Week 2- High level Vision Flashcards
Colour vision depends on how many types of cones
3
Colour information is encoded in the retina by
- Midget cells (signalling red-teal differences).
- Small bistratified ganglion cells (signalling lime-violet differences)
The genes encoding the Medium and Long photosensitive pigments lie on
The X chromosome
Normal trichomats have one copy of
The L photopigment gene followed by one or more copies of the M photopigment gene
In dichromacy either the M or the L photopigment gene is
- Missing
- This means the retina only contains 2 types of cone
For dichromats colours vary along
One dimension only
In anomalous trichromacy, one photopigment gene is
- Hybrid
- Contains sections of M and L photopigment genes
In anomalous trichromacy, red-teal signal carried by the midget cells is
- Weaker.
- Because the two cone types provide similar info.
- Red teal colour differences is muted
Colour vision depends on
- Bottom up signals
- Higher level perceptual processes
The visual system maintains
- Colour constancy
- Object perceived as stable despite changes in the colour of the illumination
The light reflected from objects depends on
- The object’s reflectance spectrum
- The illumination spectrum
The spectrum of light that falls on the retina is a product of
- The illumination spectrum
- The reflection spectrum
The visual system must discover the spectrum of the illuminant to
- Discount it
- This is so that perception can represent the object’s stable reflectance spectrum
The ratio law can partly account for
Lightness constancy
What’s the Gleb effect
Perceived lightness can flip from white to black once the true luminance of the illumination is known
Why don’t objects typically seem smaller when further away
The visual system maintains size constancy
Emmert’s law
Perceived size is proportional to the product of retinal image size and perceived distance
Bayesian inference
The idea that seeing the expected can be brought into the mathematical framework of Bayes’ theorem
Perception depends on both
- ‘bottom up’ signals from the sense organs
- ‘top down’ signals from the brain carrying expectation and context
