chapter 6 - visual perception Flashcards
sensation and perception
- reception
- transduction
- transmission
- selection
- organisation
- interpretation
- reception
light enters eye through cornea, then passes through the pupil. the lens focuses the light on the retina, which contains photoreceptors (rods and cones)
- transduction
the electromagnetic energy (light energy) is converted by rods and cones into electrochemical nerve impulses.
- transmission
rods and cones send the nerve impulses along the optic nerve to the primary visual cortex in the occipital lobes (back of brain), where receptor cells respond
- selection
image is broken up by feature detectors, so that we can pay attention to the important stimuli.
- organisation
when visual info reaches the brain, it is recognised so that we can make sense of it by using perceptual principles. once reassembled, it travels along two pathways simultaneously, to temporal lobe and parietal lobe.
- interpretation
visual stimulus is given meaning. the temporal lobes identify what the object is by comparing incoming info with info already stored in memory.
perceptual constancies
enable us to maintain a stable perception of a stimulus, although image on retina may change.
size - we maintain a constant perception of an object’s size, even if the size on the retina alters.
shape - object is perceived to maintain its known shape despite the changing perspective from which it is observed.
gestalt principles
- figure-ground organisation
- camouflage
- closure
- similarity
- proximity
closure
we perceive an object as being whole, despite it being incomplete.
proximity
the individual parts of a stimulus pattern are close to each other, we tend to group them together as a meaningful ‘whole’.
camouflage
where figure-ground is used to ‘blend’ the contour of the figure against the ground, making the figure more difficult to see.
figure-ground organisation
organising the part of the visual field which we focus on, the figure, and the background, the ground, by an imagined contour.
similarity
an individual parts of a stimulus pattern are similar, we tend to group them together as a ‘whole’
depth perception
ability to accurately judge 3D space and distance, using cues in the environment.
binocular depth cues (two eyes)
retinal disparity: as our eyes are separated, each eye receives a slightly different image on the retina.
convergence: as an object comes closer to us, our eyes turn inwards to keep the object centred on the retina.
monocular depth cues (one eye)
accommodation: lens of the eye changing shape so that it can focus light rays onto the retina.
pictorial depth cues
- linear perspective
- interposition
- texture gradient
- relative size
- height in the visual field
linear perspective
parallel lines are made to converge as they extend along the page to an imaginary point.
texture gradient
used to make surfaces in a picture appear to recede into the distance (less and less detail as an image is more distant)
interposition
is based on the partial blocking or obscuring of one object by another, the obstructed object appears to be further away.
relative size
based on our tendency to perceive the object producing the largest retinal image as being nearest.
height in the visual field
shows depth by portraying object further away as being closer to the horizon.
perceptual set
a predisposition to perceive stimuli in a specific way. can be affected by: - emotion - motivation - context - previous experience
visual illusion
occurs when perception consistently differs from the objective reality. types: - ponzo illusion - muller-lyer illusion - amens room illusion
visual perception`
how light from an object is cast as an image on the retina and nerve impulses travel to the brain where higher mental processes enable us to interpret what we see
