AP Psychology
Topic III: Biological Bases of Behavior
Chapter Two – Neuroscience and Behavior
I. Neural Communication
A. Neurons – a nerve cell; the basic building block of the nervous system.
1. Fibers of Neurons
i. Dendrites – the busy, branching extensions of a neuron that receives messages and conduct impulses toward the cell body.
ii. Axons – the extensions of a neuron, ending in branching terminal fibers, through which messages are sent.
a. Myelin sheath – insulates the axons, help speed impulses.
2. Action Potential – a brief electrical charge that travels down the axon.
i. Charge is fired when a neuron receives a signal from sense receptors or chemical messages.
ii. This charge is real electricity – a handful of neurons can power a flashlight bulb.
3. The Chemistry-to-Electricity process involves the exchange of electrically charged atoms, called ions.
i. Interior of axon has negatively charged ions.
ii. Fluid outside axon has positively charged ions.
4. Threshold – the level of stimulation required to trigger a neural impulse.
i. The neuron must decide to act based on:
a. Excitatory signals – accelerators.
b. Inhibitory signals – brake.
ii. Increasing the stimulus above the threshold will not increase the impulse intensity.
B. How Neurons Communicate.
1. Synapse – the junction between neurons.
2. Neurotransmitters – chemical messengers that traverse the synaptic gaps, binding the sending neuron to receiving neuron, thereby influencing whether to generate a neural impulse.
C. How Neurotransmitters Influence Us.
1. Kinds of Neurotransmitters:
i. Dopamine – influence movement, learning, attention, and emotion.
ii. Serotonin – affects mood, hunger, sleep, and arousal.
iii. Norepinephrine – helps control alertness and arousal.
iv. Gamma-Amino butyric Acid (GABA) – serves inhibitory functions and is sometimes implicated in eating/sleeping disorders.
v. Acetylcholine (Ach) – works on neurons involved in muscle action, learning, and memory (i.e. muscle contraction).
2. Endorphins (“morphine within”) – natural, opiate like neurotransmitters linked to pain control and to pleasure.
3. How drugs and other chemicals alter neurotransmission.
i. Agonist – similar enough to neurotransmitter to mimic its effect.
ii. Antagonist – block neurotransmitter or diminish its release.
II. The Nervous System.
A. The Peripheral Nervous System (see color chart on pg. 55)
B. Central Nervous System (brain and spinal cord).
1. Spinal Cord and Brain.
i. The spinal cord is an information highway connecting the peripheral nervous system to the brain.
2. Neural Networks.
i. The other part of your central nervous system, your brain, receives information, interprets it, and decides responses.
ii. Neural Networks are neurons clustered into work groups. (makes for fast connections)
iii. Consider: 30 billion neurons, each with 10,000 contacts with other neurons, you end up with 300 Trillion cortical synaptic connections.
III. The Brain.
A. Tools of Discovery.
1. Lesion – tissue destruction. A brain lesion is a naturally or experimentally caused destruction of brain tissue.
2. Clinical Observations – for example, the right side of the body is wired to the brain’s left side, and vice versa.
3. Manipulating Brain – scientist can simulate various parts of the brain to study effect.
4. Recording the Brain’s Electrical Activity.
i. Electroencephalogram (EEG) – an amplified recording of the waves of electrical activity that sweep across the brain’s surface. EEG can detect the electrical pulse in a single neuron.
5. Neuroimaging Techniques.
i. CT (computed tomography) Scan (also called CAT Scan).
a. Examines brain by x-ray.
b. Gives composite representation of a slice.
ii. PET (positron emission tomography) Scan – a visual display of brain activity that detects where an injected radioactive form of glucose goes while the brain performs a given task.
iii. MRI (magnetic resonance imaging) – a technique that uses magnetic fields and radioactive waves to produce computer-generated images that distinguish among different types of soft tissue; allows us to see structures within the brain.
6. Data from different brain-imaging techniques are appearing faster than anyone can read and remember them. This is the golden age of brain science.
B. Lower-Level Brain Structures.
1. The Brainstem – the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull, the brainstem is responsible for automatic survival functions. (figure 2.13, pg. 61)
i. Medulla – the base of the brainstem, controls heartbeat and breathing.
ii. Reticular (“netlike”) Formation – a nerve network in the brainstem that plays an important role in controlling arousal.
iii. The Thalamus – the brain’s sensory switchboard, located on top of the brainstem, it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla.
2. The Cerebellum – the “little brain” attached to the rear of the brainstem; it helps coordinate voluntary movement and balance.
3. The Limbic System – a doughnut-shaped system of neural
structures at the border of the brainstem and cerebral hemispheres; associated with emotions and drives. Includes the
hippocampus, amygdala, and hypothalamus. (figure 2.15, pg. 63)
i. The Amygdala – two almond-shaped neural clusters that are components of the limbic system and are linked to emotion, in particular, aggression and fear.
ii. The Hypothalamus – a neural structure lying below (hypo) the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to emotion.
