Summary of the Study
Aims = To investigate the physiological and behavioural effects of a limited visual experience and whether brain plasticity occurs due to experiences rather than nature.
Sample = Ps = new born kittens who were immediately placed into a dark room. At 2 weeks of age the kittens were then randomly placed into one of two conditions for 5 hours a day.
Method
This study was a laboratory experiment. IV = horizontal or vertical environment.
The kittens had to stand on a clear glass platform which was inside a tall cylinder of which the inner surface was covered with either horizontal or vertical black-and-white stripes. The kittens’ visual field was restricted to 130 degrees, as they were required to wear a wide black collar. This prevented them from seeing their own body and ‘beyond their world of stripes’.
After 5 months, the kittens were then placed for several hours a week from their dark cage to a small, well-lit furnished room. DV was then measured: whether kittens raised in a horizontal environment could detect vertically aligned objects and vice-versa. After 7 and a half months, two of the kittens, one from each environment were anaesthetised and their neurophysiology was examined.
Results
There was recovery from their early deprivation. After 10 hours the kittens showed visual placing and some startled responses; they could also easily jump from a chair to the floor. But the kittens did suffer some permanent damage such as trying to touch things well beyond their reach and following objects with clumsy head movements. The neurophysiological exam found evidence that horizontal plane recognition cells did not ‘fire-off’ in the kitten from the vertical environment and vice-versa.
Conclusion
Brain development is affected by early experiences and environmental factors rather than just genetics and there is clear evidence of brain plasticity – ‘the visual experience of these animals had modified their brain’ and therefore has serious perceptual consequences. The kittens’ visual cortex adjusts during development as a result of its visual experiences.
Evaluation: Research method
As this was a laboratory experiment, the kittens’ environments were highly controlled and therefore causal conclusions can be made. The study has levels of internal validity - we can infer that the IV (environment) caused visual impairment and neurophysiological damage (DV). The study could also be easily replicated in order to test the reliability of the findings (although this wasn’t done).
Evaluation: Ethical considerations
Exposing animals to a dark room for 2 weeks and in a visually depriving environment until 5 months is psychologically harmful for the kittens. However, B&C reported no distress from the animals. Furthermore, the study complied with the ethical guidelines for animal research. It could also be argued that any harm to the animals were outweighed by the usefulness of this research.
Evaluation: Sampling bias
B&C would argue that due to some physiological similarities between cats and humans, we can generalise results to humans. But, critics would argue against this due to obvious differences between the species. Also, as the sample was small (2 cats) we may not be able to generalise to other cats.
Sample = Ps = new born kittens who were immediately placed into a dark room. At 2 weeks of age the kittens were then randomly placed into one of two conditions for 5 hours a day.
Method
This study was a laboratory experiment. IV = horizontal or vertical environment.
The kittens had to stand on a clear glass platform which was inside a tall cylinder of which the inner surface was covered with either horizontal or vertical black-and-white stripes. The kittens’ visual field was restricted to 130 degrees, as they were required to wear a wide black collar. This prevented them from seeing their own body and ‘beyond their world of stripes’.
After 5 months, the kittens were then placed for several hours a week from their dark cage to a small, well-lit furnished room. DV was then measured: whether kittens raised in a horizontal environment could detect vertically aligned objects and vice-versa. After 7 and a half months, two of the kittens, one from each environment were anaesthetised and their neurophysiology was examined.
Results
- All the kittens were extremely visually impaired
- they demonstrated no visual placing when put on a table top
- they had no startle response when an object was thrust towards them
- their papillary reflexes were normal and they guided themselves mainly by touch
- All kittens showed behaviour blindness - they could not detect objects or contours that were aligned in the opposite way to their previous environment.
- They showed fear when standing on the edge of a surface.
There was recovery from their early deprivation. After 10 hours the kittens showed visual placing and some startled responses; they could also easily jump from a chair to the floor. But the kittens did suffer some permanent damage such as trying to touch things well beyond their reach and following objects with clumsy head movements. The neurophysiological exam found evidence that horizontal plane recognition cells did not ‘fire-off’ in the kitten from the vertical environment and vice-versa.
Conclusion
Brain development is affected by early experiences and environmental factors rather than just genetics and there is clear evidence of brain plasticity – ‘the visual experience of these animals had modified their brain’ and therefore has serious perceptual consequences. The kittens’ visual cortex adjusts during development as a result of its visual experiences.
Evaluation: Research method
As this was a laboratory experiment, the kittens’ environments were highly controlled and therefore causal conclusions can be made. The study has levels of internal validity - we can infer that the IV (environment) caused visual impairment and neurophysiological damage (DV). The study could also be easily replicated in order to test the reliability of the findings (although this wasn’t done).
Evaluation: Ethical considerations
Exposing animals to a dark room for 2 weeks and in a visually depriving environment until 5 months is psychologically harmful for the kittens. However, B&C reported no distress from the animals. Furthermore, the study complied with the ethical guidelines for animal research. It could also be argued that any harm to the animals were outweighed by the usefulness of this research.
Evaluation: Sampling bias
B&C would argue that due to some physiological similarities between cats and humans, we can generalise results to humans. But, critics would argue against this due to obvious differences between the species. Also, as the sample was small (2 cats) we may not be able to generalise to other cats.
Lesson Materials can be found here
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