WK3

• What are the two main questions concerning Trichromacy Theory?


  Is the theory complete? Is the theory correct?
• What does it mean for Trichromacy Theory to be complete?


  It means it explains all the facts concerning colour perception.
• What does it mean for Trichromacy Theory to be correct?


  It means it accurately explains the facts and fits with all the facts.
• What happens when you add coloured lights together according to Trichromacy Theory?


  • The outcome resembles both of the two components of the mixture.
  • For certain mixes, a different outcome occurs.
• What are the four special colours mentioned in the study material?


  Reddish yellow, yellowish green, greenish blue, reddish blue.
• What is the significance of the four special colours in relation to Trichromacy Theory?


  They form pairs that cancel one another out when added together.
• What was the reaction of one individual to the omission in Trichromacy Theory?


  He proposed a theory of colour vision very different from Trichromacy Theory.
• What is the name of the theory proposed as an alternative to Trichromacy Theory?


  Opponent colours theory.
• How many types of receptors does the Opponent colours theory propose?


  Four types of receptor/detector.
• How are the receptors organized in the Opponent colours theory?


  They are organized in opposing pairs.
• What are the three types of detectors in Trichromacy theory?


  Red light detector, green light detector, blue light detector.
• How is perceived colour determined in both Trichromacy and Opponency theories?


  By the pattern of responses from the detectors.
• Why was the Opponent colours theory initially doubted?


  Because it contradicted the established three types of receptors proposed by Young and Helmholtz.
• What discovery about opponent mechanisms was made around the same time as the confirmation of three types of receptors?


  Opponent mechanisms were discovered in primates and later confirmed in humans.
• What is the significance of the ganglion cell layer in the retina?


  It has far fewer cells than the other two layers.
• How do ganglion cells connect to photoreceptors?


  They connect via horizontal and bipolar cells.
• What are the two basic types of ganglion cells mentioned?


  Those connected to all types of cones and those connected to L- and M-cones only.
• What is the function of L - M cells?


  They are excited by signals from L-cones and inhibited by signals from M-cones.
• What is the function of M - L cells?


  They are excited by signals from M-cones and inhibited by signals from L-cones.
• What do S - (L+M) cells do?

  They are excited by signals from S-cones and inhibited by signals from M- and L-cones.
• What do (L+M) - S cells do?

  They are excited by signals from M- and L-cones and inhibited by signals from S-cones.
• How does adding red and green primaries produce yellow?


  Red and green cancel one another out in the r-g opponent mechanism, exciting the yellow detector part of the b-y mechanisms.
• What is the limitation of ganglion cells in relation to opponent units?


  Ganglion cells cannot 'fire' below zero.
• What does the modified trichromacy theory state about photoreceptors?


  Three different types of photoreceptor contribute to colour vision.
• What is the average distribution of cones in a colour normal human retina?

  55% L-cones, 35% M-cones, and 10% S-cones.
• What does the distribution of cones in the foveola indicate?


  1. cones are absent from the foveola and increase in number as you move outward across the macula.
• What is the implication of the distribution of cones for trichromacy theory?


  It is not compatible with any version of trichromacy theory, which predicts blue blindness in central vision.
• What is Colour Constancy?


  The perceived colour of a visible surface remains the same when the spectrum of the light illuminating the surface changes.
• Why does trichromacy theory predict that colours should change with changes in illumination?


  Because changes in illumination affect the wavelengths of light reaching the eyes from reflecting surfaces.
• What is the relationship between proximal stimulation and perceived properties like colour, size, and shape?


  A perceived property remains the same when the proximal stimulation changes.
• What are the examples of perceptual constancies mentioned?

  • Colour Constancy
  • Size Constancy
  • Shape Constancy
• What is the definition of reflectance?


  Reflectance is the proportion of light of particular wavelengths that a surface reflects back when illuminated.
• How does cooking affect the reflectance of a surface?


  Cooking changes the chemical composition of the surface, altering its reflectance.
• What is the spectral reflectance function?


  It is a graph showing the proportion of incident light of a particular wavelength that a surface reflects.
• Why is it important to distinguish between reflectance and light?


  Reflectance is a permanent property of a surface, while light is variable and depends on the illumination conditions.
• What is the relationship between surface properties and perceived colour?


  • Surface properties determine how much light is reflected.
  • Different materials have different reflectance functions.
  • Perceived colour corresponds to the physical properties of the surface.
• What is the main topic discussed in the section titled "The distal stimulus in surface colour perception"?


  The relationship between surface materials and their reflectance functions in color perception
• How does cooking a patty affect its surface in terms of color perception?


  Cooking changes the chemical composition of the surface, altering its reflectance
• What does it mean when we say surfaces with different reflectance functions appear to have different colors?


  It means that the way surfaces reflect light at different wavelengths influences our perception of their color
• What is reflectance?


  Reflectance is the proportion of light of particular wavelengths that a surface reflects