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C H A P T E R
1
What Are the Origins of Brain
and Behavior?
Human Evolution
Focus on Disorders: Traumatic Brain Injury
Humans: Members of the Primate Order
Why Study Brain and Behavior?
Australopithecus:Our Distant Ancestor
Focus on Disorders: Linking Brain Function to Brain
The First Humans
Injury
What Is the Brain? Evolution of the Human Brain
Gross Structure of the Nervous System
Brain Size and Behavior
What Is Behavior?
Why the Hominid Brain Enlarged
Perspectives on Brain and Behavior
Studying Brain and Behavior in
Aristotle and Mentalism Modern Humans
Descartes and Dualism
Fallacies of Human Brain-Size Comparisons
Focus on New Research: The Origins of Spoken
Culture
Language
Focus on Disorders: Learning Disabilities
Darwin and Materialism
Evolution of Brain and Behavior
Origin of Brain Cells and Brains
Classification of Life
Evolution of Animals with Nervous Systems
The Chordate Nervous System
Left:Oliver Meckes/Ottawa/Photo Reseachers. Middle:Crandall/The Image
Works. Right:CNRI/Phototake.
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Traumatic Brain Injury
F E ach year a reported 80,000 people in
A variety of mechanical
o
the United States of America experi- forces cause traumatic
c
brain injuries as a result
ence long-term disability from complica-
u
of a blow to the head.
s tions related to head trauma (Brain Injury
Association, 2002). Traumatic brain in-
o
n juries are the leading cause of both death
The damage at the site of impact is
and disability among children and teen-
D called a coup (shown in pink).
agers (Cassidy et al., 2004). What is it like
i Direction of blow Direction of blow
s to be brain injured? Fred Linge, a clini-
o
The pressure resulting from a coup
cal psychologist with a degree in brain
r produce a countercoup on the
d research, wrote this description 12 years opposite side of the brain (shown
e after his traumatic brain injury occurred: in blue).
r
s
In the second it took for my car to Movement of the brain may shear nerve
crash head-on, my life was perma- fibers, causing microscopic lesions, especially
in frontal and temporal lobes. Blood trapped
nently changed, and I became another in the skull (hematoma) and swelling (edema)
statistic in what has been called “the cause pressure on the brain.
silent epidemic.”
I have met seems to go through this stage of narcis-
During the next months, my family and I
sistic preoccupation, which creates a necessary
began to understand something of the reality of the
shield to protect them from the painful realities of
experience of head injury. I had begun the painful
the situation until they have a chance to heal.) I had
task of recognizing and accepting my physical,
very little sense of anything beyond the material
mental, and emotional deficits. I couldn’t taste or
world and could only write about things that could
smell. I couldn’t read even the simplest sentence
be described in factual terms. I wrote, for example,
without forgetting the beginning before I got to the
about my various impairments and how I learned to
end. I had a hair-trigger temper that could ignite in-
compensate for them by a variety of methods.
stantly into rage over the most trivial incident.
At this point in my life, I began to involve my-
During the first year, I could not take too much
self with other brain-damaged people. This came
stimulation from other people. My brain would
about in part after the publication of my article. To
simply overload, and I would have to go off into
my surprise, it was reprinted in many different
my room to get away. Noise was hard for me to
publications, copied, and handed out to thou-
take, and I wanted the place to be kept quiet,
sands of survivors and families. It brought me an
which was an impossibility in a small house with
enormous outpouring of letters, phone calls, and
three youngsters in it. I remember laying down
personal visits that continue to this day. Many
some impossible rules for all of us. For example, I
were struggling as I had struggled, with no diag-
made rules that everybody had to be in bed by
nosis, no planning, no rehabilitation, and most of
9:30 PM, that all lights had to be out, and that no
all, no hope. . . . The catastrophic effect of my in-
noise of any kind was permitted after that time. No
jury was such that I was shattered and then re-
TV, radios, or talking was allowed. Eventually the
molded by the experience, and I emerged from it
whole family was in an uproar.
a profoundly different person with a different set
Two years after my injury, I wrote a short arti-
of convictions, values, and priorities. (Linge, 1990)
cle: “What Does It Feel Like to Be Brain Damaged?”
