第32章
What other possible explanations could be put
forward to explain how we are and how we got this way? Such questions lie at the heart of
religion, psychology, and what it means to be human. Just over 100 years ago, Lamark’s theory of
acquired characteristics was relatively well accepted. Five hundred years ago asking such
questions was blasphemous. How may we look at human evolution, creation, or development
differently 100 years in the future?
2. A second important question relating to natural selection is whether humans continue to evolve.
Fewer and fewer genes are being removed from the gene pool as environmental threats are
identified and eliminated. Because fewer individuals succumb to environmental threats, most
humans are able to survive to reproductive maturity and perpetuate their genes. What does this
successful elimination of environmental threats portend for the long-term survivability of our
species?
3. A third related question is what comes after natural selection after environmental threats are
eliminated and everyone reproduces? What forces will shape the development of humans in the
absence of environmental threats? Social Darwinism? Cultural evolution? Technological forces?
Eugenics?
4. To what extent can individuals be held accountable for their biology? Should an individual with a
tumor that causes extraordinarily high levels of testosterone to be released receive the same
sentence for a violent crime as someone without such a tumor? What if the tumor caused a mental
disorder such as schizophrenia? Could the insanity defense be used?
5. Parents want what is best for their children. They often go to such lengths as choosing homes near
good schools and sending their children to all sorts of musical, athletic, and academic lessons.
What if the need for all of these expensive lessons would be eliminated if the parents chose their
children’s genes wisely before the children were born? What if your parents had selected your
genes so that you were better looking, smarter, more athletic, or more artistically inclined? Would
such decisions be ethical? Would you want to make them for your children? Would you have
wanted your parents to make them for you? Why or why not?
6. With the advent of modern brain imaging and scanning technologies, the way in which “death” is
often determined has also changed. Where as years ago death was determined by the cessation of
breathing and the lack of a pulse, now it is additionally determined by the lack of brain activity.
This has made the determination of when someone has actually died much more complicated in
many cases. Cases are commonly reported of people who have drowned or have been frozen, who
have not breathed for dozens of minutes and who have had no heartbeat when found, who were
revived, and sometimes have made complete recoveries. On the other hand there are also tragic
41
PSYCHOLOGY AND LIFE
cases of people who have been injured in accidents who are breathing and have a pulse, but are
labeled “brain dead.” You might discuss what “brain death” means and explore both the medical
and moral issues related to these situations.
7. Have students pick at least one task that they would normally do with their dominant hand, and
have them do it with the other hand. Writing a short in-class assignment can be fun. But you can
brainstorm and see what ideas they come up with. Ask students to discuss what problems they
encountered while trying to do things with the opposite hand.
SUPPLEMENTAL LECTURE MATERIAL
Protecting the Brain
Although the bony skull usually does a good protective job, many brains are still injured in auto and
motorcycle accidents, sports, and even at the hands of parents. Failure to wear seat belts, motorcycle or
bicycle helmets, or the right protective sports equipment can result in permanent damage to some of the
brain’s functioning.
“Many slow-learning and clumsy children with IQs in the 90s,” says pediatrician John Caffey, might have
been intelligent and normally mobile children with IQs of 120, had they not been habitually shaken and
whiplashed during infancy.” Overenthusiastic bouncing of a baby before its neck muscles are strong
enough to support the head may result in broken vessels that deprive the brain of blood and thus retard the
growth of parts of the brain. Angry slaps on the head and neck can have similar negative consequences,
even for older children.
Drugs that alter brain functions can have permanent effects if taken in excess. Some drugs, like the
chemicals in glue, when inhaled can lead to death or a lifetime of mental retardation. Brains, especially
young ones, need lots of oxygen and good nutrition. They are adversely affected by pollutants in the
environment, especially when children chew on flakes of paint that contain lead.
Although children sustain head trauma in various ways, the most common source is from blows to the head
by an adult, followed by falls from bicycles. Sadly, in a fall from a bicycle or motorcycle, the area of the brain
most likely to be traumatized is the frontal lobe, the area of the brain responsible for planning, organization,
and decision-making.
