6。 Endorphins are neuromodulators that modify the activities of postsynaptic neurons
and may play an important role in emotional behaviors
DISCUSSION QUESTIONS
1。 A fundamental； yet often overlooked； assumption of this chapter is that Darwin’s Theory of Natural
Selection accurately explains how humans reached our current stage of development。 Indeed； it has
bee so well accepted that few students will stop to wonder how this chapter would be different
if it were incorrect。 But what if it was wrong？ 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 es 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 plicated in
many cases。 Cases are monly 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 plete recoveries。 On the other hand there are also tragic
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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 e 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 mon 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 prehending 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 prehension 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
mon； but there are also differences among those members—individuals—that can determine
whether the “fitness” of their offspring will enable them to pete 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 monly