PSYC 1100 Section 2.1 Genetics & Environment

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PSYC 1100 Section 2.1 Genetics & Environment
2013-10-26 15:16:31

Sec 2.1
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  1. Nature vs. Nurture
    philosophical debate about the relative importance of inborn characteristics vs. experience
  2. Nativists
    • - Kant
    • - believed that innate or inborn mechanisms were the basis of knowledge and other important charateristics
  3. Empiricists and Associationists
    • Locke and Hume
    • believed that sensory experience was the basis of knowledge and other important characteristics 
    • - 'tabula rasa' i.e. 'blank state'
    • - learn by association, e.g. Law of temporal contiguity
  4. Modern Day version of Nature vs. Nurture Argument: Genetics vs. Environment
    False dichotomy: because for most psychological characteristics both genetic and environmental factor contribute
  5. Currently there is considerable interest in studying genetic factors
    • Genetic code: information for protein synthesis (amino acid sequence) contained in the sequence of nitrogen-containing bases in the structure of DNA
    • DNA=>mRNA=>tRNA=>proteins
    • Genotype vs. Phenotype:
    • - genotype: genetic makeup of organisms, encoded in DNA
    • phenotype: the expressed traits of an organism, is a product of genetic/environment interaction during every stage of development
    • -Behavioral characteristics are PHENOTYPES, not genotypes
    • -The genotypes associated with various behavioral phenotypes can either be located on a single gene locus or multiple gen loci (i.e. poly genetic)
    • -The vast majority of behavioral traits appear to be influenced by polygenetic coding
    • Twin Studies: look at
    • concordance (degree of agreement in characteristics between twins)
    • correlation (degree and direction of linear relation between variables)
  6. Concordance studies with Schizophrenics
    • Concordance - if one twin is schizophrenic, what is the probability that the other one is schizophrenic?
    • Degree of identical twins reared apart:
    • 15-40% depending upon the study
    • Frequency of schizophrenia in general population: 1%
    • There is a genetic predisposition towards schizophrenia
  7. Correlation studies
    • Correlation can be expressed by coefficient r
    • r values can vary between -1.0 and +1.0
    • Correlation coefficients capture how closely the relation between two variables follows a straight line
    • -  the sign of the correlation (+ or -) is related to the slope of the line
    • - the absolute value is related to how closely the data resemble a line
    • -  if the r value is nearer to 0, it means no relation, while absolute value is nearer to 1.0 reflect a stronger linear relation 
    • - an r value of -1.0 or +1.0 reflect a perfect relation between the variables
  8. Correlations Studies of IQ
    • Most correlational studies with identical twins raised apart show IQ correlation about r=0.7
    • The correlation squared (r^2) is equal to the proportion of variability in one set of IQs accounted for by variability in the other sets of IQs.
    • r^2=0.7^2=0.49
    • There is about 50% of the variability in IQ is accounted for by genetic factors