At that time, I was still intensely focusing on myself The diffuse effects of traumatic brain injury make diag-
and my own struggle. (Every head-injured survivor nosis very difficult, which is why brain injuries have been
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2 ! CHAPTER 1
collectively called a “silent epidemic.” Victims of severe brain injuries resulting from motor vehicle accidents are
traumatic brain injury can suffer serious repercussions in particularly severe because the head is moving when the
their everyday lives. Like Fred Linge, many have difficulty blow is struck, thereby increasing the velocity of the impact.
returning to their former levels of functioning, including In the years after his injury, Fred Linge made an im-
carrying out the jobs that they held before injury. mense journey. Before the car crash, he gave less thought to
Traumatic brain injury results from a blow to the head the relation between his brain and his behavior than he did
that subjects the brain to a variety of forces shown on the to tying his shoes. At the end of his journey, adapting to his
accompanying illustration: injured brain and behavior dominated his life. He became
a consultant and advisor to other people who also had suf-
The force exerted on the skull at the site of the blow
fered brain injury.
causes a contusion (bruising) known as a “coup” (French
The purpose of this book is to take you on a journey to-
for a strike or blow).
ward understanding the link between brain and behavior:
The blow may force the brain against the opposite side
how the brain is organized to create and monitor behavior
of the skull, producing an additional contusion called a
and what happens when the brain is not functioning properly.
“countercoup.”
Much of the evidence comes from studying three sources: the
The movement of the brain may cause a twisting or
evolution of brain and behavior in diverse animal species,
shearing of nerve fibers, resulting in microscopic lesions
how the brain is related to behavior in normal people, and
(damage to the nervous system). Such lesions may be found
changes in people who suffer brain damage or other brain ab-
throughout the brain, but they are most common at the
normalities. The knowledge emerging from the results of
front and sides.
these studies is changing how we think about ourselves, how
The bruises and strains caused by the impact may pro-
we structure education and our social interactions, and how
duce bleeding (hemorrhage).The blood trapped within the
we aid those with brain injury, disease, and disorder.
skull acts as a growing mass (hematoma),which exerts pres-
In this chapter, we answer the question, What are the
sure on surrounding brain regions.
origins of brain and behavior? We begin by defining both
Like blows to other parts of the body, blows to the
brain and behavior and outlining the nervous system’s basic
brainproduce edema(swelling), a collection of fluid in and
structure. We then take a historical look at three major the-
around damaged tissue. Edema is another source of pres-
ories concerning the relation between brain and behavior.
sure on the brain.
From this background, we explore the evolution of brain
People who sustain traumatic brain injury often lose and behavior, showing how the brain and complex behavior
consciousness because the injury affects nerve fibers in emerged and changed as animals evolved. Finally, we con-
lower parts of the brain associated with waking. The severity sider how the human brain has adapted to its most complex
of coma can indicate the severity of the injury. Traumatic function—culture.
WHY STUDY BRAIN AND BEHAVIOR?
The brain is a physical object, a living tissue, a body organ. Behavior is action, mo-
mentarily observable,but fleeting.Brain and behavior differ greatly but are linked.
The brain was once thought to play little or no role in behavior,and so the study
of brain function was seen as a biological pursuit not central to psychology. Even
today,many students view the brain as peripheral to understanding human behavior.
