Lecture 10 Flashcards
Inverted Spectrum
The hypothetical concept, pertaining to the philosophy of colour, of two people sharing their colour vocabulary and discriminations, although the colours one see’s one’s qualia - are systematically different from the colours the other person sees
Qualia
The subjective, first-person experiences of perception and sensation that are inherently personal and difficult to communicate or measure objectively. They represent the ‘‘what it is like’’ aspect of experiencing the world
-E.g. the redness of red, the pain of a headache, the sound of a violin
Mary’s Room Thought Experiment
If Mary learns something new when she experiences colour for the first time, this implies that there is more to knowing about colour than just the physical facts
-Against Physicalism
-In favour of Dualism or Non-Physicalist Views
The Principle of Univariance
An infinite set of different wavelength x intensity combinations can elicit exactly th same response from a single type of photoreceptors. Therefor, one type of of photoreceptor cannot make colour discriminations based on wavelength
Trichromacy
-Colour perception cannot be determined by a single photoreceptor type alone
-With 3 cone types, we can tell the difference between lights of different wavelengths
-For every wavelength, there is a particular combination of activity across the 3 type of cones
every frequence above S-cone limit is only encoded by L-cones and can therefor produce the same responses for different wavelength/intensity combination
Imagine you don’t have M-cones…
can’t distinguish between green/red
Without M-cones..
Colour-Anomalous
A term for what is usually called ‘‘colour blindness’’. Most ‘‘colour-blind’’ individuals can still make discriminations based on wavelength. Those discriminations are just different from the norm
Deuteranope
Due to absence of M-cones
Protanope
Due to absence of L-cones
-See blue/yellow
Tritanope
Due to absence of S-cones
-See red
Cone Monochromat
Has only one cone type; truly colour-blind
Trichromacy
The theory that the colour of any light is defined in our visual system by the relationships of 3 numbers, the outputs of 3 receptor types now known to be the three cones
Metamers
Different mixtures of wavelengths that look identical; more generally, any pair of stimuli that are perceived as identical in spite of physical differences
-Different patterns of wavelength can cause the same activity
Additive Colour Mixing
The process of creating colours by combining different wavelengths of light. The primary colours in this mixing are red, green, and blue (RGB). When all 3 are combined at full intensity, they produce white light. This is the basis for colour displays like TV screens and computer monitors
Subtractive Colour Mixing
The process of creating colours by removing (absorbing) certain wavelengths of light. The primary colours in this mixing are cyan, magenta, and yellow (CMV). When combined, they absorb more light and produce darker colours, with all 3 mixing to form black. This is used in printing, painting, and pigments.
Nonspectral Hues
Hues that can arise only from mixtures of wavelength, i.e. there is no ‘‘purple’’ in the spectrum, it has to come from a particular combination of activity across S, M and L cones
-You can see them, but not in the spectrum of light
Ewald Hering’s Opponent Colours Theory
Some colour combinations are percieved as ‘‘legal’’, while others are ‘‘illegal’’
-This supports the opponent-process theory, where colours are processed in opposing pairs :
Red vs. Green
Blue vs. Yellow
Legal Colours
-Bluish-green
-Reddish-yellow
-Bluish-red
Illegal Colours
-Reddish-green
-Bluish-yellow
(Opposite on colour wheel)
Hue Cancellation Experiments
A method used to determine opponent colour processing. Participants adjust the amount of an ‘‘opponent’’ colour (e.g. adding green to cancel out red) until no trace of the original hue remains. This helps map the sensitivity of the visual system to different colour opponencies (red-green, blue-yellow)
