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Chapter 5

PSYA01H3 Chapter Notes - Chapter 5: Opponent Process, Color Vision, Trichromacy


Department
Psychology
Course Code
PSYA01H3
Professor
Steve Joordens
Chapter
5

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1 vergence movements: co-operative movements that keep both eyes fixed on the same
target
2 saccadic movements: rapid movement of the eyes make to maintain an image of a moving
image upon the fovea
There are 3 types of cones in the human eye, each containing a different type of
photopigment
Hue of a colour is determined by wavelength (ex: 540 nm = green)
A colours brightness is determined by the intensity, or amount of energy, of the light that is
being perceived
Third perceptual dimension of colour, saturation is roughly equivalent to purity (fully
saturated colour consists of only one wavelength -> I.E. pure red)
Vision = a synthetic sensory modality (synthesizes [puts together] rather than analyzes
[takes apart] auditory system is analytical
Colour mixing: perception of two or more lights of different wavelengths seen together as
light of an intermediate wavelength
Thomas Young (1802)
Human visual system can synthesize any colour from various amounts of almost any set of
3 colours of different wavelengths
Proposed trichromatic theory of colour vision eye contains 3 types of colour receptors, each
sensitive to a different hue (blue, green, red) and that the brain synthesizes colours by
combining the information received by each type of receptors.
Edwald Hering noted that the four primary hues appeared to belong to pairs of opposing
colours: red/green, yellow/blue -- WRONG
Two types of ganglion cells encode colour vision: red/green cells, and yellow/blue cells
Both types of ganglion cells fire at a steady rate when they are not stimulated
The brain learns about the presence of red or green light by the increased or decreased rate
of firing of axons attached to red/green ganglion cells
Opponent process: representation of colours by the rate of firing of two types of neurons:
red/green and yellow/blue)
We cannot perceive a reddish green or a bluish yellow
www.notesolution.com
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