PSYC 323 - Lecture 19

Why is the eye not like a camera?

Vision relies heavily on brain interpretation (top-down processing), not just recording images.

What is bottom-up processing in vision?

Raw sensory signals travelling from the eye to the brain.

What is top-down processing in vision?

The brain using expectations and context to interpret sensory input quickly.

Why is top-down processing important for survival?

Bottom-up processing alone would be too slow to recognise objects in real time.

Why is vision called a “far sense”?

Because light travels very fast, allowing detection of distant objects.

What is the inverse optics problem?

The brain must infer object properties from reflected light, not directly from objects.

What does the amount of reflected light mainly influence?

Perceived lightness/brightness.

What does the pattern of reflected light mainly influence?

Perception of shape and texture.

What is a photon?

fundamental, elementary particles that make up light

How does wavelength relate to photon energy?

Shorter wavelength = higher energy; longer wavelength = lower energy.

What is the visible spectrum range for humans?

About 380–750 nm.

Name 4 ways light interacts with matter.

Absorption, reflection, diffraction, refraction.

what is absorption?

the process where matter takes in light energy rather than reflecting it or letting it pass through

what is diffraction?

the bending and spreading of light as they bend around obstacles

what is reflection?

light bounces off an object

What is refraction?

chanced in direction of light when passing from one medium to another

What structures focus light onto the retina?

Cornea and lens (with pupil/iris controlling light entry).

What is the role of the pupil?

Controls how much light enters the eye by dilating or constricting.

What factors influence pupil size?

Light level, autonomic activity (emotion), drugs, and age.

What is lens accommodation?

The lens changing shape to focus on near vs far objects.

What are cataracts?

Lens opacification (clouding) of the eye's natural lens, usually caused by aging, due to the breakdown of structural proteins in the lens which blurs vision

What is myopia vs hyperopia?

Myopia = near-sighted (focus in front of retina); hyperopia = far-sighted (focus behind retina).

What are rods and cones specialised for?

Rods = low-light, low acuity; cones = bright light, colour, high acuity.