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Biological Area: Blakemore and Cooper (1970) - Brain Development in Cats Background information This study is about how the brains of kittens can change depending on their early visual experiences. We already know the different types of vision. We study cat vision because they are intelligent animals. They can learn, solve problems and adapt to their environment similar to what a human can do. Tufts University proved that cat and human brains are very similar. They both have cerebral cortices with similar lobes, both have surface folding and both have grey and white matter. Previous research by Hubel and Weisel found that in a normal cat, neurones in the visual cortex respond to light and specific features of their visual world. They found that one type of neurone is orientation specific. It also proved that cat vision is binocular. They also found that total visual deprivation in kittens causes neurones in the brain that should be associated with the eyes to decline in number. Hirsch and Spinelli found that early visual experiences can change neuronal organisation in kittens, when they reared them wearing special goggles that made one eye view vertical stripes only and the other with horizontal stripes only. Blakemore and Cooper began a related project to Hirsch and Spinelli and the study is a preliminary report of their findings. Their study is slightly as they allowed the kittens to have normal binocular vision in an environment consisting of only horizontal or vertical stripes. They did not use goggles. Key definitions Visual tracking: The ability to follow the path of a moving object. This is normally a smooth and accurate process using the eyes or head. Cats use this when they are chasing a toy. Depth perception: The ability to judge the position of an object to establish how far away it is. This ability is very useful and helps us daily from being able to drive, catching things that are thrown to us to being able to walk downstairs. Monocular vision: Means ‘one eye’ and is when certain cells respond to information from only one of the two eyes. It can be used to refer to vision or to properties such as cells that are monocular. Binocular vision: Refers to both eyes and an action that uses both eyes, such as reading a book. Aim The aim was to investigate the development of the primary visual cortex (vision area of the brain) in cats and to find out if some of its properties such as orientation selectivity are innate (like Hubel and Weisel suggest) or are learned. Participants Kittens were studied from birth and were raised in darkness until the report was completed. The number of kittens raised in the dark is unknown. 2 kittens were randomly allocated after 2 weeks to one of two conditions (vertical or horizontal). One kitten was raised in a horizontal condition and the other was raised in a vertical condition and were used to study neurophysical effects. All kittens were raised in darkness for at least 2 weeks and the two being raised in other conditions were taken out to spend time in their other conditions after 2 weeks. Research method and design This was a lab experiment because the whole experiment took place in a lab under strict control and you were manipulating the independent variable. It used independent measures design because the kittens were raised in one of two conditions (vertical or horizontal) and they couldn’t use the same kitten for both conditions else the experiment wouldn’t work.

IV DV Whether the kittens were reared in a horizontal or The kittens visuomotor behaviour once they were vertical condition. placed in an illuminated environment (whether the horizontally raised kittens could detect vertically aligned objects and vice versa). Materials Kittens; vertical condition; horizontal condition; apparatus was cylindrical in shape and there was a glass platform where the kitten was placed; wide black collars; high contrast black and white stripes; lid placed on top. Procedure From 2 weeks old, the kittens were put into special apparatus for an average of 5 hours per day. The kitten stood on a clear glass platform inside a tall cylinder. The entire inner surface was covered with high contrast black and white stripes. The stripes were either horizontal or vertical. There were no corners or edges and the upper and lower limits of the stripes were high enough so the kitten could see the end of the lines. They wore a black collar which restricted their view to a width of 130 degrees and stopped them from being able to see themselves. The routine stopped when the kittens were 5 months old because beyond 5 months is past the critical period in which visual deprivation causes physiological deficits according to Hubel and Weisel. After this period, for several hours each week, the kittens were taken from their dark cages to a small, well lit room, furnished with tables and chairs. Their visual reactions were observed and recorded in this room and at 7.5 months old, two of the kittens were anaesthetised so their neurophysiology could be recorded. Controls The size and shape of the visual apparatus; what the kitten could see other than the visual apparatus; the black collar; the time spent in the visual apparatus; the age when they were introduced to the visual apparatus; design of the visual apparatus (not the stripes); age when they were anaesthetised. Results Regardless of whether the kittens had been exposed to horizontal or vertical stripes, they were initially visually impaired: they guided themselves mainly by touch, they were frightened when they reached the edge of the table they were standing on, they showed no startle response when an object was thrust towards them and they showed ‘behavioural blindness’ in that kittens raised in the horizontal condition could not detect vertically aligned objects and vice versa. They recovered quickly and were able to develop some depth perception. Some defects were permanent such as the jerky head movements and distorted depth perception. There was no evidence of severe astigmatism which shows that it wasn’t an eye problem causing these responses. 75% of cells in both kittens were clearly binocular and responses were the same as a normal kitten. The distributions of preferred orientation were however totally abnormal and their neurones responded differently than normal but were not absent or inactive. Conclusions Visual experiences in the early life of kittens can modify their brains and have profound perceptual consequences. A kitten’s visual cortex may adjust itself during maturation to the nature of its visual experience. Brain development is determined by the functional demands made upon it, rather than preprogrammed genetic factors (not innate). The environment can determine perception at both a behavioural and physiological level (at least in cats, generalising to humans is questionable). Cells that began with a preferred vertical orientation changed to a horizontal preference when the environment presented was only horizontal.

Evaluation (add context to your point) Strength

Research Method

High control Lab experiment Generalizable to other kittens of the same breed Can see cause and effect

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One breed of kittens tested Only 2 tested

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Both types of data collected Scientific quantitative Qualitative data were from observations

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Not detailed quantitative data collected Not a lot of data for the length of time of the study

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High internal validity High face validity Extraneous variables controlled High control so conclusions accurate

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Lack of ecological validity Different for a human Lack of evidence Other breeds?

Replicable Standardised High control Lack of extraneous variables Consistent results

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Data not reliable to compare with a human Only 2 tested Only one breed

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Data Type

Validity

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Reliability

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How it is

Ethical Issues?

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Sampling Bias

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 Ethnocentrism

Weakness

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How it isn’t

Can’t give informed consent Used as few kittens as possible As little pain and distress inflicted No alternative Used best species

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Could be considered unethical Could have been painful No protection Didn’t even get data that could link to a human

Can be generalised to humans to an extent Most likely normal kittens Raised from birth so full control

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Only 2 tested in conditions Kittens and humans aren’t exactly the same One breed of kittens Not very generalizable Bred for research so could have been different

Human brains are different than kittens Different breeds Culture influences human brains

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How does Blakemore and Cooper link to the key theme

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Proved that they are similar

Brain plasticity refers to the ability to change the size and shape of the brain. We know that the human hippocampus has the ability to generate new cells throughout life. Blakemore and Cooper investigated whether kittens raised in an environment of vertical or horizontal stripes would develop normal vision. It was about how the brains of kittens can change depending on their early life visual experiences. Blakemore and Cooper found that at first, the kittens guided themselves mainly by touch and showed behavioural blindness. This proves that visual experiences in the early life of kittens can modify their brains and have profound perceptual consequences. How does Blakemore and Cooper link to the biological area The biological approach attempts to explain human behaviour through an understanding of biological and neurological processes. This approach assumes that all behaviour has a biological basis, meaning all behaviour can be explained by our biology. Blakemore and Cooper were investigating how the brains of kittens can change depending on early life visual experiences. They wanted to see if kittens raised in an environment of vertical or horizontal stripes would develop normal vision. This links to the biological approach because it shows that early experiences can affect vision. Therefore, vision has a biological approach....