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 individual’s 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 caregiver’s 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 it’s 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 Cooper’s 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?