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WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 3
Linking Brain Function to Brain Injury
F The case history of Phineas Gage is a source of early insight after the accident, his behavior changed completely. Harlow,
o
into how the brain controls behavior (MacMillan, 2000). in describing the case, wrote:
c
u Gage was a 25-year-old dynamite worker on a railroad bed
The equilibrium or balance, so to speak, between
s construction site who in 1848 survived an explosion that
his intellectual faculties and animal propensities
o blasted an iron tamping bar (about a meter long and 3 cen-
seems to have been destroyed. He is fitful, irrever-
n
timeters wide) through the front of his head (see photo-
ent, indulging at times in the grossest profanity,
D graph). Surprisingly, quite a few people have survived similar
manifesting but little deference to his fellows,
i injuries, even from tamping bars, but Gage’s physician, John
s impatient of restraint or advice when it conflicts
o M. Harlow, wrote an account of Gage’s accident and this ac-
with his desires, at times perniciously obstinate, yet
r count helped propel Gage to fame.
d capricious and vacillating, devising many plans of
Gage had been of average intelligence and very indus-
e
operation, which are no sooner arranged than they
r trious and dependable. He was described as “energetic and
s are abandoned in turn for others appearing more
persistent in executing all of his plans of operation.” But,
feasible. A child in his intellectual capacity and
manifestations, he has the animal passions of a
strong man. (Blumer and Benson, 1975, p. 153)
mage owa.
d Iof I The remarkable feature of Gage’s frontal-lobe injury is
epartment of Neurology anAnalysis Facility, University tmlohof eawfnto tprhser;eso hivgdiishidd teb adrnan oeidntv ipdidnlieasjunnprcnlayeiy n m tgho.aabitnv tilhoye ua sff rfeomcnottetaodl r l hooibsr epms ewersmeoronera yllo iticyma. tpHioaainrrs--
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Although the tamping bar and Gage’s skull have been
preserved, Gage’s precise injury could not be described, be-
cause no autopsy was performed after his death and so the
actual damage produced by the tamping bar could not be de-
termined. Measurements from Gage’s skull and modern im-
Reconstruction of Gage’s brain injury with the use of modern aging techniques have been used to reconstruct the accident
imaging techniques. From “The Return of Phineas Gage: Clues about the
and determine the probable location of the lesion. The frontal
Brain from the Skull of a Famous Patient,” by H. Damasio, T. Grabowski, R. Frank,
A. M. Galaburda, and A. R. Damasio, 1994, Science, 20,p. 1102. cortex of both hemispheres appears to have been damaged.
Yet the brain and behavior have evolved together: one is responsible for the other,
which is responsible for the other,which is responsible for the other,and so on and
on.A classic example of the control exerted by the brain on behavior is illustrated in
“Linking Brain Function to Brain Injury.”
Nearly 150 years after French neurologist Jean Charcot first autopsied patientswho
died ofbrain diseases and related their symptoms to their pathology,theaccumulated
research suggests three reasons for linking the study ofbrain and behavior:
1. A growing list of behavioral disorders can be explained and possibly cured by
understanding the brain.Indeed,more than 2000 disorders may in some way be
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4 ! CHAPTER 1
related to brain abnormalities. As indexed in Table 1-1, throughout this book,
especially in the “Focus”sections,we detail relations between brain disorders and
behavioral disorders.
2. The brain is the most complex living organ on Earth and is found in many differ-
ent groups of animals.Students of the brain want to understand its place in the
biological order of our planet.Chapter 1 describes the basic structure and evolu-
tion of the brain,especially the human brain,and Chapters 3 through 5 describe
the function of brain cells—cells that are common to all animals that possess a
nervous system.
3. How the brain produces both behavior and human consciousness is a major
unanswered scientific question. Many scientists and students study the brain
from the philosophical perspective of understanding humanity. Many chapters
in this book touch on the relation between psychological questions related to
brain and behavior and philosophical questions related to humanity.For exam-
ple,in Chapters 13 and 14,we address questions related to how we learn and how
we think.
