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Shared and Unshared environments

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Shared and Unshared environments The findings that MZ twins reared together (same genes, same environment) do not yield perfect concordance rates have prompted ... – PowerPoint PPT presentation

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Title: Shared and Unshared environments


1
Shared and Unshared environments
  • The findings that MZ twins reared together (same
    genes, same environment) do not yield perfect
    concordance rates have prompted psychologists to
    search for a possible explanation.
  • As a result, psychologists have begun to focus on
    the unshared environments of siblings. It does
    not follow that because 2 children are brought up
    in the same home they share the same environment.
    Individuals from the same home may have different
    experiences, friends, teachers, hobbies etc.
  • Furthermore, the same experience may have
    differing effects on each person, thus creating
    different environments. For example, a parent may
    become unemployed when one child is 13 years old
    and the other is only a toddler. The same
    experience may have a different effect on each
    child because of their age.
  • Elder (1974) found that paternal unemployment
    during the Great Depression had different effects
    on a child depending on the age and sex of the
    child.
  • Chance factors such as accidents and illnesses
    are further examples of unshared nurture.
  • TASK You need to explain the information above
    to the rest of the class, you also need to
    include in your feedback at least one example of
    something which supports the idea of unshared
    nurture despite siblings being reared together.

2
Interaction of heredity and the environment
  • Psychologists have recently become interested in
    unshared environmental influences (i.e. siblings
    who are reared together may still experience life
    very differently). These unshared influences were
    neglected until recently because they interact so
    closely with genetic factors as to not be easily
    recognised.
  • For example, an individuals innate
    characteristics may elicit particular responses
    from people. For example, a baby genetically
    predisposed to be sociable and easy-going will
    attract more affectionate and stimulating care
    than a difficult baby, therefore the
    environment of the two babies will differ
  • A piece of supporting research evidence comes
    from Belsky and Rovine (1987) who suggested that
    children with different temperaments present
    different challenges to their caregivers, these
    determine the caregivers response to them and
    these responses change the environment for that
    child. So two children brough up in the same home
    and same environment may in fact be creating
    their own uniquely different environments
  • These findings help to explain why some MZ twins
    who have been brought up in different families
    have been known to report their adoptive patents
    warmth as so similar they might be the same
    parents (Plomin, 1988, 1994)
  • The child creates its own microenvironment
    which is related to its innate characteristics.
  • Flanagan (2000) nature creates its own nurture
  • TASK You need to explain the information above
    to the rest of the class, you also need to
    include in your feedback what this information
    means for the research on twins for schizophrenia
    and mood disorders. How could this be used to
    evaluate such studies?

3
The interaction of heredity and the environment
Constructivism
  • Constructivism the view that human experience is
    a construction of reality. Individuals shape and
    actively create their own experiences.
  • The interaction of genetic and environmental
    factors has prompted some psychologists to coin
    the term of constructivism. This focuses on the
    idea that when talking about nature and
    nurture we cannot look at the environment
    independently of the person, because people
    attach their own meaning to events and
    experiences and may be seen as making their own
    environments
  • People shape and select environments well suited
    to their natures. As an example consider two
    sisters, reared together, one of whom is
    naturally more academic than the other. Each
    will make friends with those whom they feel
    comfortable and who share similar interests. The
    more academic sister will probably make friends
    with those who share her interests and are of a
    similar intellectual level and whom she finds
    intellectually stimulating. The other sister may
    feel uncomfortable in such an environment and
    will make friends with those who share her
    interests.
  • TASK You need to explain the information above
    to the rest of the class, in addition you should
    consider, of the approaches you have covered,
    what does the view of constructivism go against,
    and why?

4
Research study Blakemore and Cooper (1970)
  • Blakemore and Coopers study demonstrates that
    even the purely biological development of the
    nervous system turns out, on closer
    investigation, to involve the environment thus
    displaying the interaction between heredity and
    the environment
  • Aim to investigate the effects on perceptual
    processing of being reared in a restricted visual
    environment
  • Method newborn kittens were placed in drums that
    had either horizontal or vertical lines on the
    walls. The floor was made of glass reflecting the
    patterns of the stripes. The kittens were fitted
    with collars around their necks so that they
    could not see their own bodies. At 5 months the
    kittens were tested for line recognition.
  • Results those who had been brought up in the
    vertical world acted as if blind to a
    horizontal world for example, they would trip
    over ropes. Conversely, those brought up in a
    horizontal world acted as if blind to a
    vertical world for example, they would walk into
    chair legs. This behavioural blindness was
    supported by physiological blindness.
    Microelectrode recordings confirmed that the
    cells in the visual area of the brain only showed
    an electrical response top the orientation
    experienced by the kitten.
  • Conclusion such findings suggest that the
    environment is important to the development of
    innate systems
  • Evaluation the study has been criticised on
    ethical grounds
  • TASK You need to explain the information above
    to the rest of the class as well as considering
    what additional evaluation points exist for this
    study

5
PKU
  • Phenylketonuria (PKU) is an inherited disorder
    and a classic example of the interaction between
    heredity and the environment
  • People with PKU are unable to metabolise
    phenylalaline (a protein contained in many
    everyday foods)
  • In people with PKU phenylalaline is broken down
    into a substance which is poisonous to the
    developing nervous system, resulting in brain
    damage and intellectual retardation
  • Genetic factors are strongly implicated as the
    problem can be traced to a pair of defective
    genes
  • However, if the disorder is identified soon after
    birth and the child is brought up on a
    phenylalaline free diet, development is normal.
  • So although PKU is hereditary it is not possible
    to separate nature and nurture. We cannot say,
    for example, that in someone with PKU genetic
    factors caused low intelligence, neither can it
    be claimed that the environment caused low
    intelligence
  • TASK You need to explain the information above
    to the rest of the class. Consider the terms
    genotype and phenotype can these be applied
    to an example to provide a further case of it
    being impossible to separate nature and nurture?
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