blackemore and cooper

• BLAKEMORE AND COOPER: THE IMPACT OF EARLY VISUAL EXPERIENCE BIOLOGICAL PSYCHOLOGY
• Biological area assumptions


  • Behaviour can be largely explained in terms of biology – genes, neuroanatomy, neurochemicals etc have a direct influence on behaviour
  • Psychology should be seen as a science, to be studied in a scientific manner (usually in a lab) measuring variables objectively, eg MRI scans
  • The biological approach focuses on how nature rather than nurture influences us
• Plasticity


  The brain's ABILITY to adapt
• Plasticity


  • Can be positive e.g. learning a new experience
  • Can be negative e.g. trauma (RTA)
• When we are born, our early experiences in the environment shape us to be who we are. E.g. Parents voices can be associated with the baby with the feeling of safety. After 3 months of being born, the baby normally can recognize faces.
• As humans, our brains are the most complex out of any animal we are aware of on earth. However, according to some research the brain structure of some animals are very similar including cats.
• Previous research suggests cats have visual recognition memory and neuroplasticity and the development of spatial perception in the early environment depends on the visual environment that they experienced.
• In normal cats, the neurons of the visual cortex are selective of lines and edges in the visual field which simply means they can recognise which direction lines and outlines of objects are facing when they look at them however a study found that this can be changed depending on the cats early visual experience.
• Hirsch and Spinelli in 1970 investigated a group of newborn kittens with one eye viewing vertical stripes and the other eye viewing horizontal stripes and found that out of 21 neurons with elongated receptive fields all were monocularly (single eye) driven and in all but one case the orientation of the receptive field closely matched the pattern experienced by the eye.
• Blakemore and Cooper investigated this further with a slightly different approach to find out more about how cat's visual environment can affect the development of their visual cortex
• Monocular vision


  Vision in which each eye is used separately
• Binocular vision


  Vision in which both eyes are used together
• The sample were two kittens raised in a laboratory environment, housed in complete darkness until 2 weeks of age.
• They were randomly allocated to one of the two conditions (one reared in a horizontal and one in a vertical environment) were used to study neurophysiological effects
• The cats were 5 months old during the behavioural tests and 7.5 months old at the time of the neurological tests
• Materials


  A special cylinder was constructed where a kitten stood on a clear glass platform inside a tall cylinder the entire inner surface of which was covered with high contrast black-and-white stripes, either vertical or horizontal. There were no corners to its environment, no edges to its floor and the upper and lower limits to its world of stripes were a long way away.
• Early experience

  1. For the first 2 weeks the kittens were raised in a completely dark room (allowed binocular vision: both eyes)

  2. From the age of two weeks they were put into a special apparatus for an average of about five hours per day (the rest of the time they were in a dark room)
• Exposure to normal environment


  1. The visual deprivation routine was stopped when the kittens were 5 months old

  2. The kittens were now cat's and their visual systems were fully developed-they were passed the critical period during which changes can take place to the biological visual system

  3. The kittens were then taken for several hours each week from their dark cage to a small, well-lit room, furnished with tables and chairs

  4. The cats were given artificial lenses to ensure that any visual difficulties were not due to stigmatism which causes blurred vision (and which may have acted as an extraneous variable)
• Testing

  1. Behavioural assessment: The cat's initial responses to the new visual world were observed and recorded before any learning could take place

  2. Further observations were made over the following weeks as they learned to "see" the new visual environment i.e whether kittens raised in a horizontal environment could detect vertically aligned objects and vice versa

  3. Neurophysiological assessment: At 7.5 months, two of the kittens (one reared in the horizontal and one reared in the vertical environment) were anaesthetised and temp paralysed so the responses of individual units (columns of neurons in their visual cortex) could be tested using an electrode inserted into the unit (micropipette). The measures of electrical firing of each individual neuron.

  4. The cats eyes were shown lines of all possible orientations "around the clock" to test what neurophysiological responses there were
• Blakemore and Cooper


  Biological area
• Blakemore & Cooper


  Key area (plasticity)
• aims

  • investigate the effect on kittens' visual development of a restricted visual environment consisting of either vertical or horizontal stripes only, in which the animal could move freely
  • to investigate the development of the primary visual cortex to see if orientation selectivity are innate or learned
• findings


  regardless of if kittens were exposed to vertical or horizontal, they were initially visually impaired

  pupillary reflexes were normal but showed no visual placing when brought up to the table and no startle when an object thrusted towards them
• findings


  • they guided themselves through touch
  • frightened when they reached the edge of a surface they were stood on
• conclusions


  • visual experiences in the early life of kittens can modify their brains and have profound perceptual consequences
  • a kittens visual cortex may adjust itself during maturation to the nature of its visual experience
• conclusions

  • a kittens nervous system adapts to match the probability of occurrence of features of its visual input
  • brain development is determined by the functional demands made upon it, rather then pre-programmed genetic factors
• ethics


  pain and distress from the invasive procedure-> kept in dark for a long period of time and being separated from mother during testing
• internal validity


  lab exp. allow control over variables and conditions to find cause and effect easier-> could control the vertical or horizontal environment the kittens were in
• ecological validity


  dark room and horizontal/vertical environment not real life condition for the kittens
• external validity


  kittens visual structures closely resemble humans therefore appropriate models
• reliability


  standardised conditions in a lab experiment, kittens had same experience in each condition apart from the vertical or horizontal environment allowing replication and consistency across different studies