None ofus can predict the ways in which knowledge about the brain and behavior may
prove useful.One former psychology major wrote to tell us that she took our course
only because she was unable to register in a preferred course.She felt that,although
our course was interesting,it was “biology and not psychology.”After graduating and
getting a job in a social agency,she found to her delight that,by understanding the links
Table 1-1 Index of Disorders Discussed in Chapters 1 through 15
Addiction 7 Brain tumors 3* Insomnia 12 Phenylketonuria 15
ADHD 15 Carbon monoxide poisoning 8* Korsakoff’s syndrome 13* Posttraumatic stress disorder 7
Affective disorders 11*, 15 Cerebral aneurysm 9* Learning disabilities 1*, 6 Presbyopia 8*
Agenesis of the frontal lobe 11* Cerebral palsy 6*, 10 Lou Gehrig’s disease 4* Psychosis 7
Agnosia 8 Closed head injury 1* Mania 15 Quadripelegia 10
Alzheimer’s disease 5, 13*, 15 Contralateral neglect 14 Meningitis 2* Restless legs syndrome 12
Amnesia 13 Dementia 15 Mental retardation 6 Schizophrenia 5, 6*, 7, 15
Androgen insensitivity syndrome 11* Demoic acid poisoning 7 Migraine 8* Scotoma 8
Androgenital syndrome 11* Depression 5, 7, 11*, 15 Missile wound 1 Seasonal affective disorder 12*
Anencephaly 6 Down’s syndrome 3 MPTP poisoning 5* Sleep apnea 12*
Anorexia nervosa 11 Drug-induced psychosis 7* Multiple sclerosis 3*, 15 Spinal-cord injury 10, 11
Anxiety disorders 11*, 15 Encephalitis 2* Myasthenia gravis 4* Split-brain syndrome 14
Aphasia 9 Environmental deprivation 6* Myopia 8* Stroke 2*, 15
Apraxia 10 Epilepsy 4, 9*, 15 Narcolepsy 12 Synesthesia 14*
Arteriovenous malformations 9* Fetal alcohol syndrome 7* Obesity 11 Tay-Sachs disease 3
Asperger’s syndrome 15 Frontal leucotomy 11 Obsessive compulsive Tourette’s syndrome 5, 10*
Ataxia 8 Hemianopia 8 disorder 5, 7 Traumatic brain injury 1*, 15
Autism 10* Huntington’s chorea 3* Panic disorder 11*
Bell’s palsy 2* Hyperopia 8* Paraplegia 10*
Bipolar disorder 15 Insanity 1* Parkinson’s disease 5*, 15
Note: Name of disorder is followed by chapter number(s).
*Disorder is subject of “Focus on Disorders.”
Abbreviations: ADHD, attention deficit hyperactivity disorder; MPTP, methylphenyltetrahydropyridine.
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WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 5
between brain and behavior,she had insight into the disorders of many of her clients
Hemisphere. Literally, half a sphere,
and treatment options for them.So let’s begin,by defining first the brain,then behav-
referring to one side of the cerebral cortex
ior,and finally how they evolved together. or one side of the cerebellum.
Cerebral cortex. Outer layer of brain-
tissue surface composed of neurons; the
What Is the Brain?
human cerebral cortex contains many
folds.
For his postgraduate research,our friend Harvey chose to study the electrical activity
that the brain gives off.He said that he wanted to live on as a brain in a bottle after his
body died.He expected that his research would allow his bottled brain to communi-
cate with others who could “read”his brain’s electrical signals. Harvey mastered the
techniques of brain electrical activity but failed in his objective,not only because the
goal was technically impossible but also because he lacked a full understanding ofwhat On the Foundations of Behavioral
“brain”means. NeuroscienceCD, visit the module on the
Brainis the Anglo-Saxon word for the tissue that is found within the skull,and it central nervous system. Go to the overview
is this tissue that Harvey wanted to put into a bottle.The brain has two almost sym- and look at the three-dimensional view of
metrical halves called hemispheres, one on the left and one on the right. So, just as the human cortex for a hands-on view of
your body is symmetrical,having two arms and two legs,so is the brain.Figure 1-1A what this organ looks like. (See the Preface
shows the left hemisphere of a typical human brain oriented in the upright human for information about this CD.)
skull.Ifyou make a fist with your right hand and hold it up,the fist can represent the
positions of the brain’s broad divisions, or lobes, within the skull, with the thumb
pointing toward the front (Figure 1-1B).