C. The Cerebral Cortex – the intricate fabric of interconnected neural cells that covers the cerebral hemispheres; the body’s ultimate control and information-processing center.
1. Structure of the Cortex (figure 2.18, pg. 65)
i. Glial cells – cells in the nervous system that are not neurons but support, nourish, and protect neurons.
ii. Each brain hemisphere is divided into four regions, or lobes.
a. Frontal Lobes – the portion of the cerebral cortex lying just behind the forehead; involved in speaking and muscle movement and in making plans and judgments.
b. Parietal Lobes – the portion of the cerebral cortex lying at the top of the head and toward the rear; includes the sensory cortex.
c. Occipital Lobes – the portion of the cerebral cortex lying at the back of the head; includes the visual areas, which receive visual information from the opposite visual field.
d. Temporal Lobes – the portion of the cerebral cortex lying roughly above the ears; includes the auditory areas, each of which receives auditory information primarily from the opposite ear.
2. Functions of the Cortex – hard to localize brain function, the brain involves integrated activity from different sections. However, scientist have localized simpler brain function.
i. Motor Function
a. Motor Cortex – an area at the rear of the frontal lobes that controls voluntary movement.
ii. Sensory Function
a. Sensory Cortex – the area at the front of the parietal lobes that registers and processes body sensation.
iii. Association functions
a. Association Areas – areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking,
b. These areas interpret, integrate, and act on information processed by the sensory areas.
c. We can’t neatly specify the functions of the association areas, but they are highly important. (There is no apparently purposeless tissue in the brain.)
iv. Language – intricate coordination of many brain areas. (see chart 2.23, pg. 70)
a. Damage to any one of several cortical areas can cause aphasia. Aphasia is impairment of language, usually caused by left hemisphere damage either to Broca’s area or Wernicke’s area.
b. Broca’s Area – an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movement involved in speech.
c. Wernicke’s Area – a brain area involved in language comprehension and expression; usually in the left temporal lobe.
3. Brain Reorganization
i. Plasticity – the brain’s capacity for modification, as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development.
D. Our Divided Brain.
1. Splitting the Brain
i. Corpus Callosum – the large band of neural fibers connecting the two brain hemispheres and carrying messages between them.
ii. Split brain – a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers between them.
2. Studying hemispheric Differences in the Intact Brain.
i. There are hemispheric specializations in the undivided brain.
a. Perceptual tasks tend to be right hemisphere.
b. Speaking and calculating tend to be left hemisphere.
IV. The Endocrine System the body’s “slow” chemical communication system; a set of glands that secret hormones into the bloodstream. (see chart 2.30, pg. 81)
A. Hormones – chemical messengers, mostly those manufactured by the endocrine glands, which are produced in one tissue and affect another.
B. Adrenal Glands – located on top of kidneys, secrete the hormones epinephrine (adrenaline) and norepinephrine (noradrenaline), which help to arouse the body in times of stress.
C. Pituitary Gland – the endocrine system’s most influential gland. Under the influence of the hypothalamus, the pituitary regulates growth and controls other endocrine glands.
D. There is an intimate connection between the nervous system and endocrine system. The connections are so close, the distinction between them sometimes blurs.
Chapter 3 – The Nature and Nurture of Behavior
I. Genes: Our Biological Blueprint.
Genome – the complete instructions for making an organism, consisting of all the genetic material in the chromosomes. The human genome has 3 billion weakly bonded pairs of nucleotides organized as coiled chains of DNA.
II. Evolutionary Psychology: Explaining Universal Behaviors.
A. Natural Selection – the principle that, among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed.
1. Mutations – random errors in gene replication that lead to a change in the sequence of nucleotides; the source of all genetic diversity.
2. Sexuality.
i. Largest gender difference is that males are more likely to initiate sexual activity and are more accepting of casual sex. Women are more relational.
ii. Gender differences in attitudes extend to differences in behavior.
3. An Evolutionary Explanation.
i. Our natural yearnings are our genes’ way of reproducing themselves.
a. How did our ancestors send their genes into the future? Women by pairing wisely, men by pairing widely.
ii. Men across cultures tend to judge women as more attractive if they have a youthful appearance. This seems to relate to the number of childbearing years.
iii. Women feel attracted to men who are healthy, mature, dominant, and affluent. (Support & Protect)
4. Critiquing the Evolutionary Explanation.
i. Critics maintain that evolutionary psychologist make too many hindsight explanations.
ii. Reinforces male-female stereotypes.
iii. Much of who we are is not hard-wired.
III. Behavior Genetics: Explaining Individual Differences.
(Behavior Genetics – the study of the relative power and limits of genetic and environmental influences on behavior.)
A. Twin Studies
1. Identical Twins – develop from a single fertilized egg, creating two genetically identical organisms.
2. Fraternal Twins – develop from two separate eggs and are no genetically closer than any other sibling, but they do share fetal environment.