Aphasias: Frontal and Temporal Lobe Injuries
An aphasia, by definition, is difficulty in producing or comprehending speech when that difficulty is not
produced by deafness or a simple motor deficit, but caused by brain damage. Paul Broca first identified this
deficit in his observations of patients who had been injured in the area of the brain known today as the left
frontal lobe. Although Broca was unable to conduct ablations on his patients, at the autopsies following
their deaths, he repeatedly found an injury to the same area of the brain in those patients who had
manifested difficulty in the production of speech. His work was eventually connected to that of Karl
Wernicke, who found a similar area in the left temporal lobe and observed that trauma to this area resulted
in poor comprehension of speech. Taken together, we now refer to the areas pinpointed by Broca and
Wernicke as the “language center” of the brain. Individually, we refer to these areas as Broca’s area and
Wernicke’s area.
Neuroglial Cells: The Glue of Life
The term glia is derived from the Greek word for glue and is an appropriate name for the cells that surround
42
CHAPTER3: THE BIOLOGICAL BASES OF BEHAVIOR
all neurons, sealing them together. Glial cells outnumber neurons ten to one, and, though tiny in size, make
up half of the bulk of the brain. Unlike neurons, glia do not possess excitable membranes and so cannot
transmit information. Glia can take up, manufacture, and release chemical transmitters, and in so doing
may help to maintain or regulate synaptic transmission. Another hypothesis is that glia can manufacture
and possibly transmit other kinds of molecules, such as proteins. The anatomy of some glial cells is striking
in this regard, for they seem to form a conduit between blood vessels and neurons, and may bring
nourishment to the neurons. It is thought that these cells may have important functions during prenatal
development and recovery from brain injury. One role of glia is known definitely: Certain kinds of glia,
called by the tongue-twisting name of oligodendroglia, form the myelin sheath that insulates axons and
speeds conduction of the nerve impulse. A counterpart called a schwann cell performs the same role for the
peripheral nerves.
The study of glia is difficult because these tiny cells are inextricably entwined with neurons. As the most
numerous type of cell in the brain, their potential importance is vast, and investigation of their function
seems likely to yield exciting results in the near future.
Charles Darwin and Natural Selection: A Taproot of Contemporary
Psychology
Charles Darwin, and his theory of natural selection, had a greater impact on the development of modern
psychology than anyone else, and continues to have a profound effect on all of the natural sciences. Natural
selection is the one assumption with which most natural scientists agree, although its exact mechanisms
may be disputed. Darwin, a naturalist, published his theory of evolution in a book entitled On the Origin of
the Species by Natural Selection in 1859, about 20 years before the birth of experimental psychology.
Darwin’s ideas have shaped contemporary psychology in the following ways:
1. Continuity between Animals and Humans. This idea was difficult for society to accept, because
humans assumed that they were the crowning glory of creation and not subject to the natural laws
as were members of the animal kingdom. Even those scientists who applauded Darwin’s theory
had some difficulty in accepting the idea that evolution applied to humankind.
2. Individual Differences. The various members of a given species may have many characteristics in
common, but there are also differences among those members—individuals—that can determine
whether the “fitness” of their offspring will enable them to compete successfully in the battle for
survival.
3. The Importance of Adaptability. Survival depends on the ability of an organism to adapt to the
environment and to changes in that environment. Failure to adapt means extinction. Ninety-nine
percent of all organisms that have even lived on earth are already extinct.
4. The Importance of the Environment. The surrounding environment changes, over time, and
“fitness” means making the various physical and behavioral changes that are appropriate for
survival.
5. Emphasis on Change. Before evolutionary theory, the commonly held view was that the earth and its
inhabitants were immutable and static. Darwin’s portrayal of nature is dynamic, mutable, and
interacting.
Darwin’s ideas influenced many psychologists, including Freud, Watson, Skinner, and James. The most
apparent legacy from Darwin to Freud’s theory was the idea of the continuity of animals and humans.
Freud thought humans were driven by the same instincts that motivate other animals—instincts to survive
43
PSYCHOLOGY AND LIFE
and reproduce. According to Freud, people have no inherently higher nature than do animals, and
whatever in humans may be higher (sympathy, altruism, unselfishness) is a product of the processes of
repression and reasoning. In Freud’s perspective, the dominant force in the structure of personality is the id
(the representation of the instincts for survival and reproduction), but humans develop other aspects of
personality to control these instincts in order to adapt to communal lifestyles. Communal living is
important in terms of adaptive behavior for humans because humans are rather weak creatures compared to
the large predators.
