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Background to the Study of Psychology
“Know thyself.” These two words were inscribed on the shrine of the Oracle of Apollo, at Delphi, Greece, in
the sixth century b.c. Throughout recorded history, human beings have striven to understand the nature of
being human, to fathom the mysteries of the human mind and human behavior. Today that endeavor is pursued
as a science, the science of psychology. In this first, background unit, we examine some fundamental ideas
that helped to bring about a science of psychology, and we preview some of the methods that help to make
psychology a science.
Foundations for the Study of Psychology
Three Foundation Ideas for
Psychology: A Historical
The Idea of Physical Causation of
T he human being, as far as any human being can tell, is
the only creature that contemplates itself. We not only
think, feel, dream, and act but also wonder how and
why we do these things. Such contemplation has taken many
forms, ranging from just plain wondering to folk tales and pop-
The Idea That the Mind and Behavior ular songs, to poetry and literature, to formal theologies and
Are Shaped by Experience
philosophies. A little more than a century ago, human self-
The Idea That the Machinery of
Behavior and Mind Evolved contemplation took a scientific turn, and we call that science
Through Natural Selection psychology.
Welcome! Welcome to Psychology and to psychology—that is,
The Scope of Psychology to this book and to the field of study it is about. I hope you will
Varieties of Explanations in enjoy them both. The big question of psychology is one of the
Psychology, and Their Application
to Sexual Jealousy most fascinating that anyone can ask: What makes people feel,
The Connections of Psychology to think, and behave the way they do? In this book you will read
Other Scholarly Fields about many routes toward answering that big question, and you
Psychology as a Profession will discover many dozens of specific findings and ideas that
help to answer it.
Thoughts About Using This Book It is useful to begin with a formal definition of our subject:
and Its Special Features Psychology is the science of behavior and the mind. In this defi-
nition behavior refers to the observable actions of a person or
an animal. Mind refers to an individual’s sensations, percep-
tions, memories, thoughts, dreams, motives, emotional feel-
ings, and other subjective experiences. It also refers to all of the
unconscious knowledge and operating rules that are built into
or stored in the brain, and that provide the foundation for or-
ganizing behavior and conscious experience. Science refers to
all attempts to answer questions through the systematic collec-
tion and logical analysis of objectively observable data. Most of
the data in psychology are based on observations of behavior,
because behavior is directly observable and mind is not; but
psychologists often use those data to make inferences about the
In this opening chapter, I want to do three things, all aimed
at helping to prepare you for the rest of the book. First, I want
to present you with a little bit of the history and philosophy
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2 PART 1 ■ BACKGROU ND TO THE STU DY OF PSYCHOLOGY
that predate and underlie modern psychology. More specifically, I will say some-
thing about the historical origins of three ideas that are so basic to our science that
I refer to them as “foundation ideas for psychology.” Second, I want to tell you
something about the scope of modern psychology, especially about the various lev-
els of analysis that psychologists use in learning about and explaining mental expe-
riences and behavior. Third, I want to tell you something about the features of this
book and how you might use them to maximize your enjoyment of it and your
learning from it. I put that section last, because I thought you might learn more
from it after you have read a bit into the book than you would if it came first. If you
prefer to read that section first, please do. It starts on page 19.
1 <<< There is one feature of the book that I want you to notice right now, however. In
How might the focus questions (such as the margins of the text, throughout the book, you will find numbered focus questions.
this one) in the text’s margins be used to The first such question appears in the margin next to the paragraph you are reading
guide initial reading and review?
right now. These are the questions that I am trying to answer in the text, and they
are also good test questions. An effective way to study this book is to read and think
about each focus question, as you come to it, before you read the adjacent paragraphs
of text, which are aimed at answering that question. This method of study will help
you focus your attention on the text and understand and remember what you read.
If you read with the active intention of answering the focus questions, your mind is
less likely to drift, and you are more likely to understand and think about what you
read than if you read passively just to “learn” or “absorb” the material.
Three Foundation Ideas for Psychology:
A Historical Overview
The founding of psychology as a formal, recognized, scientific discipline is com-
monly dated to 1879, when Wilhelm Wundt, in Germany, opened the first
university-based psychology laboratory. At about that same time, Wundt also au-
thored the first textbook of psychology and began mentoring the first official grad-
uate students of psychology. The first people to earn Ph.D. degrees in psychology
were Wundt’s students.
