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critical thinking regarding research findings.
Key Issues
The power of belief, the placebo effect, the double blind procedure, the scientific method and
psychology, and lie detection.
New Interviews
Christina Maslach takes an in-depth look at applied research.
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CHAPTER 2: RESEARCH METHODS IN PSYCHOLOGY
FILMS AND VIDEOS
Flatland (1965). Contemporary Films, 12 minutes
When a “square” from the two-dimensional world of Flatland tries to convince others of the existence of
a third dimension, he is harshly persecuted. This animated film illustrates beautifully the scientific
ideals of objectivity and openness to change.
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PSYCHOLOGY AND LIFE
CHAPTER 3
The Biological Bases of Behavior
LEARNING OBJECTIVES
On completion of this chapter, students should be able to:
1. Understand how biology contributes to the creation of unique individuals
2. Appreciate the complex interplay among the brain, mind, behavior, and environment that creates
the unique experience of being human
3. Understand the nature versus nurture and the heredity versus environment controversies
4. Explain Darwin’s Theory of Natural Selection and its relevance and importance to the field of
psychology
5. Offer examples when given the statement, “Genes do not code for destinies; they code for potential”
6. Describe the various methods for exploring the functions of the nervous system
7. Identify the structures and functions of the central nervous system, the peripheral nervous system,
and the autonomic nervous system
8. Describe the major structures of the brain, and identify their function
9. Explicate the basic functions of the glands in the endocrine system, and explain the role of
neurotransmitters
CHAPTER OUTLINE
I. Heredity and Behavior
A. End points of Causal Explanation
1. Nature versus Nurture
2. Heredity versus Environment
B. Evolution and Natural Selection
1. Natural Selection: Fundamental assumption of psychology
a) Charles Darwin published The Origin of the Species in 1859
b) Survival of the fittest: Only those organisms most adapted to the
environment survive
2. Genotypes: A specific genetic structure
3. Phenotypes: Outward appearance and repertory of behaviors
4. Genotype and the environment interact to yield a particular phenotype
C. Human Evolution
1. Human evolution favored two adaptations: Bipedalism and Encephalization
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CHAPTER3: THE BIOLOGICAL BASES OF BEHAVIOR
a) Bipedalism: the ability to walk upright
b) Encephalization: increases in brain size
2. Language: A third critical evolutionary milestone for humans
a) Language is the basis of cultural evolution–the ability of cultures to
respond adaptively, through learning, to environmental change. Works
much more quickly than genetic evolution.
D. Variation in the Human Genotype
1. Basic Genetics
a) Genes: Organized packets of DNA that contain the instructions for the
production of proteins
b) Genes are found on rod like structures known as chromosomes. Humans
contain 46 chromosomes, 23 from the mother and 23 from the father.
c) Estimates of the number of genes in the human genome range from 30,000
to 150,000
d) The X and Y sex chromosomes determine sex. One X comes from the
mother, and either an X or a Y comes from the father. XX = female. XY =
male.
2. Genes and Behavior: the interaction of psychology and genetics
a) Biology (genes) is (are) not destiny
b) Genes only determine the range of effects that the environment can have in
shaping phenotype and behavior
c) The person that you become is jointly determined by genes and the
environment, by nature and nurture
3. Sociobiology focuses on evolutionary explanations for social behavior and social
systems of humans and other animal species
II.Biology and Behavior
A. Early Explanations of Behavior
1. Rene Descartes argued that human physiology could be studied empirically, that
humans are just an animal machine, and that human action is a mechanical
response to the environment
2. Sir Charles Sherrington provided evidence for Descartes’ ideas and suggested that
the human nervous system involves both excitatory and inhibitory processes
3. Santiago Ramón y Cajal detected the physical gaps between adjacent neurons
4. Donald Hebb proposed that the brain is not merely a mass of tissue but a highly
integrated series of structures, or cell assemblies, that perform specific functions
5. Neuroscience is one of the most rapidly growing areas of research today
B. Eavesdropping on the Brain
1. Broca’s Area: The region of the brain that translates thoughts into speech
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PSYCHOLOGY AND LIFE
2. Producing brain lesions
a) Not done on humans for obvious ethical reasons
b) Helpful in treating some neurological disorders such as epilepsy
3. Electrical stimulation
a) Walter Hess found that sleep, sexual arousal, anxiety, and terror could be
turned on and off by electrically stimulating specific areas of the brain
4. Recording and imaging brain activity
a) Electroencephalogram (EEG) records large, integrated patterns of brain
electrical activity
b) Positron-Emission Tomography (PET) scans construct a dynamic portrait
of the brain by detecting how radioactive (but safe) substances are
processed in the brain during different cognitive and behavioral activities
c) Magnetic Resonance Imaging (MRI) uses pulses of energy to cause atoms
to align with a magnetic field. Special radio receivers then monitor the rate
at which atoms decay from alignment once the energy pulse is complete.
Computers analyze this information to create dynamic models of brain
activity.
C. The Nervous System
1. Comprised of two major divisions
a) The central nervous system (CNS), comprised of all the neurons in the
brain and spinal cord
b) The peripheral nervous system (PNS), comprised of all the neurons
forming the nerve fibers that connect the CNS to the body
2. The Central Nervous System (CNS)
a) Integrates and coordinates all bodily functions, processes all incoming
neural messages, and sends commands to different parts of the body
b) Relies on PNS for information from sensory receptors
3. The Peripheral Nervous System (PNS)
a) Provides the CNS with sensory information and relays commands from
the brain to the body’s organs and muscles
b) Composed of two subdivisions
(1) The Somatic Nervous System (SNS), which regulates the actions
of skeletal muscles
(2) The Autonomic Nervous System (ANS), which sustains basic life
processes, further divided into two subdivisions:
(i) The Sympathetic Division governs response to
emergencies
(ii) The Parasympathetic Division governs routine operation
of internal bodily functions
D. Brain Structures and Their Functions
1. The brain is the most important component of the CNS and is composed of three
layers: the brain stem, the limbic system, and the cerebrum
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CHAPTER3: THE BIOLOGICAL BASES OF BEHAVIOR
2. The Brain Stem
a) The Medulla, located at the top of the spinal cord, controls breathing, blood
pressure, and the heart
b) The Pons, located directly above the Medulla, provides inputs to other
structures of the brain stem and to the cerebellum
c) The Reticular Formation, located between the Medulla and Pons, arouses
the cerebral cortex to new stimulation and keeps the brain alert even
during sleep
d) The Thalamus, located above the Pons, receives input from the reticular
formation and channels incoming sensory information to the appropriate
area of the cerebral cortex
e) The Cerebellum, located attached to the brain stem at the base of the skull,
coordinates bodily movements and plays a role in some types of learning
3. The Limbic System mediates motivated behaviors, emotional states, and memory
processes and is composed of three structures:
a) The Hippocampus plays an important role in the acquisition of explicit
memories–memories that you are aware of retrieving
b) The Amygdala plays a role in emotional control and the formation of
emotional memories, especially those related to threat and danger
c) The Hypothalamus plays a role in maintaining homeostasis such as body
weight, temperature, and the endocrine system
4. The Cerebrum regulates higher emotional and cognitive functions
a) The Cerebral Cortex is the thin outer layer of the cerebrum
b) The cerebrum is also divided into two symmetrical halves, the cerebral
hemispheres
c) The two cerebral hemispheres are connected by a thick mass of nerve fibers
called the corpus callosum, which relays messages between hemispheres
d) Grooves in the cerebrum, called the Central Sulcus and the Lateral Fissure,
help divide each cerebral hemisphere into four lo
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