The idea of continuity between animals and humans also influenced the behaviorist theories of Watson and
Skinner. Watson began his career as an animal psychologist believing, as later did Skinner, that the basic
principles of behavior can be discovered by studying the behavior of animals. Though behaviorists do not
deny individual differences in genetic endowment, they do tend to place greater emphasis on
environmental determinants of behavior. Skinner emphasized learning rather than innate factors as being
the antecedent of behavior, believing that through a process of trial and error, organisms learn which
behaviors lead to reinforcement-things that ensure survival and reproduction-and which behaviors are
futile, and are followed by loss or punishment. Thus, according to behaviorists, learning is our primary tool
for adaptation, and it is the environment that shapes behavior, rather than “mind” or “consciousness”
within the organism.
Behaviorism also emphasizes change. Both Watson and Skinner suggested that a utopian society could be
built by imposing proper control on environmental conditions. Emphasis on change is one of the hallmarks
of our society; we are convinced that we can be better, thinner, smarter, richer, and happier. Psychologists
have been in the forefront in convincing us that change is possible, though not necessarily easy.
The idea of adaptation to the environment was the central Darwinian theme in the functionalism of William
James and the originators of the functionalist approach. Human behavior (James used the term “habits”)
was considered in terms of how it served the goal of adaptation. Like the behaviorists, the functionalists
saw learning as the primary mechanism for human adaptation and survival.
A precursor of functionalism was the British intellectual giant, Sir Francis Galton. Using Darwin’s theory,
Galton developed a keen interest in individual differences and strived to devise ways to measure these
differences. American psychologists eagerly adopted his ideas, with their emphasis on individualism.
Psychological testing developed from this facet of functionalism and continues to be an active area in
American psychology. We have developed psychological tests to measure almost any trait you can imagine.
Ironically, the founder of psychology as a science, Wilhelm Wundt, was not significantly influenced by
Darwin’s theory, and when Wundt’s branch of psychology, structuralism, migrated to America, it was
unable to adapt and survive.
BIOGRAPHICAL PROFILES
Rene Descartes (1596—1650)
Born of wealthy parents in La Haye, France, Descartes was one of the most influential thinkers of the
Renaissance. He contributed to mathematics, philosophy, psychology, and physiology. Descartes, a very
private man, enjoyed solitude and was iconoclastic. While enrolled at a Jesuit school, he convinced the
school authorities to allow him to sleep until 11 A.M., because he did his best thinking while in bed.
Perhaps because of this individualistic nature, Descartes began to doubt all that he had learned in school.
This skepticism soon spread to all areas of his life. Descartes doubted everything. Of one thing, however,
Descartes had no doubt: that he was doubting. This led to his famous conclusion, “Cogito, ergo sum.” “I
think, therefore I am”, which suggests that all that is certain concerning the human condition is that each of
us exists. Descartes also made significant contributions to physiology. He believed that what distinguished
living from nonliving material was “animal spirits”. Animal spirits, according to Descartes, gave humans
44
CHAPTER3: THE BIOLOGICAL BASES OF BEHAVIOR
their ability to move and worked mechanically, like hydraulics. Although his notion of animal spirits has
been shown incorrect, his study of both animals and humans paved the way for future discoveries.
Descartes also addressed the mind—body problem. He thought that there was a physical body that could be
studied scientifically and that there was a mind that was not physical and that could not be studied
scientifically. He felt that the mind and body interacted in the pineal gland, which sits at the center of the
base of the brain. His position was thus dualistic and interactionist.
Because of interference by the Catholic Church and increased demands on his time because of his growing
fame, Descartes moved to Sweden in 1650 to tutor Queen Christina. Unfortunately for humanity, Queen
Christina insisted on being tutored at 5 A.M., well before Descartes’ 11 A.M. wake-up time. Within six
months of his arrival in Sweden, Descartes contracted pneumonia and died.
