed that the brain has gre
at flexibility In
er words, when parts of the bra
in have under
ne damage. other areas of the
brain can some
nes take over the functions ot the
damager! areas.
NINKIN ABOUT PSYCHOLOGY
I. \Vhv is the cerebral cortex imp
ortant?
2. Describe two differences betw
een the left
hemisphere and the right hemisph
ere of
the cerebral cortex.
3. List three different imaging tech
niques
used to study the brain.
4. Critical Thinking Wh
y do you think
it benefits people to have
brains that are
ilexihie? What would happen if
brains
were riot flexible?
3
The Endocrine SysLem
e endocrine system consists
of glands that
rete substances, called
hormones, into the
odstrearn. The word Iiou,nonc
is derived
from the
A PET scan shows brain activity
as it occurs.
(reek Iiorniun. meaning io
stunulae’ or ‘to
Hormones stimulate growth
and many
kinds of reactions. ue h as change
s in act ivuv levels
and moods. Because hormones
affect behavior and
emotional reactions. pss cholog
ists \vho study the
biology of behavior are
also interested in the
endocrine system
Like neurotransnutters hormo
ne ha\ e specti;c
receptor sites. Although the var
ious hormones cir
culate throughout the body, thes
act on l\ on hor
mone receptors ui Lertai n
places. I lormones are
prod riced by eve nil differen
t glands. l’hcse glands
include the
rv gland, the thyroid gland, the
adrenal glands, and he testes
and the ovaries. u ce
Lipure 3.7 on page Pb.)
excite.
e Pituitary Gland
7hc
S
itriltarv gland
lies just below the hvpothala
‘s about the sire of a pm. but it
is so impor
tint (ha t has been referred
to as the ‘maste
gland.’ Ilic itrumary gland, whi
ch is stimulate y
the hvpothak us, is responsible
for the s’ etion
of many differ
hormones that af fe
various
:lspeets of hehavioi,
ro\th hormone, or example
regulates the
growth of muscles, ho
s, anc glands
hmldren
hose growth patterns see
ormallv slow often
catch up to others the San
e u lien doctors give
them Cro\vth hormone,
onie hormones feet fem
a
in relation to
regnamc’ and in lering.
Probe tin s iulates pro
c[uction of
mus.
‘
I
‘
rn
in nursing women.
‘voemn is
responsibl
or timulating labor
in p unant
\voineil, onietunes sr hen a
pi’egnant u oma is
over
,an obstetrician may induce labo
r by injee
in e noman \\ith oxytocin.
BlOT Y
1
O
r A’xI) BEH\VIOR
67
H.
4