But the roots of psychology predate Wundt. They were developed by people
who called themselves philosophers, physicists, physiologists, and naturalists. In
this section we shall examine three fundamental ideas of psychology, all of which
were conceived of and debated before the establishment of psychology as a recog-
René Descartes Descartes’s specula-
tions, in the seventeenth century, nized scientific discipline. Briefly, the ideas are these:
about reflexes and the interaction of 1. Behavior and mental experiences have physical causes, so they are amenable
the body and soul in controlling volun- to scientific analysis.
tary actions were an important step
toward a scientific analysis of human 2. The way a person behaves, thinks, and feels is modified, over time, by the per-
behavior. son’s experiences in his or her environment.
3. The body’s machinery, which produces behavior and mental experiences, is a
product of evolution by natural selection.
The Idea of Physical Causation of Behavior
Before a science of psychology could emerge, people had to conceive of and accept
the idea that questions about human behavior and the mind can, in principle, be
answered scientifically. Seeds for this conception can be found in the writings of
some of the ancient Greeks, who speculated about the senses, the human intellect,
and the physical basis of the mind in ways that seem remarkably modern. But such
ideas became dormant in the Middle Ages and did not begin to sprout again until
the fifteenth century (the Renaissance) or to take firm hold until the eighteenth
century (the Enlightenment).
Philosophy was tightly bound to religion through the seventeenth century. The
church maintained that each human being consists of two distinct but intimately
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CHAPTER 1 ■ FOU N DATIONS FOR TH E STU DY OF PSYCHOLOGY 3
conjoined entities, a material body and an immaterial soul—a view referred to
today as dualism. The body is part of the natural world and can be studied scientif-
ically, just as inanimate matter can be studied. The soul, in contrast, is a supernat-
ural entity that operates according to its own free will, not natural law, and
therefore cannot be studied scientifically. This was the accepted religious doctrine,
which—at least in most of Europe—could not be challenged publicly without risk
of a charge of heresy and consequent execution. Yet the doctrine left some room
for play, and one who played dangerously near the limits was the great French
mathematician, physiologist, and philosopher René Descartes (1596–1650).
Descartes’s Version of Dualism: Focus on the Body
Prior to Descartes, most dualists assigned all the interesting qualities of the human >>> 2
being to the soul. The soul was deemed responsible for the body’s heat, for its abil- What was Descartes’s version of dualism?
ity to move, for life itself. In Treatise of Man (1637/1972), and even more explicitly How did it help pave the way for a science
in The Passions of the Soul (1649/1985), Descartes challenged this view. He had per-
formed dissections of animals and of human cadavers, was familiar with research
on the flow of blood, and began to regard the body as an intricate, complex machine
that generates its own heat and is capable | figure 1.1 | Descartes’s depic-
of moving even without the influence of tion of a reflex Descartes believed
the soul. Although little was known about that reflexes occur through purely
the nervous system in his time, Descartes’s mechanical means. In describing this
figure, Descartes (1637/1972) suggest-
conception of the mechanical control of
ed that the fire causes movement in
movement resembles our modern under- the nearby particles of skin, pulling on
standing of reflexes, which are involuntary a “thread” (that runs “C” to “C” along
responses to stimuli (see Figure 1.1). the back) going to the brain, which, in
Descartes believed that even quite com- turn, causes a pore to open in the
plex behaviors can occur through purely brain, allowing fluid to flow through a
mechanical means, without involvement “small conduit’’ to the muscles that
withdraw the foot. What Descartes
of the soul. Consistent with church doc-
called a “thread’’ and a “small conduit’’
trine, he contended that non-human ani- are today called nerves, and we now
mals do not have souls, and he pointed out know that nerves operate through
a logical implication of this belief: Any ac- electrical means, not through physical
tivity performed by humans that is qualita- pulling or the shunting of fluids.
tively no different from the behavior of a non-human animal can, in theory, occur
without the soul. If my dog (who can do some wondrous things) is just a machine,
then a good deal of what I do might occur purely mechanically as well.
In Descartes’s view, the one essential ability that I have but my dog does not is
thought, which Descartes defined as conscious deliberation and judgment. Whereas
previous philosophers ascribed many functions to the soul, Descartes ascribed just
one—thought. But even in his discussion of thought, Descartes tended to focus on
the body’s machinery. To be useful, thought must be responsive to the sensory
input channeled into the body through the eyes, ears, and other sense organs, and
it must be capable of directing the body’s movements by acting on the muscles.
How can the thinking soul interact with the physical machine—the sense or-
gans, muscles, and other parts of the body? Descartes suggested that the soul,
though not physical, acts on the body at a particular physical location. Its place of
action is a small organ (now known as the pineal body) buried between the two
hemispheres (halves) of the brain (see Figure 1.2). Threadlike structures, which
we now call nerves, bring sensory information by physical means into the brain,
where the soul receives the information and, by non-physical means, thinks about
it. On the basis of those thoughts, the soul then wills movements to occur and exe-
cutes its will by triggering physical actions in nerves that, in turn, act on muscles.