Paul Broca (1824—1880)
Born in Sainte-Foy-la-Grand, France, Broca was the only son of a physician, and followed his father’s lead,
becoming professor of surgery and anthropology in Paris in 1861. During an autopsy on a patient who had
suffered from severe speech deficits, Broca discovered a lesion in the left frontal lobe. This discovery was the
first evidence supporting Franz Gall’s notion of localization of brain function, a concept that is generally
viewed as accurate by current standards.
Broca was also responsible for developing the early science of craniometry, the measurement of the skull,
and the anthropological study of the prehistoric practice of trephining, in which small holes were made in
the skull of presumably mentally ill individuals in an attempt to allow demons to escape. He was elected to
the French Senate in 1879 and his radical political views included the recommendation that public high
schools open their doors to females.
Franz Gall (1758—1828)
Gall was born in Baden, Germany, but settled in Vienna as a physician. He was a distinguished anatomist,
responsible for much of our early understanding of the nervous system, particularly the distinction between
the function of the white (myelinated) and gray (nonmyelinated) matter of the brain. Along with his student,
Johann Spurzheim, Gall promoted the science of phrenology, in which a person’s character, and emotional
and intellectual dispositions could be inferred from an assessment of the various bumps and contours of the
head. Although long since discredited as legitimate science, phrenology was extremely popular in its day.
(Darwin was nearly kept off the HMS Beagle because of the shape of his nose.) Nearly 30 phrenological
societies were in existence in England in 1832, and a number of professional periodicals concerning
phrenology flourished curing the mid-1800s.
Gregor Mendel (1822—1884)
Born in Heizendorf, Austria, Mendel’s father was a peasant, his mother a gardener. After studying
philosophy at the University of Olmutz, Mendel entered the Augustinian monastery, where many of his
teachers also taught science and philosophy at the Gymnasium or Philosophical Institute. Mendel was put
in charge of the experimental garden, where he began the studies that would come to be identified as the
founding of the science of genetics. Conducting impressively systematic and thorough experiments of
hybridization of peas, Mendel accumulated evidence contradicting the current theory that inheritance was
a “blending” or combining process.
Mendel’s research was first presented at a scientific meeting in 1865 and in published form in 1866, but
went unnoticed. In 1900, however, three separate scientists reported similar findings, despite having been
ignorant of Mendel’s work.
45
PSYCHOLOGY AND LIFE
Roger Sperry (1913—1994)
Sperry obtained his M.A. in psychology at Oberlin College, followed by a Ph.D. in zoology from the
University of Chicago in 1941. He conducted postdoctoral research under Karl Lashley at Harvard and at
the Yerkes Primate Center. His early research challenged the traditional notion that nerves from sense
organs attach to brain areas in nonspecific ways. Later, he and his students advanced the psychological
study of split-brain patients by developing laboratory tasks that allowed for precise assessment of the
frequently subtle impairments experienced by recipients of the radical operation. In 1981, he was awarded
the Nobel Prize in physiology, primarily for his pioneering work during the 1960s on split-brain
phenomena. Sperry wrote later about the mind-body relationship and the ethical implications of modern
research on brain physiology and behavior.
46
CHAPTER3: THE BIOLOGICAL BASES OF BEHAVIOR
TIMELINE
Yea Event
r
1662 Rene Descartes, a French philosopher—mathematician, published Trait de L’homme, introducing
the idea of reflexive behavior.
1687 Isaac Newton published Principia.
1739 David Hume published Treatise on Human Nature.
1831 Charles Darwin set sail on the five-year voyage of the HMS Beagle
18611865
The American Civil War was fought.
1865 Gergor Mendel reported his findings on genetic transmission of traits in garden peas.
1870 Gustav Fritsch and Eduard Hitzig used electrical stimulation to study the cerebral cortex.
1875 Walther Flemming, Strasburger, and others discovered chromosomes.
1884 Oscar Hertwig suggested that nucleic acid was the material responsible for the transmission of
hereditary traits.
19141918
World War I was fought.
1929 Karl Lashley published Brain Mechanisms and Intelligence, a monograph outlining his ideas on the
relation between the brain mechanisms and learning.
1933 Ramón y Cajal published Neuron Theory or Reticular Theory?