The entire outer layer of the human brain consists of a thin,folded layer of nerve
Figure 1-1
tissue,the cerebral cortex,detailed in the sectional view in Figure 1-1A.The word cor-
The Human Brain (A) The cerebral
tex,Latin for the bark of a tree,is apt,considering the cortex’s heavily folded surface
cortex of the nearly symmetrical
and its location in covering most ofthe rest ofthe brain.The grooves ofthe cortex are
hemispheres of the brain is divided into
called sulci and the bumps are called gyri.Unlike the bark on a tree,they are not ran-
four lobes. The cerebral cortex is a thin
dom folds but demark functional zones.Later on,we’ll provide their names and func- sheet of nerve tissue that is folded many
tions.The cortex of each hemisphere is divided into four lobes,named after the skull times to fit inside the skull, as shown in
bones beneath which they lie. the sectional view. (B)Your right fist can
serve as a guide to the orientation of
the brain’s left hemispheres and lobes.
(A) Sectional view (B)
Lobes define broad The brain is made up Bumps in the brain's Cerebral cortex Your right hand, if made into a
divisions of the of two hemispheres, folded surface are is the brain’s fist, represents the positions of
cerebral cortex. left and right. called gyri, and cracks thin outer the lobes of the left hemisphere
are called sulci. “bark” layer. of your brain.
Top
Parietal lobe
Parietal (knuckles)
Frontal lobe Occipital lobe
lobe
Frontal (fingers) (wrist)
lobe
Front Occipital
Temporal lobe
Back
lobe
Bottom
Temporal lobe
ers (thumb)
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arc
Rese
o
ot
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6 ! CHAPTER 1
The forward-pointing temporal lobe is located at the side of the brain,approxi-
Temporal lobe. Cortex lying below the
mately the same place as the thumb on your upraised fist. Immediately above your
lateral fissure, beneath the temporal bone
at the side of the skull. thumbnail,your fingers correspond to the location of the frontal lobe, so called be-
cause it is located at the front of the brain,beneath the frontal bone of the skull.The
Frontal lobe. Cerebral cortex anterior to
the central sulcus and beneath the frontal parietal lobe is located beneath the parietal bone at the top of the skull, behind the
bone of the skull. frontal lobe and above the temporal lobe.The area at the back ofeach hemisphere be-
Parietal lobe. Cerebral cortex posterior neath the occipital bone constitutes the occipital lobe.
to the central sulcus and beneath the Harvey clearly wanted to preserve not just his brain but his self—his conscious-
parietal bone at the top of the skull. ness,his thoughts,his intelligence.This meaning ofthe term brainrefers to something
Occipital lobe. Cerebral cortex at the other than the organ found inside the skull.It refers to the brain as that which exerts
back of the brain and beneath the control over behavior.
occipital bone.
This meaning of brainis what we intend when we talk of someone being “the
Neuron. A brain cell engaged in brain”or when we speak ofthe computer that guides a spacecraft as being the vessel’s
information processing.
“brain.”The term brain,then,signifies both the organ itselfand the fact that this organ
Spinal cord. Part of the central nervous controls behavior.Why could Harvey not manage to preserve his control-exerting self
system encased within the vertebrae or
inside a bottle? Read on to learn one answer to this question.
spinal column.
Central nervous system (CNS). The
brain and spinal cord.
Gross Structure of the Nervous System
Peripheral nervous system (PNS). All
the neurons in the body located outside
Just like every other organ of the body,the brain is composed of billions of cells that
the brain and spinal cord.
come in a variety ofshapes and sizes.One type ofbrain cell is the neuron(sometimes
Sensory neuron. Neuron that carries
called nerve cell),and neurons are the cells that most directly control behavior.Neu-
incoming information from sensory
receptors into the spinal cord and brain. rons have long processes called axons and dendrites that allow them to communicate
with one another,with sensory receptors on the body,with muscles,and with internal
Motor neuron. Neuron that carries
information from the spinal cord and body organs.
brain to make muscles contract. The nervous system consists oftwo main subdivisions:the central nervous system
and the peripheral nervous system.Most ofthe connections between the brain and the
rest of the body are made through the spinal cord, which descends through a canal
inthe backbone.Together,the brain and spinal cord make up the central nervous sys-
tem (CNS),as shown in Figure 1-2.Thus the CNS is encased in bone,the brain by the
skull and the spinal cord by the vertebrae.It is “central”both because it is physically lo-
cated as the core of the nervous system and because it is the core structure mediating
behavior.
