Blakemore and Cooper

• Background

  Blakemore and Cooper were inspired by the process of brain plasticity, which is when the grey matter of the brain changes both structurally and functionally, functionally in terms of strengthening or weakening of neural pathways.

  
  

  They were particularly interested in the brains of kittens, as there was evidence that their brains adapt to the environment that they are in and their grey matter has a similar structure to that of humans.

  
  

  Research by Hirsch and Spinelli showed that early visual experiences can change the orientation of the visual cortex of kittens and testing this using a monocular method findings neural pathways were weakened in one eye.

  
  

  Blakemore and Cooper wanted to expand on this by doing a binocular study in which the kittens experienced either a horizontal or vertical environment with both eyes to see if this would cause the brain to plasticise.
• Aim

  To investigate the development of the primary visual cortex and to find out if some of its properties such as orientation selectivity are innate or learned
• Sample

  - 2 kittens were randomly allocated to one of two conditions (one raised in a horizontal environment and one raised in a vertical environment

  - kittens were in critical period of their lives from 0-3 months
• Research method

  - lab experiment with an independent measures design

  
  

  - IV = horizontal or vertical stripes

  - DV = measuring behavioural and physical blindness
• Procedure

  - kittens were housed from birth in a completely dark room

  - from age of 2 weeks, put in a specialist device for 5 hours a day

  - entire surface of cylinder was covered in high contrast black and white stripes which were either vertical or horizontal

  
  

  - routine was stopped when kittens were 5 months old (beyond critical period where visual deprivation causes physiological deficits)

  - kittens were taken for several hours a week from their dark cages to a small well-lit room where their visual and physical reactions were recorded

  
  

  - at 7.5 months, two kittens (one raised in vertical + one raised in horizontal environment) were anaesthetised so their neurophysiology could be examined
• Outline 2 controls used in the procedure and explain why they were used (4)

  - kittens were housed from birth in a completely dark room to ensure they weren't exposed to any other environment that could affect their visual cortex

  - both kittens wore a black collar which restricted their view so can only see stripes

  - exposed to cylinder for 5 hours per day after the age of 2 weeks = limits other effects

  
  

  WHY - in order to isolate the IV and establish cause + effect
• behavioral findings - qualitative

  1) 'behavioral blindness' = kittens raised in the horizontal environment could not detect vertically aligned objects

  both sets of kittens remained blind to perpendicular contours to the stripes they had lived with

  
  

  2) horizontally raised kittens failed to see vertical stripes
• physiological findings - quantitative

  1) physical blindness occurred as certain cells were not firing (change in neural pathways)

  
  

  2) in a normal cat, the pattern of visual neurons would be balanced however kittens from this study did not show the same neural pattern
• Conclusions

  1) visual experiences in the early life of kittens can modify their brains and show brain plasticity

  2) a kittens visual cortex may adjust itself during the critical period to the nature of its visual experience

  3) the environment can determine perception at both a behavioural and physiological level (environment can change how innate neurons of the visual cortex can demonstrate themselves)
• Link to biological approach

  The biological approach assumes that all behaviour has a physiological origin and is caused by genetics that we inherit, however, the way in which these genetics demonstrate themselves is due environmental experiences.

  Blakemore and Cooper link to the biological approach as their findings illustrate that the kitten's visual cortex plasticised due to the environment they were raised in.

  They were all born with a normal functioning visual cortex in which all contours were preferred and recognised, however, due to the horizontal or vertical environment exposure, the kitten's visual cortex changed and the neurons only preferred the contours they had been exposed to.

  This illustrates that their innate physiological factors were changed by their environmental experiences.
• Link to key theme of 'brain plasticity'


  Blakemore and Cooper researched the brain plasticity of the visual cortex of kittens based on their early visual experiences. (1) 2 kittens were used and kept in darkness from birth. (1)

  Then after a 2-week period, they were exposed to either a horizontal or vertical environment in a purpose made cylinder for 5 hours of the day until the age of 5 months which was past the critical period. (1)

  It was found that after this period, the kittens that were in the purely horizontal environment had no neurons firing that preferred vertical contours.

  This links to thekey theme of brain plasticity as the findings illustrate that the kitten's visual cortex plasticised to prefer the environment and visual contours that they had been exposed to. (1)
• Ethical issues (broken + followed)

  - follows principles of respect and responsibility

  - physical harm = cats demonstrated long lasting clumsiness as a result

  - psychological harm = environment they were raised in, may have been emotionally distressing for cats
• Reliability

  Internal:

  + highly standardised procedure

  -> eg. placed in a specialist device for average of 5 hours a day

  -> allows for replication

  
  

  External:

  + quant data collected

  -> eg physiological findings

  -> allows for consistency to be checked
• Validity

  + High internal validity = high control over EVs

  -> eg. kittens housed in complete darkness

  -> establish cause + effect between the restricted visual environment + blindness in kittens

  
  

  + high concurrent validity

  - > research measured both behavioural + physical behaviours of kittens raised in restricted environment + both measures concurred with each other

  -> supports claim that development of kittens brains has been influenced by the environment

  
  

  - low population validity

  -> sample of 2 kittens is not applicable to how other kittens might respond or how the human brain may plasticise
• Sample evaluation

  + somewhat representative of brain plasticity in humans

  -> brains of cats have similar structures to human brains

  
  

  - low population validity/generalisability to humans

  -> evidence from brains of cats so lacks generalisability to other animals

  -> cautious making claims about the environment + how it impacts brain development
• Nature v nurture

  Nature:

  -> kittens were born with neurons with a preferred orientation + with a fully formed visual cortex so this was innate

  
  

  Nurture:

  -> restricted + manipulated environment the kittens were raised in had a significant impact on how the visual cortex developed

  -> kittens visual neurons adapted to their environment which was learned
• Freewill v determinism

  Determinism:

  -> behavioural blindness was predetermined by the environment that kittens were raised in
• Usefulness

  Usefulness:

  -> enhances knowledge of functional brain plasticity + how the environment can influence the development of the brain during the critical period

  -> practical applications = educate students on the importance of exposing themselves to knowledge they will need in exams - avoid brain cells + neural pathways from weakening

  
  

  Limited usefulness:

  -> unrepresentative sample + lack of generalisability eg. sample consisted of 2 kittens during critical period = cannot generalise findings to human babies so limited applications
• Scientific

  Scientific:

  -> objective quantifiable measures used to measure brain plasticity in kittens eg. electrode was used to measure neurons firing in kitten visual cortex = allows scientific conclusions that cannot be misinterpreted

  -> high controls = ability to establish cause + effect between change in environment + impact on behavioural + physical blindness

  -> highly standardised = procedure can be easily replicated

  
  

  Unscientific:

  -> qualitative data may have been misinterpreted when measuring behavioural blindness to may have been subjective