Descartes’s dualism, with its heavy emphasis on the body, certainly helped >>> 3
open the door for a science of psychology. It is a popular theory among non- Why was Descartes’s theory, despite its
scientists even today, because it acknowledges the roles of sense organs, nerves, intuitive appeal, unsuitable for a complete
and muscles in behavior without violating people’s religious beliefs or intuitive
feelings that conscious thought occurs on a non-physical plane. But the theory has
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4 PART 1 ■ BACKGROU ND TO THE STU DY OF PSYCHOLOGY
serious limitations, both as a philosophy and as a foundation for a
science of psychology. As a philosophy, it stumbles on the ques-
tion of how a non-material entity (the soul) can have a material ef-
fect (movement of the body), or how the body can follow natural
Cambridge, MA: Harvard University Press.
law and yet be moved by a soul that does not (Campbell, 1970). As
Descartes, R. (1972). Treatise of Man.
a foundation for psychology, the theory sets strict limits, which
few psychologists would accept today, on what can and cannot be
understood scientifically. The whole realm of thought and all be-
haviors that are guided by thought are out of bounds for scientific
analysis if they are the products of a willful soul.
Thomas Hobbes and the Philosophy of Materialism
At about the same time that Descartes was developing his
machine-oriented version of dualism, an English philosopher
| figure 1.2 | Descartes’s depiction of how the soul named Thomas Hobbes (1588–1679) was going much further. It
receives information through the eyes Descartes
should be no surprise that an Englishman, not a Frenchman, was
believed that the human soul is housed in the pineal gland,
depicted here as the tear-shaped structure in the center of first to break from dualism entirely. The church and state were
the head. In describing this figure, Descartes (1637/1972) constantly feuding in seventeenth-century England, and inklings
suggested that light from the arrow enters the eyes and of democracy were emerging. Hobbes had been employed as a
opens pores in structures that we now know as the optic tutor to the future King Charles II and, when the latter came to
nerves. Fluid flows from the eyes through the opened power, enjoyed royal protection. When a committee of bishops pe-
pores, causing movement in the pineal gland, which, in titioned that Hobbes be burned to death for his blasphemous book
Descartes’s words, “renders the idea’’ of the arrow to the
Leviathan, Hobbes received instead a stern warning (Hunt, 1993).
The church burned copies of his book, but Hobbes, promising not
to repeat his heresy, lived to the ripe age of 91.
4 <<< In Leviathan, and in a shorter work called Human Nature, Hobbes argued that
How did Hobbes’s materialism help lay the spirit, or soul, is a meaningless concept and that nothing exists but matter and en-
groundwork for a science of psychology? ergy, a philosophy now known as materialism. In Hobbes’s view, all human be-
havior, including the seemingly voluntary choices we make, can in theory be
understood in terms of physical processes in the body, especially the brain.
Conscious thought, he maintained, is purely a product of the brain’s machinery
and therefore subject to natural law. With this philosophy there is no theoretical
limit to what psychologists might study scientifically. Most of Hobbes’s work was
directed toward the implications of materialism for politics and government, but
his ideas helped inspire, in England, a school of thought about the mind known as
empiricism, to which we shall soon turn.
Nineteenth-Century Physiology: Learning About the Machine
The idea that the body, including the brain, is a machine, amenable to scientific
study, helped to promote the science of physiology—the study of the body’s ma-
chinery. By the beginning of the nineteenth century, considerable progress had been
made in this endeavor, and during that century discoveries were made about the
nervous system that contributed significantly to the origins of scientific psychology.
Increased Understanding of Reflexes One especially important development
for the later emergence of psychology was an increased understanding of reflexes.
The basic arrangement of the nervous system—consisting of a central nervous sys-
tem (brain and spinal cord) and peripheral nerves that connect the central nervous
A seventeenth-century mechanical man Mechanical clocks
represented the pinnacle of technological achievement of the
seventeenth century, comparable to computers today. For
amusement, clocklike mechanisms were used to operate
robotic, humanoid figures, as illustrated here. Such mechanical
men helped to inspire, in Descartes and Hobbes, the idea that
actual human beings might also operate by mechanical means,
not requiring a nonmaterial spirit to move them.