Use the FoundationsCD to look at All the nerve processes radiating out beyond the brain and spinal cord as well as
how these nerve networks work in our all the neurons outside the brain and spinal cord constitute the peripheral nervous
brains. The overview of the brain in the system (PNS).An extensive network ofsensory neurons in the PNS connect to recep-
central nervous system module includes a tors on thebody’s surface,internal organs,and muscles to gather sensory information
rotatable, three-dimensional view of the for the CNS.Motor neurons in the PNS convey information from the CNS to move
brain that will help you visualize how all muscles ofthe face,body,and limbs.Motor neurons also govern the workings ofyour
these parts fit together. body’s internal organs,autonomic functions,such as the beating ofyour heart,the con-
tractions ofyour stomach,and the movement ofyour diaphragm to inflate and deflate
your lungs.
To return to the question of Harvey’s brain-in-a-bottle experiment,the effect of
placing the brain or even the entire CNS in a bottle would be to separate it from the
PNS and thus to separate it from the sensations and movements mediated by the PNS.
How would the brain function without sensory information and without the ability to
produce movement?
In the 1920s,Edmond Jacobson (1932) wondered what would happen ifour mus-
cles completely stopped moving,a question relevant to Harvey’s experiment.Jacobson
believed that,even when we think we are entirely motionless,we still make subliminal
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WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 7
movements related to our thoughts.The muscles of the larynx
Central nervous system (CNS)
subliminally move when we “think in words,”for instance,and
The brain and spinal cord, those parts of the
we make subliminal movements of our eyes when we imagine nervous system that are encased by the skull and
or visualize a scene.So,in Jacobson’s experiment,people prac- vertebrate bones
ticed “total”relaxation and were later asked what the experience
Peripheral nervous system (PNS)
was like.They reported a condition of“mental emptiness,”as if Neurons and nerve processes outside CNS
the brain had gone blank.
In 1957,Woodburn Heron investigated the effects of sen- Sensory connections
sory deprivation,including feedback from movement,by hav- to receptors in the
skin
ing each subject lie on a bed in a bare,soundproof room and
remain completely still. Tubes covered the subjects’ arms so
Motor connections
that they had no sense of touch, and translucent goggles cut
to body muscles
off their vision.The subjects reported that the experience was
extremely unpleasant, not just because of the social isolation
but also because they lost their normal focus in this situa- Sensory and motor
connections to internal
tion. Some subjects even hallucinated, as if their brains were
body organs
somehow trying to create the sensory experiences that they
suddenly lacked.Most asked to be released from the study be-
fore it ended. Figure 1-2
Findings from these experiments suggest that the CNS Gross Structure of the Human Nervous
needs ongoing sensory stimulation, including the stimulation System In essence, the nervous system
that comes from movement,ifit is to maintain its intelligent ac- interprets sensory stimulation and
tivity.Thus,when we use the term brainto mean an intelligent, produces behavior.
functioning organ,we should probably refer to an active brain
that is connected to the rest of the nervous system.Unfortunately for Harvey,that a
brain in a bottle, disconnected from the PNS, would continue to function normally
seems very unlikely.
What Is Behavior?
Irenäus Eibl-Eibesfeldt began his textbook,Ethology: The Biology ofBehavior,published
in 1970,with the following definition:“Behavior consists of patterns in time.”These
patterns can be made up ofmovements,vocalizations,or changes in appearance,such
as the movements associated with smiling.The expression “patterns in time”can even
include thinking.Although we cannot directly observe someone’s thoughts,techniques
exist for monitoring changes in the brain’s electrical and biochemical activity that may
be associated with thought.So thinking,too,forms patterns in time.
