biological : blakemore and cooper

aim

• to limit the visual experience of a kitten to one orientation (horizontal or vertical stripes) to study the neurophysiological effects on the neurones in the kittens visual cortex

method and design

• lab experiment

• independent measures

sample

• several kittens were raised from birth in either the horizontal or the vertical condition (random allocation)

• 1 horizontally reared kitten and 1 vertically reared kitten used to look at the effect on their neuron’s

variables

• IV : whether the kittens were reared in a vertical or horizontal environment

• DV : visuomotor behaviour in the illuminated environment (whether the horizontally raised kittens could detect vertically aligned objects, also neurophysiological changes)

procedure

• from birth - 2 weeks → kittens in a completely dark room

• 2weeks - 5months → placed in an illuminated cylinder (no edges or corners)

• exposed to either only horizontal stripes or only vertical stripes for 5 hours a day

• cats were a collar to tunnel their vision

• after 5months (‘critical period’ for visual development) removed from dark room and placed in well-lit and furnished room

• visual reactions observed and recorded

• after 7.5months, 2 cats neurophysiology was examined

observation results

• all cats were visually impaired - no startle response / reflexes

• could only guide themselves by touch / frightened ‘behavioural blindness’

• occurred when the cats were exposed to the opposite orientation (e.g. those that were in verbal couldn’t detect a rod travelling horizontally)

• but after 10 hours of normal vision, cats showed signs of recovery including the ‘startle response’

• but some defects were permanent including the clumsiness and spacial awareness difficulties

neurophysiological examinations results

• distributions of neurones was abnormal - vertical environment cats lacked neurones in horizontal position (physical blindness)

• in comparison to normal cats, there were similarities in that vision is binocular and differences in neurone distribution

conclusions

• visual experience in the early life of kittens can modify their brains and has profound perceptual consequences

• a kittens visual cortex may adjust itself during maturation to its visual experiences, cells can show preference when the visual environment is manipulated

• brain development is a product of functional demands rather than pre-programmed genetic factors (environmental, nature and nurture)

• supports brain plasticity in cats but is difficult to apply to the human brain

sampling bias

• small sample

• only 2 used for neurophysiological examination

• cats are not humans so can it be generalised?

validity

• good internal as high levels of control

• low external as oversimplified environment, not realistic

ethics

• not ethical

• not protected from harm - had electrodes out in their heads, taken away from their mothers, were in isolated chambers, permeant visual impairments caused

• no pain caused and minimum number used for neurophysiological examining (2)

• suffering compared to importance and benefit of research

research method

• lab experiment

• standardised procedures

• high level of control

• scientific equipment used

type of data

• both types of data collected

• quantitative - neurons active or not

• qualitative - behavioural observations

reliability

• high internal as can repeat as standardised procedures used

• tested many neurons which showed the same patterns

practical applications

• critical period when younger

• can apply to humans (both mammals)

• understanding / fixing visual impairments when younger, importance of visual cortex developing

ethnocentrism

• not relevant in this study