Science Brain and Behavior

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1
What Are the Origins of Brainand Behavior?


Focus
on Disorders: Traumatic Brain Injury

Why Study Brain and Behavior?

Focus
on Disorders: Linking Brain Function to Brain
Injury
What
Isthe Brain?
Gross
Structure ofthe Nervous
System
What
Is
Behavior?


Perspectives on Brain and Behavior

Aristotle and Mentalism
Descartes
and Dualism
Focus
on New Research: The Origins
of
Spoken
Language

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.


Human Evolution

Humans: Members
ofthe Primate Order
Australopithecus: Our Distant
Ancestor
The First
Humans


Evolution of the Human Brain

Brain Size and Behavior
Why the Hominid Brain Enlarged

Studying Brain and Behavior in
Modern Humans

Fallacies
of
Human Brain-Size Comparisons
Culture
Focus
on Disorders: Learning Disabilities




I have met seems to go through this stage of narcissistic
preoccupation, which creates a necessary
shield to protect them from the painful realities of
the situation until they have a chance to heal.) I had
very little sense of anything beyond the material
world and could only write about things that could
be described in factual terms. I wrote, for example,
about my various impairments and how I learned to
compensate for them by a variety of methods.
At this point in my life, I began to involve myself
with other brain-damaged people. This came
about in part after the publication of my article. To
my surprise, it was reprinted in many different
publications, copied, and handed out to thousands
of survivors and families. It brought me an
enormous outpouring of letters, phone calls, and
personal visits that continue to this day. Many
were struggling as I had struggled, with no diagnosis,
no planning, no rehabilitation, and most of
all, no hope. . . . The catastrophic effect of my injury
was such that I was shattered and then remolded
by the experience, and I emerged from it
a profoundly different person with a different set
of convictions, values, and priorities. (Linge, 1990)
The diffuse effects of traumatic brain injury make diagnosis
very difficult, which is why brain injuries have been
Traumatic Brain Injury
Focus on Disorders
E ach year a reported 80,000 people in
the United States of America experience
long-term disability from complications
related to head trauma (Brain Injury
Association, 2002). Traumatic brain injuries
are the leading cause of both death
and disability among children and teenagers
(Cassidy et al., 2004). What is it like
to be brain injured? Fred Linge, a clinical
psychologist with a degree in brain
research, wrote this description 12 years
after his traumatic brain injury occurred:
In the second it took for my car to
crash head-on, my life was permanently
changed, and I became another
statistic in what has been called “the
silent epidemic.”
During the next months, my family and I
began to understand something of the reality of the
experience of head injury. I had begun the painful
task of recognizing and accepting my physical,
mental, and emotional deficits. I couldn’t taste or
smell. I couldn’t read even the simplest sentence
without forgetting the beginning before I got to the
end. I had a hair-trigger temper that could ignite instantly
into rage over the most trivial incident.
During the first year, I could not take too much
stimulation from other people. My brain would
simply overload, and I would have to go off into
my room to get away. Noise was hard for me to
take, and I wanted the place to be kept quiet,
which was an impossibility in a small house with
three youngsters in it. I remember laying down
some impossible rules for all of us. For example, I
made rules that everybody had to be in bed by
9:30 PM, that all lights had to be out, and that no
noise of any kind was permitted after that time. No
TV, radios, or talking was allowed. Eventually the
whole family was in an uproar.
Two years after my injury, I wrote a short article:
“What Does It Feel Like to Be Brain Damaged?”
At that time, I was still intensely focusing on myself
and my own struggle. (Every head-injured survivor
Direction of blow Direction of blow
A variety of mechanical
forces cause traumatic
brain injuries as a result
of a blow to the head.
Movement of the brain may shear nerve
fibers, causing microscopic lesions, especially
in frontal and temporal lobes. Blood trapped
in the skull (hematoma) and swelling (edema)
cause pressure on the brain.
The damage at the site of impact is
called a coup (shown in pink).
The pressure resulting from a coup
produce a countercoup on the
opposite side of the brain (shown
in blue).
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WHY STUDY BRAIN AND BEHAVIOR?
The brain is a physical object, a living tissue, a body organ. Behavior is action, momentarily
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.
brain injuries resulting from motor vehicle accidents are
particularly severe because the head is moving when the
blow is struck, thereby increasing the velocity of the impact.
