Chapter 1The Major Issues

Biological Psychology

• The study of the physical roots of behavior.• Emphasizes:

– Physiology– Evolution (genetics)– Development– Brain functioning

• Brain functioning on a microscopic level: neurons and glia, the cells of the brain

Biological explanations of behavior fall into four categories:

– Physiological- emphasis on brain and other vital organs.

– Ontogenetic- describes the development of a structure or behavior.

– Evolutionary- focuses upon the genetic history of a behavior.

– Functional- describes why a structure or behavior evolved as it did.

The Mind-Brain Relationship

• Biological explanations of behavior bring into focus the relationship between the mind and the brain, also known as the “mind-body” or “mind-brain problem”.

• The “mind-brain problem” has a variety of explanations.

• Dualism is the belief that there are different kinds of substances and the mind and the body are separate entities.– Defended by French

philosopher Rene Descartes.

– Most common belief among nonscientists.

– Rejected by most neuroscientists.

The Mind-Brain Relationship

• Monism is the belief that the universe is only comprised of one type of substance.

• Forms of monism include:– Materialism- everything that exists is

physical by nature.– Mentalism- only the mind truly exists.– Identity position- mental processes are the

same as brain processes but simply described in different ways.

The Genetics of Behavior

• Both genes and environment interact to shape human behavior.

• How much of a role does genetics play in shaping human behavior?– Examples: psychological disorders, weight

gain, personality, sexual orientation, sexual identity?

“Bringing Up Monkey”

Link to Video

Heredity

• The mechanism used to pass the message of inheritance from one generation to the next.

• A trait that depends largely on hereditary influences is said to have high heritability.

Research: Twins and Adopted Children

• Researchers study monozygotic (identical) and dizygotic (fraternal) twins to infer how much of a genetic component exists for a particular behavior.

• Researchers also study adopted children and their resemblance to their biological parents to infer the influence of heredity.

Multiplier effect

Genetic tendencies that guide behavior will result in a change in the environment that magnifies the original tendency.

Traits with a strong hereditary influence can be modified by environmental intervention.

– PKU (phenylkentonuria): a genetic inability to metabolize phenylalanine that results in brain damage—unless phenylalanine is removed from the diet

Genetics of Human Life

• Chromosomes contain genetic information

• 46 chromosomes in every cell

• Exception: Sex cells (eggs and sperm) have 23

• Sexual reproduction involves making 23 new chromosome pairs

• The 23rd chromosome pair (sex chromosomes) determines sex of child

• During reproduction:

– Females contribute an X chromosome.

– Males contribute either an X or a Y chromosome that determines the sex of the child.• If X, female• If Y, male

Genes

• Basic units of heredity that maintain their structural identity from one generation to another

• Inheritance through genes was demonstrated by 19th century monk Gregor Mendel

• Strands of genes form chromosomes

Deoxyribonucleic Acid (DNA)

• A double-stranded chemical that contains genetic information

• Genes/chromosomes are composed of DNA

One strand of DNA serves as a model for the synthesis of ribonucleic acid (RNA).

Fig. 1-7, p. 12

Ribonucleic acid (RNA)

• A single strand chemical that can serve as a template/model for the synthesis of proteins.

• Proteins determine the development of the body by:• forming part of the structure of the body.• serving as enzymes that serve as

biological catalysts and regulate chemical reactions in the body.

Genes come in pairs• Homozygous for a gene:

identical pair of genes on the two chromosomes

• Heterozygous for a gene: unmatched pair of genes on the two chromosomes

• A dominant gene shows a strong effect in either the homozygous or heterozygous condition.

• A recessive gene shows its effect only in the homozygous condition.

• Pea plant flowers (parents are heterozygous for color):

Genes can be dominant or recessive

• Dominant traits:

• Recessive traits:

• Example: The ability to taste PTC (phenylthio-carbamide), a bitter organic compound, is dominant

Fig. 1-8, p. 13

Types of genes include:

• Autosomal genes - all genes except for sex- linked genes.

• Sex-linked genes - genes located on the sex chromosomes.

Human Sex-linked genes

• Y chromosome: genes for 27 proteins

• X chromosome: genes for approximately 1500 proteins

• Thus, sex-linked genes usually refer to X-linked genes. (Example: Red-green color deficiency)

• Sex-limited genes are genes that are present in both sexes but mainly have an effect on one sex (Chest hair, breast size, etc.)

Genetic Variation

• Recombination refers to a new combination of genes in the off-spring that yield characteristics not found in either parent.

• Mutation refers to a change in a single gene that is rare, random and often independent of the needs of the organism.

• Evolution refers to a change in the frequency of various genes in a population over generations

• Evolution attempts to answer two questions:

1. How did some species evolve?

2. How do species evolve?

Evolution of Behavior

• Evolutionary psychology focuses on functional explanations of how behaviors evolved.

• Assumes that behaviors characteristic of a species have arisen through natural selection and provide a survival advantage.– Examples: differences in peripheral/color

vision, sleep mechanisms in the brain, eating habits, temperature regulation.

Artificial Selection

• Organisms with desired traits are chosen to be parents of the next generation

• Used by breeders• Sometimes used by

human parents

The Use of Animals in Research

• Important source of information• Highly controversial topic• Amount of stress and/or pain that is caused to

the animal varies• Colleges and research institutions in the US

are required to have an Institutional Animal Care and Use Committee (IACUC).– Oversees and determines acceptable

procedures.

Reasons for studying animals include:

1. The underlying mechanisms of behavior are similar across species and often easier to study in nonhuman species.

2. We are interested in animals for their own sake.

3. What we learn about animals sheds light on human evolution.

4. Some experiments cannot use humans because of legal or ethical reasons.

Fig. 1-12, p. 23

The Use of Animals in Research

• Opposition to animal research varies:

– “Minimalists” favor firm regulation on research and place consideration upon the type of animal used and the amount of stress induced.

– “Abolitionists” maintain that all animals have the same rights as humans and any use of animals is unethical.