Chapter 1 The Major Issues The Mind-Brain Relationship • Biological Psychology is the study of the physiological and genetic basis of behavior. • Emphasis is placed upon physiological, evolutionary and developmental mechanisms of behavior. • A strong emphasis is placed upon brain functioning. Fig. 1-1, p. 2 The Mind-Brain Relationship • Brain functioning can be explained at a more microscopic level in terms of neuron and glia activity. Fig. 1-2, p. 3 The Mind-Brain Relationship • 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 evolutionary history of a behavior. – Functional- describes why a structure or behavior evolved as it did. The Mind-Brain Relationship • Deep understanding of a particular behavior is tied to being able to explain the behavior from each of these perspectives. The Genetics of Behavior • Both genes and environment interact to shape human behavior. • The fundamental issue is how much a role genetics do play in shaping human behaviors. – Examples: psychological disorders, weight gain, personality, sexual orientation? The Genetics of Behavior • Genes are basic units of heredity that maintain their structural identity from one generation to another. • Genes are aligned along chromosomes (strands of genes) and come in pairs. The Genetics of Behavior • A gene is a portion of a chromosome and is composed of deoxyribonucleic acid (DNA). • DNA serves as a model for the synthesis of ribonucleic acid (RNA). Fig. 1-7, p. 12 The Genetics of Behavior • RNA is a single strand chemical that can serve as a 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 reaction in the body. The Genetics of Behavior • Homozygous for a gene means that a person has an identical pair of genes on the two chromosomes. • Heterozygous for a gene means that a person has an unmatched pair of genes on the two chromosomes. The Genetics of Behavior • Some genes can be either dominant or recessive. – Examples: eye color, breast cancer genes, ability to taste PTC, curly hair • A dominant gene shows a strong effect in either the homozygous or heterozygous condition (DD, Dd, or dD). • A recessive gene shows its effect only in the homozygous condition (dd). Fig. 1-8, p. 13 The Genetics of Behavior • Each chromosome participates in reproduction independently of the others. • Each species has a certain number of chromosomes. • Crossing over occurs when a pair of chromosomes break apart during reproduction and reconnects and attaches to the second chromosome. – BC & bc Bc & bC The Genetics of Behavior • Types of genes include: – Autosomal genes - all genes except for sex- linked genes. – Sex-linked genes - genes located on the sex chromosomes. • In mammals, the sex chromosomes are designated X & Y. – Females have two X chromosomes (XX). – Males have an X and a Y chromosome (XY). The Genetics of Behavior • During reproduction: – Females contribute an X chromosome. – Males contribute either an X or a Y chromosome that determines the sex of the child. • If an X chromosome is contributed by the male, the off-spring is female. • If a Y chromosome is contributed by the male, the off-spring will be male. The Genetics of Behavior • The human Y chromosome has genes for 27 proteins • The human X chromosome has genes for approximately 1500 proteins. • Thus, sex-linked genes usually refer to Xlinked genes. (Example: Red-green color deficiency, Hemophilia) • Sex-limited genes are genes that are present in both sexes but mainly have an effect on one sex (Chest hair, breast size, etc.) The Genetics of Behavior • Sources of variation in a species that allows for evolution to occur include: • 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. The Genetics of Behavior • Almost all behaviors have both a genetic component and an environmental component. • Researchers study monozygotic and 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. The Genetics of Behavior • Heritability • Estimates of hereditary influences are often difficult to infer and are prone to error. • Sources of error include the following: – The inability to distinguish between the effects of genes and prenatal influences. – Environmental factors can inactivate genes. The Genetics of Behavior • Sources of error (con’t) – 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 by modified by environmental intervention. • e.g. PKU---phenylketonuria The Genetics of Behavior • Genes do not directly produce behaviors. • Genes produce proteins that increase the probability that a behavior will develop under certain circumstances. • Genes can also have an indirect affect. – Genes can alter your environment by producing behaviors or traits that alter how people in your environment react to you. The Genetics of Behavior • 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? The Genetics of Behavior • How species did evolve involves the tentative construction of “evolutionary trees”. • How species do evolve rests upon two assumptions: 1. Offspring generally resemble their parents for genetic reasons. 2. Mutations and recombination of genes introduce new heritable variations that help or harm the chance of survival and reproduction. The Genetic of Behavior • Common misconceptions about evolution include the following: – Lamarckian evolution - “The use or disuse of some structure or behavior causes an increase or decrease in that behavior.” – “Humans have stopped evolving.” – “Evolution means improvement.” – “Evolution acts to benefit the individual or the species.” The Genetics of Behavior • Evolutionary psychology (sociobiology) focuses upon 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. The Genetics of Behavior • Some behaviors are more debatable regarding the influence of natural selection. • Examples include: – Life span length – Gender differences in sexual promiscuity – Altruistic behavior The Use of Animals in Research • Animal research is an important source of information for biological psychology but remains a highly controversial topic. • Animal research varies on the amount of stress and/ or pain that is caused to the animal itself. The Use of Animals in Research • 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 • Justification for research considers the amount of benefit gained compared to the amount of distress caused to the animal. – No clear dividing line exists. • Colleges and research institutions in the United States are required to have an Institutional Animal Care and Use Committee. – Oversees and determine acceptable procedures.