L9 - Visual Appearances

Question 1

What does it mean to perceive?

Answer 1

• Link to the world, inner & outer
• Provides a sense of what’s real & what ‘exists’
• Links what we experience to how it maps to reality
• All animals that exist have a sensory system

Question 2

What is the concept of “Unwelt”?

Answer 2

Umwelt - self-centred world - unique for each animal

• Different animals have very different experiences of what the world is like, both in space and in time
  
  • e.g. Bird have 4 cone types
  • e.g. Snakes can sense IR light so can follow warm-blooded animals
• Need to understand an animals experiences about the world to understand it’s behaviours & understand behavioural tasks
• Different species have developed different adaptations that require different kinds of information = Different types of intelligence?

Question 3

What are the two functional roles for vision?

Answer 3

1. Control of behaviour/action
2. Recognition and awareness of the ‘world’ (visual experience)

Question 4

What is the problem of visual experience?

Answer 4

• Brains have to try and figure out what’s in the world from the light that reaches our eyes
• But images are 2D & a lot of different factors that affect the structure in the images are mixed together

Question 4

What is light?

Answer 4

• Light is a form of radiation
• Vision involves using the patterns in light (spatio-temporal structure) to extract properties of the world
• The structure in the light that conveys information about the properties of the world = Ecological optics

Question 5

What are the different ‘levels’ of visual processing

Answer 5

• ****Low-level -**** Involves the encoding and transduction of image: their spatial, chromatic and temporal structure - only the encoding of the retinal image (brain wants to know what caused the image in the world)
• ****Mid-level**** - First stage where properties of environment are made explicit: the shapes, material properties, and coherence of substances and surfaces in the world (not just images only)
• **High-level** - The semantic interpretations of sense, such as object recognition, categorization or classification

Question 6

How does light interact with objects?

Answer 6

• Light interacts with objects and materials
  
  • These interactions generate the structure in images - Need to understand what they convey about the world
  • There are a number of physically independent sources of light-material interactions that was seem to be sensitive to (shape, colour, lightness, gloss (‘shiny-ness’), texture, and opacity/translucency).

Question 6

What are the different factors create the structure in light that reaches our eyes?

Answer 6

Three-dimensional shape (change in surface pose relative to the light source)
- Reflectance and transmittance properties (colour, lightness, translucency, gloss) - How light bounces off an object
- Colour & lightness
- In order to extract the lightness or colour of an object in the world, you need to know what the light source is like (its wavelength composition and intensity)
- Colour isn’t just about sensing the wavelengths of light that are in the image
- Transparency
- Translucency and sub-surface scattering
- Sub-surface scattering - light bounces around within an object
- Gloss
- Illumination (intensity, spectral content, shadows)
- Shadows
- Blueish tinge of shadows caused by warmer light nearby
- Occlusion
- Partial occlusion - Problem of completion (amodal completion)

    - Border ownership - Not the animal ending but the object in front
    - Cephalopods are masters at camouflage
- Optics of the eye