In the years after his injury, Fred Linge made an immense
journey. Before the car crash, he gave less thought to
the relation between his brain and his behavior than he did
to tying his shoes. At the end of his journey, adapting to his
injured brain and behavior dominated his life. He became
a consultant and advisor to other people who also had suffered
brain injury.
The purpose of this book is to take you on a journey toward
understanding the link between brain and behavior:
how the brain is organized to create and monitor behavior
and what happens when the brain is not functioning properly.
Much of the evidence comes from studying three sources: the
evolution of brain and behavior in diverse animal species,
how the brain is related to behavior in normal people, and
changes in people who suffer brain damage or other brain abnormalities.
The knowledge emerging from the results of
these studies is changing how we think about ourselves, how
we structure education and our social interactions, and how
we aid those with brain injury, disease, and disorder.
In this chapter, we answer the question, What are the
origins of brain and behavior? We begin by defining both
brain and behavior and outlining the nervous system’s basic
structure. We then take a historical look at three major theories
concerning the relation between brain and behavior.
From this background, we explore the evolution of brain
and behavior, showing how the brain and complex behavior
emerged and changed as animals evolved. Finally, we consider
how the human brain has adapted to its most complex
function—culture.
collectively called a “silent epidemic.” Victims of severe
traumatic brain injury can suffer serious repercussions in
their everyday lives. Like Fred Linge, many have difficulty
returning to their former levels of functioning, including
carrying out the jobs that they held before injury.
Traumatic brain injury results from a blow to the head
that subjects the brain to a variety of forces shown on the
accompanying illustration:
The force exerted on the skull at the site of the blow
causes a contusion (bruising) known as a “coup” (French
for a strike or blow).
The blow may force the brain against the opposite side
of the skull, producing an additional contusion called a
“countercoup.”
The movement of the brain may cause a twisting or
shearing of nerve fibers, resulting in microscopic lesions
(damage to the nervous system). Such lesions may be found
throughout the brain, but they are most common at the
front and sides.
The bruises and strains caused by the impact may produce
bleeding (hemorrhage). The blood trapped within the
skull acts as a growing mass (hematoma), which exerts pressure
on surrounding brain regions.
Like blows to other parts of the body, blows to the
brain produce edema (swelling), a collection of fluid in and
around damaged tissue. Edema is another source of pressure
on the brain.
People who sustain traumatic brain injury often lose
consciousness because the injury affects nerve fibers in
lower parts of the brain associated with waking. The severity
of coma can indicate the severity of the injury. Traumatic
2 ! CHAPTER 1
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WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 3
Linking Brain Function to Brain Injury
Focus on Disorders
The case history of Phineas Gage is a source of early insight
into how the brain controls behavior (MacMillan, 2000).
Gage was a 25-year-old dynamite worker on a railroad bed
construction site who in 1848 survived an explosion that
blasted an iron tamping bar (about a meter long and 3 centimeters
wide) through the front of his head (see photograph).
Surprisingly, quite a few people have survived similar
injuries, even from tamping bars, but Gage’s physician, John
M. Harlow, wrote an account of Gage’s accident and this account
helped propel Gage to fame.
Gage had been of average intelligence and very industrious
and dependable. He was described as “energetic and
persistent in executing all of his plans of operation.” But,
after the accident, his behavior changed completely. Harlow,
in describing the case, wrote:
The equilibrium or balance, so to speak, between
his intellectual faculties and animal propensities
seems to have been destroyed. He is fitful, irreverent,
indulging at times in the grossest profanity,
manifesting but little deference to his fellows,
impatient of restraint or advice when it conflicts
with his desires, at times perniciously obstinate, yet
capricious and vacillating, devising many plans of
operation, which are no sooner arranged than they
are abandoned in turn for others appearing more
feasible. A child in his intellectual capacity and
manifestations, he has the animal passions of a
strong man. (Blumer and Benson, 1975, p. 153)
The remarkable feature of Gage’s frontal-lobe injury is
that he did not display obvious motor or memory impairments;
his brain injury mainly affected his personality. Harlow
provided evidence that the frontal lobes were locations
of foresight and planning.
