PSYCH 2220 Perception Lecture 9 COLOUR Trichromacy cones

PSYCH 2220 Perception Lecture 9

COLOUR Trichromacy cones, three photopigments, long wavelength, medium wavelength, short wavelength, colour matching, 'normal' need three lights, colour blindness Opponency adaptation, colour after-effect, lateral inhibition (at level of retinal ganglion cells)

VISUAL ILLUSIONS A classification system: 1 Adaptation illusions 2 Simulation illusions 3 Incompatible cue illusions 4 Geometric illusions

VISUAL ILLUSIONS A classification system: 1 Adaptation illusions 2 Simulation illusions 3 Incompatible cue illusions 4 Geometric illusions

VISUAL ILLUSIONS A classification system: 1 Adaptation illusions 2 Simulation illusions 3 Incompatible cue illusions 4 Geometric illusions

VISUAL ILLUSIONS A classification system: 1 Adaptation illusions 2 Simulation illusions 3 Incompatible cue illusions 4 Geometric illusions

Müller-Lyer Illusion

BOTTOM UP…. TOP DOWN ….

BOTTOM UP 1 eye movements 2 limited acuity 3 physiological confusion

response level cells in a hypercolumn minding their own business

response level when a bar comes on they give a response…

response level But the cells are wired together with INHIBITORY connections

response level so highly active cells inhibit their neighbours the most

response level which releases the higher-firing cells from inhibition and makes them fire more, bringing out the signal better

response level Now we add some other lines. .

response level Which activate the cells tuned to those orientations…

response level Which pulls down the response of the vertically tuned cell

A physiological confusion explanation for the Müller-Lyer

BOTTOM UP 1 eye movements 2 limited acuity 3 physiological confusion TOP DOWN 1 empathy 2 “good figure” 3 perspective

small thing close big thing far EMMERT’s LAW If retinal image stays the same then perceived size will depend on distance

The Thatcher Illusion

Do we need to LEARN to see?

EMPIRICIST (all knowledge comes from experience) NATIVIST (knowledge is ‘a priori’; you are born with it)

EVIDENCE 1 Animal behaviour 2 Blind people recovering their sight 3 Babies’ visual development 4 Adaptation experiments 5 Controlled rearing experiments

1 animal behaviour

Molyneux’s question: “could a man born blind distinguish a sphere and a cube by sight alone? ” 2 blind people recovering sight

3 child development, Fant’z Experiment

4 adaptation

4 adaptation

5 controlled rearing

Blakemore video about development

EVIDENCE Animal behavour …………. Nativist Blind people recovering their sight… Empiricist & nativist Babies’ visual development …………. Empiricist & nativist Adaptation experiments …………… Empiricist Controlled rearing experiments ………. . Empiricist