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CHAPTER 1 ■ FOU N DATIONS FOR TH E STU DY OF PSYCHOLOGY 5
system to sense organs and muscles—was well understood by the beginning of the >>> 5
nineteenth century. In 1822 in France, François Magendie demonstrated that How did the nineteenth-century under-
nerves entering the spinal cord contain two separate pathways: one for carrying standing of the nervous system inspire a
theory of behavior called reflexology?
messages into the central nervous system from the skin’s sensory receptors and
one for carrying messages out to operate muscles. Through experiments with ani-
mals, scientists began to learn about the neural connections that underlie simple
reflexes, such as the automatic withdrawal response to a pin prick, and found brain
areas that, when active, could either enhance or inhibit such reflexes.
Some of these physiologists began to suggest that all human behavior occurs
through reflexes, that even so-called voluntary actions are actually complex re-
flexes involving higher parts of the brain. One of the most eloquent proponents of
this view, known as reflexology, was the Russian physiologist I. M. Sechenov. In his
monograph Reflexes of the Brain, Sechenov (1863/1935) argued that every human
action, “[b]e it a child laughing at the sight of toys, or . . . Newton enunciating
universal laws and writing them on paper,” can in theory be understood as a reflex.
All human actions, he claimed, are initiated by stimuli in the environment. The
stimuli act on a person’s sensory receptors, setting in motion a chain of events in
the nervous system that culminates in the muscle movements that constitute the
action. Sechenov’s work inspired another Russian physiologist, Ivan Pavlov
(1849–1936), whose work on reflexes played a critical role in the development, in
North America, of a school of thought in psychology called behaviorism (discussed
in Chapter 4).
The Concept of Localization of Function in the Brain Another important ad- >>> 6
vance in nineteenth-century physiology was the concept of localization of function How did discoveries of localization of func-
in the brain, the idea that specific parts of the brain serve specific functions in the tion in the brain help establish the idea
that the mind can be studied scientifically?
production of mental experience and behavior. In Germany, Johannes Müller
(1838/1965) proposed that the different qualities of sensory experience come
about because the nerves from different sense organs excite different parts of the
brain. Thus we experience vision when one part of the brain is active, hearing
when another part is active, and so on. In France, Pierre Flourens (1824/1965) per-
formed experiments with animals showing that damage to different parts of the
brain produces different kinds of deficits in animals’ ability to move. And Paul
Broca (1861/1965), also in France, published evidence that people who suffer in-
jury to a very specific area of the brain’s left hemisphere lose the ability to speak
but do not lose other mental abilities. All such evidence about the relationships be-
tween mind and brain helped lay the groundwork for a scientific psychology, be-
cause it gave substance to the idea of a material basis for mental processes.
Early evidence for localization of
function Shown here is the pre-
served brain of Paul Broca’s patient
known as Tan, who lost his ability to
speak after suffering brain damage.
The damage is in the left frontal lobe,
in an area now called Broca’s area
(discussed in Chapter 5).
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the study of the effects of experience on one’s thoughts, feelings, and behavior. As
examples, social psychologists study the ways in which people are influenced by
their social environment; cultural psychologists study differences among people
that arise from growing up in different cultures; developmental psychologists are
interested in the experiences that lead children to acquire language and to think in
ever more complex ways; clinical psychologists are interested in the experiences
that can lead to mental disorders or can help one overcome such disorders; and
cognitive psychologists strive to understand the mental machinery that makes
learning and memory possible. The impact of empiricist philosophy on psychology
has been enormous.
The Nativist Response to Empiricism
For every philosophy that contains part of the truth, there is an opposite philoso-
phy that contains another part of it. The opposite of empiricism is nativism, the
view that some knowledge and rules of operation are native to the human mind—
that is, are inborn and do not have to be acquired from experience.
Take a sheet of white paper and present it with all the learning experiences that >>> 9
a normal human child might encounter (a suggestion made by Ornstein, 1991). Why is the ability to learn dependent on
The paper will learn nothing. Talk to it, sing to it, give it apples and oranges, take it inborn knowledge? In Kant’s nativist phi-
losophy, what is the distinction between
for trips in the country, hug it and kiss it; it will learn nothing about language, a priori knowledge and a posteriori
music, fruit, nature, or love. To learn anything, any entity must contain some ini- knowledge?
tial machinery, already built into it. At a minimum, that machinery must include
an ability to sense some aspects of the environment, some means of interpreting
and recording those sensations, some rules for storing and combining those sen-
sory records, and some rules for recalling them when needed. The mind, contrary
to Locke’s poetic assertion, must come with some initial furnishings in order for it
to be furnished further through experience.