3. Studies confirm that identical twins are much more similar across the board than fraternal twins.
4. Separated twins also tend to share similar personality, abilities, attitudes, interest, and even fears.
B. Adoption Studies
1. Studies the question, “Are adopted children more like their adoptive parents or biological parents?”
2. Answer – Adoptee’ personality traits bear more similarities to their biological parents than to adoptive parents.
3. Adoptive parents, while having a limited influence on personality, do influence a child’s attitudes, values, manners, faith, and politics. Parenting matters!
C. Temperament Studies
1. Temperament – a person’s characteristic emotional reactivity and intensity.
2. Temperament endures through life.
3. Genetic influence predisposes us to a certain temperament.
D. Heritability – the proportion of variation among individuals that we can attribute to genes. The heritability of a trait may vary, depending on the range of populations and environments studied.
1. We can never say what percentage of an individual’s personality or intelligence is inherited.
2. Group Differences
i. Genes do not always account for group differences.
ii. Consider how nutrition has drastically changed height and weight in a mere century.
3. Nature Enables Nurture
i. Genes and environment work together like two hands clapping.
E. Gene-Environment Interaction – from conception onward, we are a product of a cascade of interactions between genetic predispositions and our surrounding environments.
F. The New Frontier: Molecular Genetics – the sub field of biology that studies the molecular structure and function of genes.
1. Working to identify the specific genes that influence behaviors.
2. While having benefits, can also have ethical issues (i.e. designer babies, etc.)
IV. Environmental Influence
A. How Much Credit (or Blame) Do Parents Deserve.
1. Shared environmental influences typically account for less than 10 percent of personality differences among siblings, though it accounts for more of their beliefs and values.
B. Prenatal environment
1. “Nurture” begins in the womb.
2. Even with identical twins, one may have a richer blood supply and weigh more at birth.
C. Experience and Brain Development.
1. Experience helps develop the brain’s neural connections.
2. For us to have optimum brain development, normal stimulation during the early years is critical.
3. The maturing brain seems governed by a rule: Use it or lose it!
D. Peer Influence
1. Experiences with peers powerfully socialize children and youth (i.e. accents).
2. Selection Effect – kids seek out peers with similar attitudes and interests.
3. Parents and Peers are complementary.
i. Parents contribute to education, discipline, responsibility, orderliness, charitableness, and ways of inter-acting with authority figures.
ii. Peers are more important for learning cooperation, popularity, and styles of inter-action among people of the same age.
E. Culture – the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people and transmitted from one generation to the next.
1. Variations Across Cultures
i. Norms – an understood rule for accepted and expected behavior. Norms prescribe “proper” behavior.
ii. When cultures collide, their differing norms often befuddle. (i.e. personal space and punctuality)
2. Variation Over Time
i. Some cultures change rapidly over time.
ii. Memes – Self-replicating ideas, fashions, and innovations passed from person to person.
3. Culture and Child-Rearing
i. Children across place and time have thrived under various child-rearing systems.
a. We can’t assume that our culture’s way is the only way to rear children successfully.
5. Developmental Similarities Across Groups
i. Similarities are predisposed by our shared biology.
ii. Styles may differ, but universal principles prevail.
V. Gender
A. The Nature of Gender
1. Males and females are variations on a single form. The differences arise from their differing chromosomes and hormones.
i. X Chromosome – the sex chromosome found in both men and women. Females have two X chromosomes; males have one. An X chromosome from each parent produces a female.
ii. Y Chromosome – the sex chromosome found only in males. When paired with an X sex chromosome from the mother, it produces a male child.
iii. Testosterone – the most important of the male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth of the male sex organs in the fetus and the development of the male sex characteristics during puberty.
B. The Nurture of Gender
1. Gender Roles
i. Role – a set of expectations (norms) about a social position, defining how those in the position ought to behave.
ii. Gender Role – a set of expected behaviors for males and for females.
iii. Gender roles are not rigidly fixed by evolution, because they vary across cultures.
iv. Societies typically socialize their children into distinct gender roles.
v. Gender roles have changed dramatically over the past century.
2. Gender and Child-Rearing
i. Gender Identity – one’s sense of being male or female.
ii. Gender-Typing – the acquisition of a traditional masculine or feminine role.
iii. Social Learning Theory – the theory that we learn social behavior by observing and imitating and by being rewarded or punishment.
a. The difference in the way parents rear boys and girls aren’t enough to explain gender typing.
iv. Gender Schema Theory – the theory that children learn from their cultures a concept of what it means to be male and female and that they adjust their behavior accordingly.
a. Combines social learning theory with cognition. (figure 3.8, pg. 114)
VI. Postscript: Reflections on Nature and Nurture
A. Our genes and our experience together form who we are.
B. We are both creatures and creators of our worlds.
1. The stream of causation that shapes the future runs through our present choices.
2. We are a product of nature and nurture, but we are also an open system.
3. “Bad Faith” – we can’t evade responsibility by blaming bad genes or bad influences for one’s fate (Jean-Paul Sartre).