The behavioral patterns of some animals are relatively fixed;that is,most of their
behaviors are inherited ways of responding.The behavioral patterns of other animals
are both inherited and learned.If all members of a species display the same behavior
under the same circumstances, that species has probably inherited a nervous system
evolved to produce that relatively fixed behavioral pattern automatically.In contrast,if
each member ofa species displays a somewhat different response in a similar situation,
that species has inherited a much more flexible nervous system that is capable of
changes in behavior due to learning.
An example of the difference between a relatively fixed behavioral pattern and a
more flexible one is seen in the eating behavior of two different animal species—
crossbills and roof rats—as illustrated in Figure 1-3.A crossbill is a bird with a beak
that seems to be awkwardly crossed at the tips;yet this beak isexquisitely evolved to
eat certain kinds of pine cones.When eating these pine cones, crossbills use largely
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8 ! CHAPTER 1
fixed behavioral patterns that are inherited and do not require much modification
A crossbill's beak is
through learning.
specifically designed to
open pine cones. This If the shape of a crossbill’s beak is changed even slightly by trimming,the bird is
behavior is innate. no longer able to eat preferred pine cones until its beak grows back.Roofrats,in con-
trast,are rodents with sharp incisor teeth that appear to have evolved to cut into any-
thing.But roofrats can eat pine cones efficiently only ifthey are taught to do so by an
experienced mother.
The behavior described here is limited to pine-cone eating,and we do not intend
to imply that all behavior displayed by crossbills is fixed or that all behavior displayed
by roof rats is learned.A central goal of research is to distinguish between behaviors
that are inherited and those that are learned and to understand how the nervous sys-
tem produces each type ofbehavior.
The complexity ofbehavior varies considerably in different species.Generally,an-
A baby roof rat must
learn from its mother imals with smaller,simpler nervous systems have a narrow range ofbehaviors.Animals
how to eat pine cones. with complex nervous systems have more behavioral options.We humans believe that
This behavior is learned.
we are the animal species with the most complex nervous system and the greatest ca-
pacity for learning new responses.
Species that have evolved greater complexity have not thrown away their simpler
nervous systems, however. Rather, complexity emerges in part because new nervous
system structures are added to old ones.For this reason,although human behavior de-
pends mostly on learning,we,like other species,still possess many inherited ways of
Figure 1-3 responding.The sucking response ofa newborn infant is an inherited eating pattern in
humans,for example.
Innate and Learned Behaviors Some
animal behaviors are largely innate and
fixed (top), whereas others are largely
In Review
learned (bottom). This learning is a form
.
of cultural transmission.Top: Adapted from
Brain and behavior are linked, and behavioral disorders can be explained and possibly
The Beak of the Finch(p. 183), by J. Weiner,
1995, New York: Vintage. Bottom: Adapted from cured by understanding the brain. Understanding how the brain produces both behavior
“Cultural Transmission in the Black Rat: Pinecone and consciousness remains a major unanswered scientific question. Students of the brain
Feeding,” by J. Terkel, 1995, Advances in the
want to understand its place in the biological order of our planet. The brain consists of nearly
Study of Behavior, 24,p. 122.
symmetrical left and right cerebral hemispheres, each with a folded outer layer called the
cortex, which is divided into four lobes: temporal, frontal, parietal, and occipital. The brain
and spinal cord together make up the central nervous system. All the nerve fibers radiat-
ingout beyond the brain and spinal cord as well as all the neurons outside the brain and
spinal cord form the peripheral nervous system. Nerves of the PNS carry sensory information
to the CNS and motor instructions from the CNS to muscles and tissues of the body. A sim-
ple definition of behavior is any kind of movement in a living organism. Although all behav-
iors have both a cause and a function, they vary in complexity and in the degree to which
they are inherited, or automatic, and the degree to which they depend on learning.
PERSPECTIVES ON BRAIN AND BEHAVIOR
Returning to the central question in the study of brain and behavior,how the two are
related,we now describe three classic theories about the cause ofbehavior along with a
Visit the Brain and BehaviorWeb site major proponent of each school of thought—mentalism,dualism,and materialism—
(www.worthpublishers.com/kolb) as it relates to behavioral neuroscience. You will recognize familiar “common sense”
and go to the Chapter 1 Web links to view ideas that you might have about behavior as being derived from one or another ofthese
a timeline on the history of brain research. long-standing theories.