While empiricist philosophy flourished in England, nativist philosophy took root
in Germany, led by such thinkers as Gottfried Wilhelm von Leibniz (1646–1716)
and Immanuel Kant (1724–1804). In his Critique of Pure Reason (1781/1908), Kant
distinguished between a priori knowledge, which is built into the human brain and
does not have to be learned, and a posteriori knowledge, which one gains from
experience in the environment. Without the first, a person could not acquire the
second. As an illustration, Kant referred to a child’s learn-
ing of language. The specific words and grammar that the
child acquires are a posteriori knowledge, but the child’s
ability to learn a language at all depends on a priori knowl-
edge. The latter includes built-in rules about what to attend
to and how to store and organize the verbal sounds that are
heard in ways that allow the child eventually to make sense
of them. Kant also argued that to make any sense of the
physical world, the child must already have, built into its
mind, certain fundamental physical concepts, such as the
concepts of space and time. Without such concepts, a child
would have no capacity for seeing an apple as spherical or Alan Decker / University of California, San Diego
for detecting the temporal contiguity of two events.
A fun robot that can learn This computer-driven robot,
designed by researchers at the University of California,
San Diego, can keep track of some of its previous inter-
actions with children and incorporate them into its future
responses to the children. Such machines can learn only
the kinds of information that they are programmed to
learn. Similarly, according to nativist philosophers, human
learning is limited by the information and operating rules
that are genetically programmed into the human brain.
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8 PART 1 ■ BACKGROU ND TO THE STU DY OF PSYCHOLOGY
The Idea That the Machinery of Behavior and Mind
Evolved Through Natural Selection
Kant understood that the human mind has some innate furnishings, but he had no
scientific explanation of how those furnishings could have been built or why they
function as they do. That understanding came, at last, in 1859, when the English
naturalist Charles Darwin (1809–1882) published The Origin of Species, a book that
was destined to revolutionize biology, mark a new age in philosophy, and provide,
along with the developments in physiology, a biological grounding for psychology.
Natural Selection and the Analysis of the Functions of Behavior
10 <<< Darwin’s fundamental idea (explained much more fully in Chapter 3) was that
How did Darwin’s theory of natural selection living things evolve gradually, over generations, by a process of natural selection.
offer a scientific foundation for explaining Those individuals whose inherited characteristics are well adapted to their envi-
behavior by describing its functions? How
did it provide a basis for understanding
ronment are more likely to survive and reproduce than are other individuals. At
the origin of a priori knowledge? each generation, random changes in the hereditary material produce variations in
offspring, and those variations that improve the chance of survival and reproduc-
tion are passed from generation to generation in increasing numbers.
Because of natural selection, species of plants and animals change gradually
over time in ways that allow them to meet the changing demands of their environ-
ments. Because of evolution, the innate characteristics of any given species of
plant or animal can be examined for the functions they serve in allowing individu-
als to survive and reproduce. To understand, for example, why finches have stout
beaks and warblers have slender beaks, one must know what foods the birds eat
and how they use their beaks to obtain those foods. The same principle that applies
to anatomy applies to behavior. Through natural selection, living things have ac-
quired instinctive tendencies to behave in ways that promote their survival and re-
production. A key word here is function. While physiologists were examining the
neural mechanisms of behavior, and empiricist philosophers were analyzing law-
ful relationships between behavior and the environment, Darwin was studying the
functions of behavior—the ways in which an organism’s behavior helps it to sur-
vive and reproduce.
Application of Darwin’s Ideas to Psychology
In The Origin of Species, Darwin discussed only plants and non-human animals, but
in later writings he made it clear that he viewed humans as no exception. We hu-
mans also evolved through natural selection, and our anatomy and behavior can be
analyzed in the same ways as can those of other living things.
In a book entitled The Expression of the Emotions in Man and Animals, Darwin
(1872/1965) illustrated how evolutionary thinking can contribute to a scientific un-
derstanding of human behavior. He argued that the basic forms of human emo-
tional expressions (such as laughing and crying) are inherited, as are those of other
animals, and may have evolved because the ability to communicate one’s emo-
tions or intentions to others of one’s kind improves one’s chances of survival.
