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Chapter 3

Chapter 3- Genes, Evolution and the Environment

7 Pages

Course Code
PSYC 1020H
Wolfgang Lehmann

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Chapter 3- Genes, Evolution and the Environment Unlocking the Secrets of Genes Evolutionary psychology- a field of psychology emphasizing evolutionary mechanisms that may help explain human commonalities in cognition, development, emotion, social practices, and other areas of behaviour Behavioural genetics- an interdisciplinary field of study concerned with the genetic bases of individual differences in behaviour and personality Genes- the functional units of heredity; composed of DNA and specify the structure of proteins  We have about 25,000 genes Chromosomes- within every cell, rod-shaped structures that carry the genes  Humans have 23 pairs- 46 chromosomes DNA (deoxyribonucleic acid) - the chromosomal molecule that transfers genetic characteristics by way of coded instructions for the structure of proteins  Composed of bases A,T,C,G – adenine, thymine, cytosine, guanine Genome- the full set of genes in each cell of an organism (except for sperm and egg cells)  Human Genome Project in 2000- about 3 billion units of DNA- combinations of A,T,C,G Nativists (nature) – emphasize genes and inborn characteristics  Edward Thorndike- “in the actual race of life… the chief determining factor is heredity” Empiricists (nurture) – focus on learning and experience  John B. Watson- blank slate of human nature: “Give me a dozen healthy infants, well- formed, and my own specified world to bring them up in…” Linkage studies- take advantage of genes lying close together on a chromosome to be inherited together across generations  Genetic marker- a segment of DNA that varies among individuals, has a known location on a chromosome, and can function as a genetic landmark for a gene involved in a physical or mental condition Genetics of Similarity Evolution and Natural Selection Evolution- a change in gene frequencies within a population over many generations; a mechanism by which genetically influenced characteristics of a population may change Mutation- changes in genes, sometimes due to an error in the copying of the original DNA sequence during the division of the cells that produce sperm and eggs  Also, during the formation of a sperm or egg, small segments of genetic material cross over (exchange places) from one member of a chromosome pair to another, before the final cell division Natural Selection  Natural selection- The evolutionary process in which individuals with genetically influenced traits that are adaptive in a particular environment tend to survive and to reproduce in greater numbers than do other individuals; as a result, their traits become more common in the population  Sexual selection- members of other sex or same sex, that they compete with, determine a gene’s fate  Intersexual selection- one sex chooses a member of the other sex based on certain characteristics  Intrasexual selection- members of same sex compete for a partner of the other sex Traits and Preferences Evolutionary psychologists: 1. Ask what challenges humans may have faced in prehistoric past 2. Infer behavioural tendencies selected because they helped forebears 3. Research to see if these tendencies actually exist throughout the world  DON’T consider whether behaviour is adaptive or intelligent in the present environment Mental Modules  A collection of specialized and independent sections of the brain, developed to handle specific survival problems, such as the need to locate food or find a mate  If a mental module module for some behaviour exists, neuroscientists should eventually discover the brain circuits or subsystems associated with it Innate Human Characteristics 1. Infant reflexes- babies born with automatic responses to specific stimuli 2. Interest in novelty- prefer unfamiliar things to things we already know 3. Desire to explore and manipulate objects- the rule “don’t touch” is often ignored 4. Impulse to play and fool around- play and exploration are important 5. Basic cognitive skills- infants can tell “more than” vs. “less than” Our Human Heritage: Language Nature of Language  Darwin wrote that language is an instinctive ability unique to humans  Language- a system that combines meaningless elements such as sounds or gestures to form structured utterances that convey meaning Innate Capacity for Language  Psychologists once assumed children acquire language by imitating adults and paying attention when adults correct their mistakes Noam Chomsky- linguist who argued that language is too complex to be learned bit by bit Surface structure- the way a sentence is actually spoken/signed Deep structure- how the sentence is to be understood Language acquisition device- according to many psycholinguistics, an innate mental module that allows young children to develop language if they are exposed to an adequate sampling of conversation Universal grammar- children are born with brains sensitive to the core features common to all languages, ex. Nouns, verbs, subjects, objects Evidence for Noam Chomsky’s Position 1. Children in different cultures go through similar stages of linguistic development  Ex. Begin to form negatives by adding “no” before the word 2. Children combine words in ways that adults never would  Errors like “taked” and “goed”  Overregularizations- non-random errors in grammar that show that the child has grasped a grammatical rule 3. Adults do not consistently correct their children’s syntax, yet children learn to speak or sign correctly anyway 4. Children not exposed to adult language might invent a language of their own  Deaf Nicaraguan children made up their own sign language 5. Infants of seven months can derive simple linguistic rules from a string of sounds Learning and Language  Some theorists argue that instead of inferring grammatical rules, children learn the probability that any given word or syllable will follow another  Computer neural networks- mathematical model of the brain that can “learn”
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