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Blakemore & Cooper 1970 (Evaluation (Psychology as a science:…
Blakemore & Cooper 1970
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Aims
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To investigate some of the properties of the visual cortex, such as orientation selectivity, to see if they are innate or learned
Methodology
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Dependent variables: Visiomotor behaviour in their normal environment and neurophysiology of two kittens in their visual cortex
Sample
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2 kittens (1 exposed to only vertical lines, the other only exposed to horizontal lines) were examined neurophysiologically
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Generalisation to humans: Both have cerebal cortices (visual cortex), both have similar lobes (occipital lobe) and both are gyrencephalic (surface folds and grey/white matter)
Procedure
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Placed in a 2 metre high cylinder with either horizontal or vertical lines for an average of 2 hours a day. The kittens wore a collar allowing 130 degrees of vison
At 5 months, the kittens were observed in their normal environment for several hours a week
At 7.5 months, 2 kittens were anaesthetised so they could have their neurophysiology examined using microelectrodes on 125 neurons in the visual cortex
Background
Hubel & Wiesel (1962):Found there are neurons that are orientation specific and that neurons in the visual cortex responded to more than just light
Hubel & Wiesel (1970): Rearing kittens in darkness causes neurons in the brain that should be associated with the deprived eyes to decline in number
Hirsch & Spinelli (1970): After kittens wore a mark so that one eye only saw vertical lines and one eye only saw horizontal lines, the neurons became exclusive to either vertical or horizontal lines and became monocular
Results
Normal: Pupils responded to bright light, no evidence of astigmatism, 75% of neurons were binocular
Temporary defect: No visual placing, no startle response, moved mainly by touch, frightened when on edge of object
Permanent defect: Bumped into stationary objects, followed objects clumsily, made jerky head movements, poor at judging distances, only responded to orientation of lines exposed to
Neurophysiological: 75% neurons remained binocular, no neurons had a preferred orientation within 20 degrees of the opposite orientation to which they were exposed, only 12 neurons had a preferred orientation within 45 degrees of the opposite orientation to which they were exposed
Evaluation
Psychology as a science: Manipulation of IVs and scientific equipment used (microelectrodes) but collected qualitative data
Usefulness: Shows need to stop mistreatment early, shows need to identify problems early, and shows there is a critical period
Nurture/Situational explanations: Brain can change depending on environment (brain plasticity) due to the orientation of lines
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Ethical considerations: No consent, permanent harm to kittens
Validity: Standardised/laboratory experiment (internal), but collected qualitative data (internal) and sample only consisted of kittens (population)
Reliability: Highly standardised/replicable (internal) but collected qualitative data so as easily replicable (subjective) (internal)
Sampling bias: Sample included both males and females but only consisted of kittens so may not be generalisable to humans
Conclusions
Visual experiences in the early like of kittens can modify their brains and have profound perceptual consequences
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A kitten's nervous system does adapt to match the probability of occurrence of features of its visual input
Brain development is determined by the functional demands made upon it, rather than pre-programmed genetic factors
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