Lecture 12 Flashcards
After showing participants a series of photos with implied motion to one side i.e. left or right for 60 seconds and asking them to identify the direction of movement in an array of moving dots.
Before being ‘adapted’ to the pictures participants were…
equally likely to perceive dots with zero coherence as moving to the right or left
After showing participants a series of photos with implied motion to one side i.e. left or right for 60 seconds and asking them to identify the direction of movement in an array of moving dots.
After being ‘adapted’ to the pictures participants were…
more likely to indicate an array of dots with zero coherence was moving in the direction OPPOSITE to which they had been adapted e.g. adapt to pictures with leftward motion, report seeing dots moving to right
colour helps us __ and ___ objects
colour helps us classify and identify objects
colour facilitates __ ___ of elements into objects
colour facilitates perceptual organization of elements into objects
participants were found to identify foods presented in ___ colours more rapidly
participants were found to identify foods presented in natural colours more rapidly
3 conclusions from Newton’s experiment with prisms
1) White light is a mixture of all colours
2) Other colours on the spectrum are not mixtures but rather represent ‘pure’ colours (cannot be broken down any further)
3) the fact that the degree to which beams from each part of the spectrum were ‘bent’ by the second prism differed was indicative of a difference in some physical property
___ colours (e.g. blue, green, red) are perceived when certain wavelengths are reflected by objects more than others i.e. ___ ___
Chromatic colours (e.g. blue, green, red) are perceived when certain wavelengths are reflected by objects more than others i.e. selective reflection
___ colours (gray, black, white) are perceived when light is reflected equally across the spectrum
Achromatic colours (gray, black, white) are perceived when light is reflected equally across the spectrum
Reflectance curves
plot percentage of light transmitted at each wavelength
Selective transmission
occurs when only certain wavelengths pass through objects, can be plotted with transmission curves
Short wavelength reflected or transmitted causes ___ to be perceived
Short wavelength reflected or transmitted causes blue to be perceived
Medium wavelength reflected or transmitted causes ___ to be perceived
Medium wavelength reflected or transmitted causes green to be perceived
Long and medium wavelengths reflected or transmitted causes __ to be perceived
Long and medium wavelengths reflected or transmitted causes yellow to be perceived
Long wavelengths reflected or transmitted causes __ to be perceived
Long wavelengths reflected or transmitted causes red to be perceived
Long, medium and short wavelengths together reflected or transmitted causes __ to be perceived
Long, medium and short wavelengths together reflected or transmitted causes white to be perceived
Subtractive colour mixing
occurs when mixing together paints that have different pigments
Adding more pigments to a mixture results in ___ wavelengths being reflected (and ___ being absorbed)
Adding more pigments to a mixture results in fewer wavelengths being reflected (and more being absorbed)
Example: why does a mixture of blue and yellow appear green?
Blue reflects mostly short-wavelength (and some medium), absorbs others. Yellow reflects mostly long-wavelength (and some medium), absorbs others. After being combined, both pigments in the paint picture continue to reflect the same wavelengths they did on their own. Only wavelengths that are reflected from a mixture of blue and yellow are medium wavelengths = green
Additive color mixing
occurs when mixing lights of different wavelengths
Example: pure blue light projected on a white board and pure yellow light being projected on a white board create perception of __ because the ___ wavelengths of blue, __ and ___ wavelengths being reflected from yellow combine… so short, medium and long wavelengths are all being reflected causing ___
Example: pure blue light projected on a white board and pure yellow light being projected on a white board create perception of white because the short wavelengths of blue, long and medium wavelengths being reflected from yellow combine so short, medium and long wavelengths are all being reflected causing white
spectral colours
those that appear on the spectrum
non spectral colours
created by mixing spectral colours in various combinations
hue
another term for chromatic colour or what we might refer to as a ‘pure’ color
value
light-to-dark dimension
saturation
determined by the amount of white in a hue
desaturation
more white
HSV (hue/saturation/value) colour solids
can be used to determine additive colour combinations
Trichromatic Theory
states that all human colour vision is based on 3 principle colours (red, green, and blue)
‘normal’ colour vision depends on __ receptor mechanisms i.e. __ types of cones
‘normal’ colour vision depends on 3 receptor mechanisms i.e. 3 types of cones
Physiological evidence for the Trichromatic theory came from measuring the ___ ___ of visual pigments in receptors in 1960s
Physiological evidence for the Trichromatic theory came from measuring the absorption spectra of visual pigments in receptors in 1960s
colour matching experiments show that colours that which are perceptually similar can be caused by different combinations of various physical wavelengths (referred to as ___)
colour matching experiments show that colours that which are perceptually similar can be caused by different combinations of various physical wavelengths (metamers)
cone pigment types differ in the ___ of ___ they absorb from particular parts of the visible light spectrum, it is __ an __ or __ response (i.e. not the case that short ones only respond to blue)
cone pigment types differ in the proportion of light they absorb from particular parts of the visible light spectrum, it is not an all or nothing response (i.e. not the case that short ones only respond to blue)
One receptor type ___ lead to colour vision because any 2 wavelengths can cause the same response in a ___ (someone with only one cone type) simply by altering the ___
One receptor type cannot lead to colour vision because any 2 wavelengths can cause the same response in a monochromat (someone with only one cone type) simply by altering the intensity
principle of univariance
absorption of a photon causes the same effect in all receptors, no matter what the stimulating wavelength is. Once a photon of light is absorbed by a visual pigment molecule, the identity of the light’s wavelength is lost. The only information the neural system encodes/retains is the total amount of light absorbed
Example: if 100 photons of 480nm light is absorbed vs 50 photons for 600 nm light in a monochromat person, the __nm light would look twice as brighter than the __ nm i.e. monochromat person __ ___ between these lights
Example: if 100 photons of 480nm light is absorbed vs 50 photons for 600 nm light in a monochromat person, the 480nm light would look twice as brighter than the 600nm i.e. monochromat person can distinguish between these lights
herings primary colours:
top half= colours with some degree of ___
bottom half= colours with some degree of ___
right half= colours with some degree of ___
left half = colours with some degree of ___
herings primary colours:
top half= colours with some degree of redness
bottom half= colours with some degree of greeness
right half= colours with some degree of yellowness
left half = colours with some degree of blueness
Opponent-processes (3 types)
- White/ Black
- red/green
- yellow/blue
Neural mechanisms respond to white/black, red/green, yellow/blue, in an ___ fashion e.g. by increasing excitation (+) in response to red, and increasing inhibition (-) in response to green
Neural mechanisms respond to white/black, red/green, yellow/blue, in an opposing fashion e.g. by increasing excitation (+) in response to red, and increasing inhibition (-) in response to green
opponent neurons
respond in an excitatory manner to one end of the spectrum and an inhibitory manner to the other, located in the retina and LGN