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WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 9
Aristotle and Mentalism York
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In classical mythology,Psyche was a mortal who became the wife of Art Res
the young god Cupid.Venus, Cupid’s mother, opposed his marriage g /
n
tsoibalem taosrktsa.l,and so she harassed Psyche with countless,almost impos- E. Lessi
Aristotle
(384–322 BC) Psyche performed the tasks with such dedication, intelligence,
and compassion that she was made immortal,thus removing Venus’s objection to her. François Gerard,
Psyche and Cupid(1798)
The ancient Greek philosopher Aristotle was alluding to this story when he suggested
that all human intellectual functions are produced by a person’s psyche.The psyche,
Aristotle argued, is responsible for life, and its departure from the body results in
death.
Aristotle’s account ofbehavior had no role for the brain,which he thought existed
to cool the blood.To him,the nonmaterial psyche was responsible for human thoughts, Psyche.Synonym for mind, an entity
perceptions, and emotions and for such processes as imagination, opinion, desire, once proposed to be the source of human
pleasure,pain,memory,and reason.The psyche was an entity independent ofthe body. behavior.
Aristotle’s view that a nonmaterial psyche governs our behavior was adopted by Chris- Mind.Proposed nonmaterial entity
tianity in its concept of the soul and has been widely disseminated throughout the responsible for intelligence, attention,
awareness, and consciousness.
world.
Mindis an Anglo-Saxon word for memory and,when “psyche”was translated into Mentalism. Of the mind; an explanation
of behavior as a function of the
English,it became mind.The philosophical position that a person’s mind,or psyche,
nonmaterial mind.
is responsible for behavior is called mentalism, meaning “of the mind.” Because
Mind–body problem. Quandary of
the mind is nonmaterial,it cannot be studied with scientific methods.Just the same,
explaining a nonmaterial mind in
mentalism has had an influence on modern behavioral science because many terms—
command of a material body.
sensation,perception,attention,imagination,emotion,motivation,memory,and volition
Dualism.Philosophical position that
among them—are still employed as labels for patterns of behavior today,and matters
holds that both a nonmaterial mind and
related to these behaviors are the focus ofcontemporary research in psychology.
the material body contribute to behavior.
Descartes and Dualism
In the first book on brain and behavior,Treatise on Man,René Des-
cartes (1596–1650), a French physiologist, mathematician, and phi-
losopher,proposed a new explanation ofbehavior in which the brain
played an important role. Descartes placed the seat of the mind in
thebrain and linked the mind to the body.He saw mind and body as
separate but interconnected.In the first sentence ofTreatise on Man
René Descartes
(1596–1650) (1664),he stated that mind and body “must be joined and united to
constitute people....”
To Descartes,most ofthe activities ofthe body and brain,including sensation,mo-
Figure 1-4
tion, digestion, breathing, and sleeping, could be explained by the mechanical and
physical principles current in seventeenth-century Europe. The mind, on the other Dualism Descartes argued that the
hand, is nonmaterial, separate from the body, and responsible for rational behavior. pineal body in the brain receives
different messages from a hand holding
Descartes’s proposal that an entity called the mind directs a machine called the body
a flute and from a hand touching a ball.
was the first serious attempt to explain the role of the brain in controlling intelligent
The mind, resident in the pineal body,
behavior.The problem of how a nonmaterial mind and a physical brain might inter-
interprets these messages and so learns
act has come to be called the mind–body problem,and the philosophical position that
about the flute and ball. From Treatise
behavior is controlled by two entities,a mind and a body,is called dualism.
on Man,by R. Descartes, 1664. Reprint and
Figure 1-4, an illustration from Treatise on Man, shows how, to Descartes, the
translation (p. 60), 1972, Cambridge, MA:
mind receives information from the body.When a hand touches a ball,for example,
Harvard University Press.
