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Psych109 Vision
Vision
| Question | Answer |
|---|---|
| What was the belief of John Locke in terms of brain development? | At birth, the mind is a blank slate |
| What was the belief of Aristotle in terms of brain development? | Natural philosophy |
| Amplitude | Important determinate of perceived brightness |
| Wavelength | Important determinate of perceived colour |
| Myopia | Nearsightedness. Difficulty focusing on distant objects. Caused by eyeball that is too long to focus on the image of the retina properly. Corrected by glasses or contacts which focus image correctly on retina |
| Hypermetropia | Farsightedness. Difficulty focusing on near objects. Eyeball is too short, or lens is too thin. |
| Rods | More numerous (about 120 million) and sensitive than cones. Cannot see colour. |
| Cones | Less numerous than rods (about 6 or 7 million). Colour sensitivity. Concentrated in the macula. |
| Fovea | Center of macula. Responsible for central, sharpest vision. Detail. high concentration of cones. Quite small. About area of thumbnail at arms length. 1 degree to 2 degrees. |
| Why are we not aware of a blind spot if we close one eye? | The brain seems to automatically 'fill in' gaps when we close one eye. This was discovered by V.S. Ramachandran when he conducted an experiment. |
| What is the ratio of dimmest perceptible object to extremely bright object? | 1:100,000,000,000 |
| Duplex theory of vision ‒ rods | Specialised for night-time (scotopic) vision Difficult to discriminate colour at night (achromatic sensation) Difficult to discriminate fine detail at night – poor acuity Retina contains about 120 million rods. No rods in Fovea. Increases in peripheral |
| Duplex theory of vision ‒ cones | Cones are specialised for daytime (photopic) vision. Responsible for colour vision. Foveal vision – The fovea has ONLY cone receptors. There are no rod receptors in the fovea. The density of cones decreases in peripheral vision. |
| Duplex theory of vision ‒ Photopic vision | Normal daylight Seeing with cones and rods High acuity (fine detail), but low sensitivity |
| Duplex theory of vision ‒ Scotopic vision | Dark adaptation (slow – about 30mins) Seeing with rods High sensitivity, but low acuity (loss of fine detail) |
| Purkinje shift | Change in the apparent brightness of colours with changing light levels. Swap from Photopic vision to Scotopic vision or vice versa. |
| Visual pigments ‒ Rods | The light sensitive visual pigment in the rod photoreceptors is (helpfully) called rhodopsin When photon(s) of light are absorbed by rhodopsin molecules a cascade of physical and chemical changes occur which cause the photoreceptor to fire. |
| Visual Pigments ‒ Cones | Cones have three different visual pigments. |
Created by:
clea528
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