Darwin’s work provided psychology with a scientific way of thinking about all the
inborn universal tendencies that constitute human nature. The innate mecha-
nisms underlying human emotions, drives, perceptual abilities, learning abilities,
and capacities for reason came about gradually because they promoted the sur-
vival and reproduction of our ancestors. One approach to understanding such char-
acteristics is to analyze their evolutionary functions—their ways of promoting
Charles Darwin Darwin’s principle of survival and reproduction.
evolution by natural selection helped If Kant had been privy to Darwin’s insight, he would have said that the innate
provide a scientific footing for psy-
furnishings of the mind, which make it possible for children to learn language, to
chology. The principle links humans to
the rest of the biological world and
learn about the physical world, to experience human drives and emotions, and,
explains the origin of brain mecha- more generally, to behave as human beings and not as blank sheets of paper, came
nisms that promote the individual’s about through the process of natural selection, which gradually built all these ca-
survival and reproduction. pacities into the brain’s machinery. Darwin, perhaps more than anyone else,
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CHAPTER 1 ■ FOU N DATIONS FOR TH E STU DY OF PSYCHOLOGY 9
helped convince the intellectual world that we humans, despite our pretensions,
are part of the natural world and can be understood through the methods of sci-
ence. In this way he helped make the world ripe for psychology.
We have now reached the end of the first section of the chapter, and, before >>> 11
moving on, I want to point out a second feature of the book that is designed to help How can the section review at the end of
you study it. At the end of each major section of each chapter is a section review each major section of each chapter be
used to guide one’s thought and review
that summarizes the section’s main ideas. The chart is organized hierarchically: before going on to the next section?
the main idea or topic of the section is at the top, the sub-ideas or subtopics are at
the next level down, and specific facts and lines of evidence pertaining to each sub-
idea or subtopic fill the lower parts. A good way to review, before going on, is to
read each item in the chart and think about it. Start at the top and think about the
main idea or purpose of the whole section. How would you explain it to another
person? Then go down each column, one by one; think about how the idea or topic
heading the column pertains to the larger idea or topic above it and how it is sup-
ported or elaborated upon by the more specific statements below it. If you are un-
clear about the meaning of any item in the chart, or can’t elaborate on that item in
a meaningful way, you may want to read the relevant part of the chapter again be-
fore moving on. Another way to review is to look back at the focus questions in the
margins and make sure you can answer each of them.
Psychology—the science of behavior and the mind—rests on prior intellectual developments.
▼ ▼ ▼
Physical Causation of Behavior The Role of Experience The Evolutionary Basis of
• Descartes’s dualism placed more emphasis on • The British empiricists claimed Mind and Behavior
the role of the body than had previous versions that all thought and knowledge • Darwin proposed that natural
of dualism. Hobbes’s materialism held that are rooted in sensory experience. selection leads to the evolution
behavior is completely a product of the body of behavioral tendencies (as
and thus physically caused. • They used the concept of associ-
ation by contiguity to explain how well as anatomical changes)
• To the degree that behavior and the mind have sensory experience could ulti- that promote survival and repro-
a physical basis, they are open to study just mately lead to complex thought. duction.
like the rest of the natural world. • Darwin’s thinking led to a focus
• In contrast to empiricism,
on the functions of behavior.
• Nineteenth-century physiological studies of nativism asserts that some
reflexes and of localization of function in the knowledge is innate and that • Natural selection also offered a
brain demonstrated the applicability of science such knowledge enables learning scientific basis for considering
to mental processes and behavior. from experience. nativist views.
The Scope of Psychology
Psychology is a vast and diverse field of research. Every question about behavior
and mental experience that is potentially answerable by scientific means is within
its scope. One way to become oriented to this grand science is to preview the vari-
ous kinds of explanatory concepts that psychologists use.
Varieties of Explanations in Psychology,
and Their Application to Sexual Jealousy
Psychologists strive to explain mental experiences and behavior. To explain is to
identify causes. What causes us to do what we do, feel what we feel, perceive what
we perceive, or believe what we believe? What causes us to eat in some conditions
and not in others; to cooperate sometimes and to cheat at other times; to feel
angry, frightened, happy, or guilty; to dream; to hate or love; to see red as different
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10 PART 1 ■ BACKGROU ND TO THE STU DY OF PSYCHOLOGY
from blue; to remember or forget; to suddenly see so-
lutions to problems that we couldn’t see before; to
learn our native language so easily when we are very
young; to become depressed or anxious? This is a
sample of the kinds of questions that psychologists
try to answer and that are addressed in this book.
The causes of mental experiences and behavior
are complex and can be analyzed at various levels.
