Lecture 13 Flashcards
V4 was originally proposed as a sort of ‘___ __’
V4 was originally proposed as a sort of ‘color centre’
Achromatopsia
color blindness, can cooccur with prosopagnosia
Monochromats
has a very rare hereditary condition which could be considered to produce ‘true’ colour-blindness
Monochromats have no functioning ___ (only ___), leading them to only perceive the world in tones of white, grey and black
Monochromats have no functioning cones (only rods), leading them to only perceive the world in tones of white, grey and black
Monochromats have __ visual acuity because of lack of ___
Monochromats have poor visual acuity because of lack of cones
Monochromats are __ sensitive because of having all ___
Monochromats are very sensitive because of having all rods
Dichromats
are missing one of the 3 types of cones
3 types of dichromats
protanopia, deuteranopia and tritanopia
unilateral dichromats
has trichromatic vision in one eye and dichromatic in the other
Protanopia
missing the long-wavelength pigment, see short-wavelengths as blue, a form of red-green colourblindness (red looks more green and less bright ), above neutral point of 492 nm they see yellow
Deuteranopia
missing the medium-wavelength pigment, see short-wavelengths as blue, a form of red-green colourblindness (green look more red), above neutral point of 498nm they see yellow
Tritanopia
missing the short-wavelength pigment, see short-wavelengths as blue, a form of blue-yellow colour-blindness (difficulty separating blue and green, red and yellow), above neutral point of 570 nm they see red
Colour constancy
perception of colours as relatively constant in spite of changing light sources
Chromatic adaptation
occurs with prolonged exposure to chromatic colours. When the stimulus colour selectively bleaches a specific cone pigment over an extended period of time, this results in a decrease in sensitivity to the associated color
Colour constancy works best when an object is surrounded by ___ ___
Colour constancy works best when an object is surrounded by many colours
Showing participants scenes with masked surrounding ___ ‘accuracy’ of colour perception reports
Showing participants scenes with masked surrounding reduces ‘accuracy’ of colour perception reports
Hansen et al. showed participants photographs of fruits e.g. strawberries with characteristic colours against a grey background. When shown a spot of light which physically matched the grey background, participants accurately perceived the spot as being grey. However, when the fruits were adjusted to be grey, they were still perceived as being slightly coloured in a characteristic way i.e. participants reported seeing a grey strawberry as being slightly reddish
This was interpreted to mean that …
past knowledge of an object’s colour impacts colour perception
Lightness constancy
achromatic colours are perceived as remaining relatively constant across different lighting condition
Lightness
perception of the shade of achromatic colour (white, grey, black)
Perception of lightness is not related to the __ ___ of light reflected by an object, but rather the __
Perception of lightness is not related to the total amount of light reflected by an object, but rather the percentage
The intensity of light reaching the eye from an object depends on:
1) the intensity of illumination (total amount of light hitting the object)
2) The object’s ____ (the proportion of light reflected back by the object)
The intensity of light reaching the eye from an object depends on:
1) the intensity of illumination (total amount of light hitting the object)
2) The object’s reflectance (the proportion of light reflected back by the object)
Lightness constancy is determined by ___ not __
Lightness constancy is determined by reflectance not intensity
Ratio principle
states that two areas reflecting different amount of light look the same if the ratios of their intensities are the same
When perceiving lightness under uneven illumination, the perceptual system must distinguish between…
reflectance edges and illumination edges
Reflectance edges
edges where the amount of light reflected changes between two surfaces i.e. changes in material
Illumination edges
edges where lighting of two surfaces changes i.e. changes in lighting
Bornstein et al. found by the ___ ___ technique and the pattern of __ and ___ to 3 wavelengths, that ___ __ have colour vision
Bornstein et al. found by the looking time technique and the pattern of habituation and dishabituation to 3 wavelengths, that young infants have colour vision
