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?