PSY 302 Chapter 5: ch5
Biology and Behaviour
• The study of twins-- nature vs nurture --
o Twins that are genetically identical, but grow up in diff cities and meet each other only
when they are adults
o From the minnesota study of twins reared apart -- pairs of twins were located and brought
to minneapolis to undergo a battery of physiology and psychological tests -- found that
there were lots of similarities btwn two participants ( Jack and Oskar, both born in
trinidad but Jack was raised in Germany as a catholic and nazi and Jack raised in
carribean as a jew)-- ie:
▪ Held several similar jobs and being volunteer firemen
▪ It’s easy to think that the similarities are due to genetic background however env
may have contributed too -- genes code for proteins and not something as
complex as occupation
▪ Note: there is the practice of selective placement where adoption agencies
usually try to place children with families of the same general background and so
env of sep siblings are often similar in many ways
▪ Note: majority of twins in most behaviour genetics studies are predominantly
white, middle class families in western countries -- new studies are emerging on
sep twins in other countries ie: prospective longitudinal study focused in China
born twins separated by international adoption
o Help understand individuals differences among children
Nature and nurture
• Before understanding of heredity, there was though and that certain traits run in families --
farmers practicing selective breeding to improve certain characteristics of their livestock- size of
horses, the milk yielded from cows and goat etc
• Galton- a cousin of Charles darwin studied men who achieved eminenve in variety of fields and
concluded that talent ran in the family -- while english philosophers john mill pointed out that
most of galton’s eminent men were members of well off families -- where the achievement fo the
men were not biological ties but bc they had similar economic well being, social status, education
and opportunities-- that eminence were more from env factors than hereditary ones (genetic)
• Mendel-- father of heredity -- where he cross bred pea plants that were either green or yellow
• Watson, crick ( ROSALIND FRANKLIN) -- identification of structure of DNA - the basic
component of hereditary transmission
• Due to this discovery- researchers have been able to progere and map entire genome of
organism’s gene -- including humans, chickens, mice, chimps and several extinct species, ( ie:
neaderthals) -- by 2015, over 250 animal species have had their genomes sequenced
• Genome sequencing paves the way to allow for gene synthesis
• Genome: complete set of genes of any organism
• As research better understands the role of heredity, it also able to determine and identify the
limits of what these factors scan account for
• Note that development results from the close and continual interplay of nature and nurture- of
genes and experience-
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Genetic and environemtal forces
• 3 key elements of the model of heredity
o Genotype: genetic material an individual inherits