Although the tamping bar and Gage’s skull have been
preserved, Gage’s precise injury could not be described, because
no autopsy was performed after his death and so the
actual damage produced by the tamping bar could not be determined.
Measurements from Gage’s skull and modern imaging
techniques have been used to reconstruct the accident
and determine the probable location of the lesion. The frontal
cortex of both hemispheres appears to have been damaged.
Reconstruction of Gage’s brain injury with the use of modern
imaging techniques. From “The Return of Phineas Gage: Clues about the
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.
Department of Neurology and Image
Analysis Facility, University of Iowa.
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 patients who
died of brain diseases and related their symptoms to their pathology, the accumulated
research suggests three reasons for linking the study of brain 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 different
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 evolution
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 example,
in Chapters 13 and 14, we address questions related to how we learn and how
we think.
None of us 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
Index of Disorders Discussed in Chapters 1 through 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.
Phenylketonuria 15
Posttraumatic stress disorder 7
Presbyopia 8*
Psychosis 7
Quadripelegia 10
Restless legs syndrome 12
Schizophrenia 5, 6*, 7, 15
Scotoma 8
Seasonal affective disorder 12*
Sleep apnea 12*
Spinal-cord injury 10, 11
Split-brain syndrome 14
Stroke 2*, 15
Synesthesia 14*
Tay-Sachs disease 3
Tourette’s syndrome 5, 10*
Traumatic brain injury 1*, 15
Insomnia 12
Korsakoff’s syndrome 13*
Learning disabilities 1*, 6
Lou Gehrig’s disease 4*
Mania 15
Meningitis 2*
Mental retardation 6
Migraine 8*
Missile wound 1
MPTP poisoning 5*
Multiple sclerosis 3*, 15
Myasthenia gravis 4*
Myopia 8*
Narcolepsy 12
Obesity 11
Obsessive compulsive
disorder 5, 7
Panic disorder 11*
Paraplegia 10*
Parkinson’s disease 5*, 15
Brain tumors 3*
Carbon monoxide poisoning 8*
Cerebral aneurysm 9*
Cerebral palsy 6*, 10
Closed head injury 1*
Contralateral neglect 14
Dementia 15
Demoic acid poisoning 7
Depression 5, 7, 11*, 15
Down’s syndrome 3
Drug-induced psychosis 7*
Encephalitis 2*
Environmental deprivation 6*
Epilepsy 4, 9*, 15
Fetal alcohol syndrome 7*
Frontal leucotomy 11
Hemianopia 8
Huntington’s chorea 3*
Hyperopia 8*
Insanity 1*
Addiction 7
ADHD 15
Affective disorders 11*, 15
Agenesis of the frontal lobe 11*
Agnosia 8
Alzheimer’s disease 5, 13*, 15
Amnesia 13
Androgen insensitivity syndrome 11*
Androgenital syndrome 11*
Anencephaly 6
Anorexia nervosa 11
Anxiety disorders 11*, 15
Aphasia 9
Apraxia 10
Arteriovenous malformations 9*
Asperger’s syndrome 15
Ataxia 8
Autism 10*
Bell’s palsy 2*
Bipolar disorder 15
Table 1-1
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between brain and behavior, she had insight into the disorders of many of her clients
and treatment options for them. So let’s begin, by defining first the brain, then behavior,
and finally how they evolved together.
What Is the Brain?
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 communicate
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 of what
“brain”means.
Brain is the Anglo-Saxon word for the tissue that is found within the skull, and it
is this tissue that Harvey wanted to put into a bottle. The brain has two almost symmetrical
halves called hemispheres, one on the left and one on the right. So, just as
your body is symmetrical, having two arms and two legs, so is the brain. Figure 1-1A
shows the left hemisphere of a typical human brain oriented in the upright human
skull. If you 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
tissue, the cerebral cortex, detailed in the sectional view in Figure 1-1A. The word cortex,
Latin for the bark of a tree, is apt, considering the cortex’s heavily folded surface
and its location in covering most of the rest of the brain. The grooves of the cortex are
called sulci and the bumps are called gyri. Unlike the bark on a tree, they are not random
folds but demark functional zones. Later on, we’ll provide their names and functions.
The cortex of each hemisphere is divided into four lobes, named after the skull
bones beneath which they lie.
WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 5
Frontal
lobe
Parietal
lobe
Temporal
lobe
Occipital
lobe
Sectional view
Bumps in the brain's
folded surface are
called gyri, and cracks
are called sulci.
Front
Bottom
Top
Your right hand, if made into a
fist, represents the positions of
the lobes of the left hemisphere
of your brain.
Temporal lobe
(thumb)
Frontal lobe
(fingers)
Parietal lobe
(knuckles)
Occipital lobe
(wrist)
Lobes define broad
divisions of the
cerebral cortex.
(A) (B)
The brain is made up
of two hemispheres,
left and right.
Cerebral cortex
is the brain’s
thin outer
“bark” layer.
Back
Figure 1-1
The Human Brain (A) The cerebral
cortex of the nearly symmetrical