The phrase level of analysis, as used in psychology
and other sciences, refers to the level, or type, of
causal process that is studied. More specifically, in
psychology, a person’s behavior or mental experience
can be examined at the neural level (brain as cause),
genetic level (genes as cause), evolutionary level (natu-
The Kobal Collection
ral selection as cause), learning level (the individual’s
prior experiences with the environment as cause),
cognitive level (the individuals’ knowledge or beliefs
as cause), social level (the influence of other people
as cause), cultural level (the culture in which the per-
Sexual jealousy in humans Like son develops as cause), and developmental level (age-related changes as cause). It is
any common human behavioral pre- convenient to group these eight levels of analysis into two categories. The first cat-
disposition, sexual jealousy can be egory is biological, and consists of neural, genetic, and evolutionary explanations.
studied at the neural, genetic, evolu-
The second category is experiential, and consists of learning, cognitive, social, cul-
tionary, learning, cognitive, social, cul-
tural, and developmental levels of
tural, and developmental explanations. You will find many examples of each of
analysis. Here the theme of sexual these eight levels of analysis in this book. Now, as an overview, I’ll describe each of
jealousy is played out by Rita them very briefly.
Hayworth, Tyrone Power, and Anthony Any given type of behavior or mental experience can, in principle, be analyzed
Quinn in a scene from the 1941 film at any of the eight levels. To illustrate that point, I will suggest, in the following de-
Blood and Sand. scriptions, ways by which each level of analysis can be applied to an understanding
of sexual jealousy. One reason for choosing sexual jealousy as the example is that
it has not, in fact, been studied very much at most of the levels, so I can describe
hypothetical ways of studying it without getting into too much factual detail. For
our purposes, sexual jealousy can be defined as the set of emotions and behaviors
that result when a person believes that his or her relationship with a sexual part-
ner, or a potential sexual partner, is threatened by the partner’s involvement with
12 <<< Explanations That Focus on Biological Processes
How do neural, genetic, and evolutionary
explanations differ from one another? How Neural Explanations All mental experiences and behavioral acts are products of
might each be applied toward an under- the nervous system. One logical route to explanation in psychology, therefore, is to
standing of jealousy? try to understand how the nervous system produces the specific type of experience
or behavior being studied. Researchers who specialize in this level of explanation
are referred to as behavioral neuroscientists.
Some behavioral neuroscientists study individual neurons (nerve cells) or small
groups of neurons to determine how their characteristics contribute to particular
psychological capacities, such as learning. Others map out and study larger brain
regions and pathways that are directly involved in some particular category of be-
havior or experience, such as speaking grammatically, seeing the shapes of objects,
or experiencing an emotion such as fear. Behavioral neuroscientists also study the
ways that hormones and drugs act on the brain to alter behavior and experience,
either in humans or in non-human animals.
To date, no neural studies of jealousy have been conducted with human subjects,
but at least one such study has been conducted with macaque monkeys (Rilling &
others, 2004). Researchers induced a jealous state in male monkeys by exposing
each male to the sight of a female, with which he had previously mated, being
courted by another male. During this experience, they measured the animal’s brain
activity using a technique called positron emission tomography (PET, described in
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CHAPTER 1 ■ FOU N DATIONS FOR TH E STU DY OF PSYCHOLOGY 11
Viewing the active brain In recent
years the field of behavioral neuro-
science has advanced greatly, due in
Hoa Qui / Picture Quest
part to new techniques for assessing
the amount of activity that occurs in
specific brain locations as a person
performs mental tasks. These neuro-
imaging techniques are discussed in
Chapter 5). The result was a preliminary mapping of specific brain areas that be-
come especially active during the experience of sexual jealousy in male macaques.
A next step, not yet taken, might be for neuroscientists to try to increase or de-
crease jealous behavior in monkeys by artificially activating or inactivating those
same areas of the brain. They might also examine people who have, through
strokes or other accidents, suffered damage to those brain areas to determine if
they have any deficits in the experience of jealousy. These are the kinds of tech-
niques regularly used by behavioral neuroscientists.
Genetic Explanations Genes are the units of heredity that provide the codes for
building the entire body, including the brain. Differences among individuals in the
genes they inherit can cause differences in the brain and, therefore, differences in
mental experiences and behavior. Researchers who attempt to explain psychologi-
cal differences among individuals in terms of differences in their genes are called
Some behavioral geneticists study non-human animals. They may, for example,
deliberately modify animals’ genes to observe the effects on behavior. Others study
people. To estimate the extent to which variation among people in some particular
trait is the result of variation in genes, researchers might assess the degree to
which genetic relatedness between people correlates with their degree of similar-
ity in that trait. A finding that close genetic relatives are more similar in the trait
than are more distant relatives would suggest that genes contribute to variation in
the trait. Behavioral geneticists might also try to identify specific genes that con-
tribute to a particular trait by analyzing the DNA (genetic material) of people who
differ in that trait.
