Ch 2-4 Visual perception Flashcards
What are three major consequences when a visual stimulus reaches receptors in the retina:
reception, transduction and coding:
The amount of light entering the eye is determined by the pupil.
The lens adjusts in shape to bring images into focus on the retina.
Name the two types of visual receptor cells in the retina: .
cones and rods
What are rods and cones?
6 million cones, mostly in the fovea, which are specialised for colour vision and sharpness.
There are 125 million rods, which are specialised for vision in dim light and for movement detection:
The P (parvocellular) pathway
One of two optic tracts in the brain, sensitive to colour and detail, has most input from cones.
The “What” pathway
The M (magnocellular) pathway,
One of two optic tracts in the brain, sensitive to movement, has most input from rods.
The “How” pathway
Lateral inhibition is…
a reduction of activity in one neuron caused by activity in a neighbouring neuron.
It is useful because it increases the contrast at the edges of objects.
What are the 4 visual functions of the visual cortex
Form processing
Color processing
Motion processing
binding problem: putting form, color and motion together into perception
What are three main qualities of Color?
hue, brightness and
saturation.
Trichromatic theory describes three kinds of cone
receptors. Name them.
“blue: short-wavelength light
(yellow– green) medium-length
(orange–red): long-wavelength light
Other colours are perceived according to the
relative amount of stimulation of each cone type. If all three types of cones are activated, we see white.
Opponent processes theory says there are three color channels. Name them.
a red–green channel, which will perceive green when responding in one way and red when
responding in the opposite way;
a blue–yellow channel;
an achromatic (white–black) channel.
Dual-process theory
Hurvich and Jameson (1957) developed this theory as a synthesis of the trichromacy and opponent-process
theories.
Colour constancy
Colour constancy is the tendency for an object to appear the same colour when the wavelength of light illuminating it changes.
it is important to distinguish between our subjective
experience and our judgements about the world, which may change our perception of color.
There is no complete theory of how it really works.
Chromatic adaptation is….
when sensitivity to light of any given colour decreases over time.
What are 3 depth cues:
Monocular cues require only one eye.
Binocular cues need both eyes to work together.
Oculomotor cues rely on sensations from muscles around the eyes. (convergence and accomodation)
Convergence is when eyes turn..
inwards to focus on an object more for a close object than for one
farther away.