hemispheres of the brain is divided into
four lobes. The cerebral cortex is a thin
sheet of nerve tissue that is folded many
times to fit inside the skull, as shown in
the sectional view. (B) Your right fist can
serve as a guide to the orientation of
the brain’s left hemispheres and lobes.
Glauberman/Photo Researchers
Hemisphere. Literally, half a sphere,
referring to one side of the cerebral cortex
or one side of the cerebellum.
Cerebral cortex. Outer layer of braintissue
surface composed of neurons; the
human cerebral cortex contains many
folds.
On the Foundations of Behavioral
Neuroscience CD, visit the module on the
central nervous system. Go to the overview
and look at the three-dimensional view of
the human cortex for a hands-on view of
what this organ looks like. (See the Preface
for information about this CD.)
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The forward-pointing temporal lobe is located at the side of the brain, approximately
the same place as the thumb on your upraised fist. Immediately above your
thumbnail, your fingers correspond to the location of the frontal lobe, so called because
it is located at the front of the brain, beneath the frontal bone of the skull. The
parietal lobe is located beneath the parietal bone at the top of the skull, behind the
frontal lobe and above the temporal lobe. The area at the back of each hemisphere beneath
the occipital bone constitutes the occipital lobe.
Harvey clearly wanted to preserve not just his brain but his self—his consciousness,
his thoughts, his intelligence. This meaning of the term brain refers to something
other than the organ found inside the skull. It refers to the brain as that which exerts
control over behavior.
This meaning of brain is what we intend when we talk of someone being “the
brain” or when we speak of the computer that guides a spacecraft as being the vessel’s
“brain.” The term brain, then, signifies both the organ itself and the fact that this organ
controls behavior.Why could Harvey not manage to preserve his control-exerting self
inside a bottle? Read on to learn one answer to this question.
Gross Structure of the Nervous System
Just like every other organ of the body, the brain is composed of billions of cells that
come in a variety of shapes and sizes. One type of brain cell is the neuron (sometimes
called nerve cell), and neurons are the cells that most directly control behavior. Neurons
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
body organs.
The nervous system consists of two main subdivisions: the central nervous system
and the peripheral nervous system.Most of the connections between the brain and the
rest of the body are made through the spinal cord, which descends through a canal
in the backbone. Together, the brain and spinal cord make up the central nervous system
(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 located
as the core of the nervous system and because it is the core structure mediating
behavior.
All the nerve processes radiating out beyond the brain and spinal cord as well as
all the neurons outside the brain and spinal cord constitute the peripheral nervous
system (PNS). An extensive network of sensory neurons in the PNS connect to receptors
on the body’s surface, internal organs, and muscles to gather sensory information
for the CNS. Motor neurons in the PNS convey information from the CNS to move
muscles of the face, body, and limbs.Motor neurons also govern the workings of your
body’s internal organs, autonomic functions, such as the beating of your heart, the contractions
of your stomach, and the movement of your 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 if our muscles
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
6 ! CHAPTER 1
Use the Foundations CD to look at
how these nerve networks work in our
brains. The overview of the brain in the
central nervous system module includes a
rotatable, three-dimensional view of the
brain that will help you visualize how all
these parts fit together.
Temporal lobe. Cortex lying below the
lateral fissure, beneath the temporal bone
at the side of the skull.
Frontal lobe. Cerebral cortex anterior to
the central sulcus and beneath the frontal
bone of the skull.
Parietal lobe. Cerebral cortex posterior
to the central sulcus and beneath the
parietal bone at the top of the skull.
Occipital lobe. Cerebral cortex at the
back of the brain and beneath the
occipital bone.
Neuron. A brain cell engaged in
information processing.
Spinal cord. Part of the central nervous
system encased within the vertebrae or
spinal column.
Central nervous system (CNS). The
brain and spinal cord.
Peripheral nervous system (PNS). All
the neurons in the body located outside
the brain and spinal cord.
Sensory neuron. Neuron that carries
incoming information from sensory
receptors into the spinal cord and brain.
Motor neuron. Neuron that carries
information from the spinal cord and
brain to make muscles contract.
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movements related to our thoughts. The muscles of the larynx
