Perception & Colour

Question 1

Define perception

Answer 1

The processing of information via the transduction of physical stimuli

Question 2

What are the 8 categories of perception?

Answer 2

• chemoreception (smell/taste)
• mechanoreception (pressure/vibration)
• proprioception (muscle locomotion)
• thermoreception
• equilibrioception (balance)
• photoreception (vision)
• nocioception (pain)
• audition (hearing)

Question 3

What is Rationalism

Answer 3

The idea that prepositions are known to use by intuition alone

Question 4

What is Empiricism

Answer 4

The idea that things are known to us by experience alone

Question 5

What did Democritus believe about vision?

Answer 5

Was an empiricist

• Atoms come to the eyes
• Sight produced by the eyes and the ‘soul’
• Colour is the combination of primary colours (black, red, white and green) but is relative and not absolute

Question 6

What did Plato believe about vision?

Answer 6

Was a rationalist

• Rays come out of your eyes and things interact with those rays
• Colours and vision are so complicated that we cannot predict them

Question 7

What ideas did Alhazen propose about vision

Answer 7

Uses critical evaluation to deduce

• light rays originating from an object travels into your eyes
• white light is composed of many colours

Question 8

What information did Isaac Newton gain from his prism experiments?

Answer 8

• Was believed that prisms added colour to pure light, then tested if putting another prism in front would add more colour
• Instead produced more white light
• colour results from the reflection of wavelengths from objects

Question 9

What did Lomonosov believe?

Answer 9

That the eye contained 3 colour sensitive receptors

Question 10

What idea did Young develop?

Answer 10

The idea of metamers - different physical stimuli that are perceived identically

Question 11

What does the colour of an object depend upon?

Answer 11

The colour it reflects and the colour of the light source

Question 12

What is subtractive colour mixing?

Answer 12

When the colour reflected is the one that is not absorbed (e.g mixing blue and yellow reflect green which they have in common)

Question 13

Give 2 examples of additive colour mixing

Answer 13

1. Lights where blue and yellow produce white light

2. Paints

Question 14

Define the principle of univariance

Answer 14

That a photoreceptor is a function of just one variable

Question 15

What is the Young-Helmholz theory?

Answer 15

That you can match any visible colour with a combination of 3 spectral lights and that there are indefinitely many spectra that give rise to the same colours

Question 16

What is the opponent processing theory?

Answer 16

That the 3 types of cones code for 3 pieces of information about a stimulus

1. black vs white (L + M)
2. blue vs yellow S- (L +M)
3. green vs red (L - M)

Question 17

What is the problem with the opponent processing theory?

Answer 17

That the eye does not have nicely spaced out absorption spectra with L and M especially close, this is inefficient?

Question 18

Why is L and M actually efficient?

Answer 18

The distance between them actually encodes information very effectively

Question 19

What adaptation is seen in neurons?

Answer 19

• Neurons adjust their firing rate to adapt to the average stimulus
• After adapting respond less than they otherwise would have

Question 20

What photoreceptors are usually seen in animals?

Answer 20

2 photoreceptors: L and S (colour and luminance)

Question 21

Which type of colour changes are humans more sensitive for?

Answer 21

More sensitive for luminance than blue/green

Question 22

What is colour blindness caused by?

Answer 22

• Missing or abnormal opsin genes, mostly L & M with rarest type of colourblindness being S
• Gene found on X chromosome so is more common in men that women