Psychology - How do we see our world?


Vision and Perception

  • Vision - the biological process of seeing
  • Perception - psychological process of making sense of the image
  • The light reflected from an object enters the eye and makes an image on the retina (at the back of the eye) where rods (light-sensitive cells that respond even in dim light) and cones (light-sensitive cells that can detect colour) help us perceive objects
  • The optic nerve carries the nerve impulses from the rods and cones to the brain
  • The blind spot is found in each eye, at the retina, where there are no rods or cones and we don't notice our blind spot because our two blind spots don't overlap so if one eye can't see something, the other one can
  • The optic chiasma is needed because information from each eye goes to both sides of the brain; some from the left eye goes to the left side of the brain and some to the right side
  • The visual cortex allows us to understand shapes and distances and fills in the gap left by the blind spot in each eye

Depth Cues

  • We can judge depth in the real world and we can understand depth in pictures by the use of depth cues which are pieces of visual information that 'cue' our understanding of distance 
  • Size constancy - when we look at an object that is close our brain scales it down so that it looks normal sized and when an object is further away we scale it up so it looks normal rather than tiny and this reminds us that the size of the object remains constant but helps us to make sense of our world 
  • Monocular depth cues - information about distance that comes from one eye, such as superimposition, relative size, texture gradient, linear perspective and height in the plane
  • Relative size - we perceive bigger objects as being closer than smaller objects
  • Texture gradient - when looking at cobblestones or a sandy beach we see that close up the surface is very detailed while further away the texture is less clear
  • Height in the plane - when we look at pictures that include the horizon, objects lower in the scene appear closer than those objects higher up which appear further away
  • Superimposition - objects in front of or partly covering other objects are closer to us
  • Linear perspective - very long straight roads and railway lines appear to converge in the distance, even though we know they don't
  • Binocular depth cues - information about distance that needs two eyes, such as stereopsis
  • Stereopsis - allows us to see one image when we are presented with two images side by side, one from our left eye and one from our right eye, forming one perception from the two images in our brain - the image on the right retina and the image on the left retina are combined and when we are looking at something far away, the two images are very similar while when we


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