Serenity

* All the following abstractions are excerpted from <Psychology>, Peter O. Gray, 5th edition

Chapter 03 — Genetic and Evolutionary Foundations of Behavior. 

Section 1 — Review of Basic Genetic Mechanisms

Genes affect behavior by affecting the bodily structures involved in behavior.

- Nature of Genetic Influence

• Genes affect bodily structures, and thereby affect behavior, by influencing protein synthesis.

• Genes act in concert with the environment, not in isolation. For example, environmental cues can activate genes that make rats or mice nurturant to newborns.

- Meiosis and Sexual Reproduction 减数分裂和有性繁殖

• Meiosis results in egg and sperm cells that contain just one member of each pair of genes.

• Meiosis involves random assortment of paired genes.

• Genetic diversity produced by sexual reproduction promotes the genes' survival.

- Gene Pairing

• Paired genes, which occupy the same locus (location) on a pair of chromosomes, may be identical (homozygous) 纯合的 or different (heterozygous)杂合的. Gene variations that can occupy the same locus are called alleles. 等位基因

• Mendel's discovery of consistent ratios of traits in offspring of cross-pollinated strains of peas led to the gene concept and to the concepts of dominance and recessiveness. 显性/隐性基因

Section 2 — Inheritance of Behavioral Traits

Hereditary effects on behavioral traits can involve just one gene, but usually involve many.

- Single-Gene Traits  单基因性状

• Single-gene traits (controlled by one pair of genes) are categorical (all or none) in nature.

• Mendelian patterns of inheritance indicate single-gene control. 曼德尔遗传模式

• Examples are breed differences in fearfulness in dogs and a language disorder in the KE family. General lessons concerning inheritance are illustrated with each example.

- Polygenic Traits  多因特征

• Polygenic traits (influences by many gene pairs) are continuous (present in varying degrees) and often fit a normal distribution.

• Through selective breeding, a trait can be strengthened or weakened gradually over generations. 

• An example is Tryon's breeding of rats for maze ability, which illustrates certain general lessons.

Section 3 — Evolution by Natural Selection

Natural selection is the mechanism that produces evolutionary change.

- How Natural Selection Works

• To the degree that a trait enhances survival and reproduction, genes producing that trait are passed on to offspring. The result is that such genes become more frequent over generations.

• Mutations and reshuffling of genes in sexual reproduction provide genetic diversity on which natural selection operates.

- Role of Environmental Change

• The rate and nature of environmental change affect the rate and course of evolution. An example is the effect of drought on the evolution of beak thickness in finches.

• Complex changes, requiring many mutations, require a long time to evolve.

- Evolution Lacks Foresight

• Natural selection can only lead to changes that are immediately adaptive; it cannot anticipate future needs.

• There is not preset pathway for evolution.

• Natural selection is not a moral force.

Section 4 — Natural Selection as a Foundation for Functionalism

The concept of natural selection provides a secure footing for functionalism.

- The Functionalist Approach

• Functionalism is an approach to psychology that focuses on the usefulness of a particular behavior to the individual engaging in it.

• Ultimate explanations are functional explanations, stating the role that specific behaviors play in survival and reproduction.

• Proximate explanations are complementary to ultimate explanations; they are concerned with mechanisms that bring about behavior.

- Limitations of Functionalism

• Some traits are vestigial; they once served a function but no longer do.

• Some traits are side effects of other traits that arose through natural selection.

• Some traits that require few mutations are products just of change, not natural selection.

• Even evolved mechanisms, such as that for guilt, are not useful in every situation in which they are active.

Section 5 — Natural Selection as a Foundation for Understanding Species-Typical Behaviors

Species-typical behaviors have come to exist through natural selection.

- Species-Typical Behaviors  种属行为

• Commonly called instincts, species-typical behaviors are ways of behaving that characterize a species — such as cats meowing and humans walking upright.

• They may be influenced by learning or even require learning, as exemplified by cultural differences in the eyebrow flash, human language learning, and white-crowned sparrows' song development.

• They depend upon biological preparedness — i.e., upon having anatomical structures that permit and motivate the behavior.

- Homologies and Analogies

• Homologies are similarities due to common ancestry. They are useful for studying underlying mechanisms and for tracing the evolutionary course of species-typical behaviors, exemplified by research on the greeting smile and happy smile in humans.

• Analogies are similarities due to convergent evolution (independent evolution of similar traits). They are useful for inferring ultimate functions.

Section 6 — Evolutionary Analysis of Mating Patterns.

An evolutionary perspective offers functionalist explanations of mating patterns.

- Mating Patterns Related to Parental Investment

• Trivers theorized that sex differences in parental investment (time, energy, risk involved in bearing and raising young) explain mating patterns and sex differences in size, aggressiveness, competition for mates, and selectivity in choosing mates.

• Consistent with Trivers's theory, polygyny (一夫多妻) is associated with high female and low male parental investment; polyandry (一妻多夫) is associated with the opposite; and monogamy (一夫一妻) is associated with approximately equal investment by the two sexes.

• Polygynandry (多夫多妻?), common to chimps and bonobos, seems to be associated with high investment in the group.

- Human Mating Patterns

• Parental investment is somewhat lower for fathers than for mothers, consistent with the human mix of monogamy and polygyny.

• Romantic love and jealousy help promote and preserve bonding of mates, permitting two-parent care of offspring.

• Sex outside of mating bonds may yield evolutionary benefits.

Section 7 — Evolutionary Analyses of Hurting and Helping

An evolutionary perspective offers functionalist explanations of aggression and helping.

- Male Violence

• Male primates, including men, are generally more violent than are females of their species.

• Most aggression and violence in male primates relate directly or indirectly to sex. Genes that promote violence are passed to offspring to the degree that they increase mating.

• Among bonobos, female alliances counter male violence.

- Helping

• Helping (promoting another's survival or reproduction) takes two forms — cooperation and altruism.

• Cooperation (helping others while also helping oneself, as in the case of wolves hunting together) is easy to understand evolutionarily.

• Apparent acts of altruism (helping others at a net cost to oneself) make evolutionary sense if explained by the kin selection or reciprocity theories.

- Common Fallacies

• The naturalistic fallacy is the equation of what is natural with what is right. It was indulged in by Social Darwinists.

• The deterministic fallacy is the belief that genes control behavior in ways that cannot be altered by environmental experiences or conscious decisions.