subliminally move when we “think in words,” for instance, and
we make subliminal movements of our eyes when we imagine
or visualize a scene. So, in Jacobson’s experiment, people practiced
“total” relaxation and were later asked what the experience
was like. They reported a condition of “mental emptiness,” as if
the brain had gone blank.
In 1957,Woodburn Heron investigated the effects of sensory
deprivation, including feedback from movement, by having
each subject lie on a bed in a bare, soundproof room and
remain completely still. Tubes covered the subjects’ arms so
that they had no sense of touch, and translucent goggles cut
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 situation.
Some subjects even hallucinated, as if their brains were
somehow trying to create the sensory experiences that they
suddenly lacked. Most asked to be released from the study before
it ended.
Findings from these experiments suggest that the CNS
needs ongoing sensory stimulation, including the stimulation
that comes from movement, if it is to maintain its intelligent activity.
Thus, when we use the term brain to mean an intelligent,
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 of Behavior, published
in 1970, with the following definition: “Behavior consists of patterns in time.” These
patterns can be made up of movements, 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 of a 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 is exquisitely evolved to
eat certain kinds of pine cones. When eating these pine cones, crossbills use largely
WHAT ARE THE ORIGINS OF BRAIN AND BEHAVIOR? ! 7
Central nervous system (CNS)
The brain and spinal cord, those parts of the
nervous system that are encased by the skull and
vertebrate bones
Peripheral nervous system (PNS)
Neurons and nerve processes outside CNS
Sensory and motor
connections to internal
body organs
Sensory connections
to receptors in the
skin
Motor connections
to body muscles
Figure 1-2
Gross Structure of the Human Nervous
System In essence, the nervous system
interprets sensory stimulation and
produces behavior.
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fixed behavioral patterns that are inherited and do not require much modification
through learning.
If the shape of a crossbill’s beak is changed even slightly by trimming, the bird is
no longer able to eat preferred pine cones until its beak grows back. Roof rats, in contrast,
are rodents with sharp incisor teeth that appear to have evolved to cut into anything.
But roof rats can eat pine cones efficiently only if they 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 system
produces each type of behavior.
The complexity of behavior varies considerably in different species. Generally, animals
with smaller, simpler nervous systems have a narrow range of behaviors.Animals
with complex nervous systems have more behavioral options.We humans believe that
we are the animal species with the most complex nervous system and the greatest capacity
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 depends
mostly on learning, we, like other species, still possess many inherited ways of
responding. The sucking response of a newborn infant is an inherited eating pattern in
humans, for example.
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 of behavior along with a
major proponent of each school of thought—mentalism, dualism, and materialism—
as it relates to behavioral neuroscience. You will recognize familiar “common sense”
ideas that you might have about behavior as being derived from one or another of these
long-standing theories.
In Review .
Brain and behavior are linked, and behavioral disorders can be explained and possibly
cured by understanding the brain. Understanding how the brain produces both behavior
and consciousness remains a major unanswered scientific question. Students of the brain
want to understand its place in the biological order of our planet. The brain consists of nearly
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 radiating
out 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 simple
definition of behavior is any kind of movement in a living organism. Although all behaviors
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.
8 ! CHAPTER 1
Visit the Brain and Behavior Web site
(www.worthpublishers.com/kolb)
and go to the Chapter 1 Web links to view
a timeline on the history of brain research.
A crossbill's beak is
specifically designed to
open pine cones. This
behavior is innate.
A baby roof rat must
learn from its mother
how to eat pine cones.
This behavior is learned.
Figure 1-3
Innate and Learned Behaviors Some
animal behaviors are largely innate and
fixed (top), whereas others are largely
learned (bottom). This learning is a form
of cultural transmission.Top: Adapted from
The Beak of the Finch (p. 183), by J. Weiner,
1995, New York: Vintage. Bottom: Adapted from
“Cultural Transmission in the Black Rat: Pinecone
Feeding,” by J. Terkel, 1995, Advances in the
Study of Behavior, 24, p. 122.
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