People differ in the degree to which they are prone to sexual jealousy. Some are
easily made jealous; others are not. To measure the degree to which such differ-
ences are the result of genetic differences, researchers might assess sexual jeal-
ousy in twins. If identical twins, who share all their genes with each other, are
much more similar in jealousy than are same-sex non-identical twins, who are no
more closely related than other siblings, that would indicate that much of the vari-
ation among people in sexual jealousy is caused by variation in genes. A next step
might be to find out just which genes are involved in these differences and how
they act on the brain to influence jealousy. So far, no such studies have been done
of sexual jealousy, but you will read later of such studies of intelligence (in
Chapter 10), personality traits such as extraversion (in Chapter 15), and predisposi-
tions to mental disorders such as schizophrenia and depression (in Chapter 16).
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CHAPTER 1 ■ FOU N DATIONS FOR TH E STU DY OF PSYCHOLOGY 13
Differences among individuals in jealousy derive partly from genetic
differences, but they also derive partly from differences in past experi-
ences. Jealous reactions that prove to be effective in obtaining rewards—
such as those that succeed in repelling competitors or attracting renewed
affection from the beloved—may increase in frequency with experience,
and ineffective reactions may decrease. People and animals may also
Walter Dawn / Photo Researchers, Inc.
learn, through experience, what sorts of cues are potential signs of infi-
delity in their mates, and those cues may come to trigger jealous reac-
tions. The intensity of sexual jealousy, the specific manner in which it is
expressed, and the environmental cues that trigger it can all be influ-
enced, in many ways, by learning. Learning psychologists might study all
of those effects.
Cognitive Explanations The term cognition refers to information in the
mind—that is, to information that is somehow stored and activated by the
workings of the brain. Such information includes thoughts, beliefs, and
all forms of memories. Some information is innate to the human mind, as nativist Rat learning to press a lever To
philosophers pointed out, and other information is acquired through learning, as identify basic principles of learning,
empiricist philosophers pointed out. Some information is conscious, in the sense some learning psychologists study
the processes by which animals learn
that the person is aware of it and can describe it, and other information is uncon-
simple responses for rewards. This
scious but can still influence one’s conscious experiences and behavior. One way to thirsty rat receives a drop of water to
explain any behavioral action or mental experience is to relate it to the cognitions drink each time it presses the lever.
(items of mental information) that underlie that action or experience. Researchers
who specialize in this level of analysis are called cognitive psychologists.
You can think of mental information as analogous to the operating rules (soft-
ware) and data that are stored in a computer, which influence the way that the com-
puter responds to particular forms of input. Cognitive psychologists are interested
in specifying, as clearly as possible, the types of mental information that underlie
and make possible the behaviors that they study. For instance, a cognitive psychol-
ogist who is interested in reasoning might attempt to understand the rules by which
people manipulate information in their minds in order to solve particular classes of
problems (discussed in Chapter 10). A cognitive psychologist who is interested in
racial prejudice might attempt to specify the particular beliefs—including uncon-
scious as well as conscious beliefs—that promote prejudiced behavior (discussed in
Chapter 13). Cognitive psychologists are also interested in the basic processes by
which learned information is stored and organized in the mind, which means that
they are particularly interested in memory (discussed in Chapter 9).
In general, cognitive psychology differs from the psychology of learning in its
focus on the mind. Learning psychologists generally attempt to relate learning ex-
periences directly to behavioral changes and are relatively unconcerned with the
mental processes that mediate such relationships. To a learning psychologist: expe-
rience in the environment leads to change in behavior. To a cognitive psychologist: ex-
perience in the environment leads to change in knowledge or beliefs, and that change
leads to change in behavior.
A cognitive psychologist interested in jealousy would define jealousy first and
foremost as a set of beliefs—beliefs about the behavior of one’s beloved and some
third party, about the vulnerability of one’s own relationship with the beloved, and
about the appropriateness or inappropriateness of possible ways to react. One way
to study jealousy, from a cognitive perspective, is to ask people to recall episodes of
it from their own lives and to describe the thoughts that went through their minds,
the emotions they felt, and the actions they took. Such work reveals that a wide va-
riety of thoughts can enter one’s mind in the jealous state, which can lead to actions
ranging from romantic expressions of love to murderous violence (Guerrero & oth-
ers, 2005). Psychotherapists who use cognitive methods to treat cases of pathologi-
cal jealousy try to help their clients change their thought patterns, so they will no
longer misperceive every instance of attention that the beloved pays to someone
else as a threat to their relationship, and so they will focus on constructive rather
than destructive ways of reacting to actual threats (Bishay & others, 1996).