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Chapter 3

Chapter 3: Genes, Evolution, & The Environment

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PSYC 1020H
Wolfgang Lehmann

Genes, Evolution, & Environment  Evolutionary psychology: emphasizes evolutionary mechanisms that may help explain human commonalities in cognition, development, emotion, social practices, and other behavioural areas  Behavioural genetics: concerned with the genetic bases of individual differences in behaviour and personality  Nativists emphasize genes and inborn characteristics (nature), whereas empiricists focused on the learning and experience (nurture) Unlocking the Secrets of Genes  Genes are the basic units of heredity and are located on chromosomes: rod-shaped structures that carry the genes and are found in the nucleus (center) of every cell of the body  Sperm and egg cells (ovum) contain 23 chromosomes, which means that when they unite the fertilized egg and body cells contain 46 chromosomes arranged in 23 pair  Chromosomes consist of DNA molecules and genes consist of small segments of this DNA  DNA (deoxyribonucleic acid): the chromosomal molecule that transfers genetic characteristics by way of coded instructions for the structure of proteins  There are approximately 25,000 genes altogether and referred to as the ‘human’ genome: the full set of genes in each cell of an organism (except for sperm and egg cells)  Four basic elements of DNA are arranged in a particular order within each gene: adenine, thymine, cytosine, and guanine (ex. ACGTCTCTATA)  A catalogue has been developed to describe millions of patterns of human genetic variations to allow researchers to study consequences of such variations  A method of searching for genes associated with physical and mental conditions are linkage studies: they take advantage of the tendency of genes lying close together on a chromosome to be inherited together across generations; researchers begin by looking for genetic markers  Genetic markers: a DNA segment that varies among individuals, has a known location on a chromosome, and is also able to function as a genetic landmark for a gene  Linkage method was able to locate the gene responsible for Huntington’s Disease  Most human traits and human conditions are a result of more than one pair of genes: be cautious of reports indicating a ‘gene for this’ or ‘gene for that’ or anything indicating one gene is the only one to blame 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  Gene frequencies in a population change partially because during the division of cells that produce sperm and eggs, if an error occurs in the copying of the DNA sequence genes can randomly change or undergo mutation  Charles Darwin developed the theory of natural selection which said that the fate of these genetic variations depends on the environment , but he was unaware of the genes at that time  Fundamental idea of natural selection: if, in a particular environment, individuals with a genetically influenced trait tend to be more successful than other individuals in finding food, surviving the elements, and fending off enemies, and otherwise staying alive long enough to produce offspring, their genes will become better and more common in the population  That ‘survival of the fittest’ theory did not always explain all the physical and behavioural traits reflecting a gene’s success, which resulted in Darwin created a second theory called sexual selection  Sexual selection: the members of either the other sex or the same sex, with which one is competing, determines a gene’s fate; there are 2 types of sexual selection 1. Intersexual selection: a member of one sex chooses a mate from the other sex on the basis of certain characteristics (ex. Males typically choose physical factors, females choose physical factors as well as access to resources) 2. Intrasexual selection: members of the same sex compete for a partner of the other sex; males might compete with each other by becoming more muscular or displaying resources, while females enhance their appearance and try to look more youthful  Evolutionary psychologists start by asking what sort of challenges humans might have faced in their prehistoric past and then draw inferences about behavioural tendencies that may have been selected, resulting in research being done to see if those tendencies actually exist throughout the world  They say the human mind is developed as a collection as a collection of specialized and independent mental modules to handle specific survival problems (ex. Need to locate food, find a mate) Innate Human Characteristics  Many abilities, tendencies and characteristics are often present at birth due to the way our species evolved; often include some less obvious ones also: 1. Infant reflexes: babies are born with a number of reflexes (simple, automatic responses to specific stimuli) 2. An interest in novelty: babies will express interest in looking at and listening to unfamiliar things and will even stop nursing momentarily to see someone new; novelty is intriguing to all human beings 3. Desire to explore and manipulate objects: all humans have the natural impulse to handle interesting objects and can sometimes be overwhelming; babies like to shake rattles, bang pots, and grasp anything they can put into their hands 4. An impulse to play and fool around: play and exploration may be biologically adaptive because they help members of a species find food and other necessities of life and to help cope with their environment 5. Basic cognitive skills: it is believed that people are born with abilities that make it easy to learn to interpret the expressing and gestures of others, identify faces, and determine what others are thinking and feeling; infants will quickly develop the ability to understand number and differences in quantities Language  Language: a system that combines meaningless elements such as sounds or gestures to form structured utterances that convey meaning  Some nonhuman animals can acquire aspects of language through help from humans, but we are the ONLY species that seems to acquire language naturally  Language of any kind allows humans to express and comprehend an infinite number of novel utterances created on the spot, which means our language will be ever growing  Noam Chomsky argued the original belief that children acquired language through imitating adults and learning from when they corrected their mistakes, by saying that language was far too complex to learn bit by bit  Chomsky said that children figure out which sounds or gestures form words and also take the surface structure of a sentence (the way the sentence is actually spoken or signed) to infer an underlying deep structure (how the sentence is to be understood) 1. Ex. ‘Mary kissed John’ and ‘John was kissed by Mary’ obviously has the same meaning in that Mary is the kisser and John gets the kiss  A single surface structure can have two different underlying structures and one’s ability to identify two different deep structures tells you that the sentence’s meaning is ambiguous 1. Ex. ‘Bill heard the trampling of the hikers’ can be interpreted as meaning ‘Bill heard the hikers trampling (something)’ or ‘Bill heard (someone) trampling the hikers.’  Transforming structure surfaces into deep ones, the rules of grammar (syntax) must be applied as they govern word order and other linguistic features that determine the role a word plays in the sentence  Human brain must acquire a language acquisition device since no one teachers us grammar at a young age  Language acquisition device: according to many psycholinguists, an innate mental module that allows young children to develop language if they are exposed to an adequate sampling of conversation  Linguists and psycholinguists (researchers studying the psychology of language) have gathered evidence and support for Chomsky’s theory: 1. Children in different cultures go through similar stages of linguistic development  Ex. They will often form their first negatives by adding ‘no’ or ‘not’ to the beginning or end of a sentence 2. Children combine words in ways that adults never would  They use overregularizations – which are non-random grammar errors indicating that the child has grasped the grammatical rule and is generalizing it  Ex. “Let’s go to the store” is “Go store” or “Daddy taked me” 3. Adults do not consistently correct their children’s syntax, yet they learn to speak or sign correctly  It is assumed that parents reward children for speaking correctly, but actually parents reward children for incorrect sentences so long as they are understandable 4. Children not exposed to adult language might invent a language of their own  Deaf children who have never learned any standard language have actually made up their own sign languages out of thin air  Ex. Three deaf children in Nicaragua have invent
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