colour vision

Question 1

Wavelength

Answer 1

Varies smoothly and evenly but our perception of colour doesn’t

Question 2

Colour mixing

Answer 2

Most light we see from the sun is white
When we mix types of light together we see different colours

Question 3

Colour addition

Answer 3

Any single wavelength can be perfectly matched by a mixture of three other wavelengths
Trichromacy theory

Question 4

Rod receptors

Answer 4

Rods only useful when not a light of around
Help us in low light conditions like climbing up the stairs when the light is off

Question 5

Red cone

Answer 5

Long wavelength cone
564nm
Get a lot of them

Question 6

Green cone

Answer 6

Medium wavelength cone
534nm
Get a lot of them

Question 7

Blue cone

Answer 7

Short wavelength cone
420nm
Don’t get many of them

Question 8

Colour perception

Answer 8

Each type of cone responds to a range of wavelengths but has peak sensitivity at their set nm

Question 9

Colour matching experiements

Answer 9

Trichromacy theory supported because we can make any colour by adjusting intensity of three colours of light
RGB - like stardew

Question 10

Principle of univariance

Answer 10

If we only operate with rods, it can’t detect changes in intensity and wavelength
No way of telling if the change is in intensity or wavelength
Human suffer the changes in univariance at night
Brain detects changes in brightness, no changes in colour

Question 11

Two receptor system

Answer 11

Each stimulus activates both receptors in different ratios
Ratio doesn’t change changes in intensity
Colour can be calculated by looking at the ratio of activity in the two channels

Question 12

How to calculate colour in two receptor system

Answer 12

Take output of each cone to look at colour and total amount for brightness
Two types of cones are necessary to perceive wavelengths, with only one cone it only detects variations in brightness
If one medium wavelength cone is used it will be stimulated the same by a high intensity red light or a low intensity blue light

Question 13

Primordial system

Answer 13

Most mammals are dichromatic with few short wavelength cones and lots of medium cones
Blue/yellow system
Little spatial resolution

Question 14

Second subsystem

Answer 14

Long wavelength cones split into two to make a red/green system
Old world primates
Evolved with certain fruits so we could forage them

Question 15

Monochromats

Answer 15

Only have one cone type or just rods

Question 16

Dichromats - Protanopes

Answer 16

Lack long wavelength cone (red)

Question 17

Dichromats - Deutranopes

Answer 17

Lack middle wavelength cone (green)

Question 18

Dichromats - Tritanopes

Answer 18

Lack short wavelength cone (blue)

Question 19

Anomalous trichromats - Protanomaly

Answer 19

Abnormal long wavelength cone

Question 20

Anomalous trichromats - Deuteranomaly

Answer 20

Abnormal medium wavelength cone

Question 21

Opponent processes

Answer 21

Two subsystems of colour vision

Question 22

How opponent processes work

Answer 22

Process of excitatory and inhibitory responses, with the two components of each mechanism opposing each other
Red creates positive response in a cell, green creates inhibitory response
When this cell is activated it tells the brain that you are seeing red

Question 23

What does antagonistic interaction help with

Answer 23

Help visual system detect colour contrasts and edges more effectively

Question 24

Comparison of short with long/medium (blue/yellow)

Answer 24

Not spatially antagonistic
Does not have the excitatory and inhibitory responses of red/green
Old shared with other mammals
Own ganglion cells to koniocellular layers of LGN and then layers 2-3 of V1

Question 25

Comparison of medium with long (red/green)

Answer 25

Spatially antagonistic
New to old world primates
To parvocellular layers of LGN
Layer 4ca of V1
Piggybacked on the existing colour system

Question 26

Colour constancy

Answer 26

Our ability to work out colours despite large changes in wavelength of the lighting
Colour of the dress changes depending on what our brain thinks the illumination is

Question 27

Colour aftereffect and opponent processes

Answer 27

When staring at an image for too long, the relevant cells in the opponent cells (red and white) will be fatigued and start sending weaker signals to save energy
When you shift our focus the cells no longer have the stimuli telling them to fire, so the white and red receptor cells will de-activate, leaving our black and green cells to activate in response
If you stare at the inverted Welsh flag for too long, then move away, it will look normal because of the opposing cells firing