2: Perception

Question 1

Perceptual illusions

Answer 1

Perceptual errors- Muller-Lyer illusion; necker cube; Kaniza’s 1976 illusory.
If perception was simple, illusions wouldn’t occur.

Question 2

What is perception?

Answer 2

Receiving information from the environment using sensory organs (eyes, ears, nose, mouth, touch).
Sensory input is sent to the brain.

Definitions- Sensation is the ability to detect various forms of energy without making sense of it.
Perception is the process that analyses and makes sense of sensory input.

Question 3

Biology of the eye

Answer 3

Environment to the retina:
Incoming light passes through cornea into anterior chamber.
Passes through the lens into major chamber (filled with vitreous humour).
Light is focused upside down into the retina, by the lens/cornea combination.

Retina to the optic nerve:
Cones- used for colour vision.
Rods- used to detect dim light and movement.
Information is passed to ganglion cells (axons of ganglion cells form optic nerve).
Carry;s electrical signals to visual cortex (in the brain).

Visual cortex to visual pathways: Information transmitted down two independent pathways.
Ventral pathway- processing colour and form.
Dorsal pathway- processing movement and spatial relations.

Question 4

Gibson’s theory of direct perception (1979)

Answer 4

Bottom up- perception directly from the environmental input.
Action driven- Purpose is to enable interactions with the real world.

Theory is ecological- didn’t agree with lab investigations.

Ambient optic array- structure imposed on light waves reflected by textured surfaces.
Light reflections converge at the point occupied by the observer.
As you move, your head is altered with respect to the environment; optic array changes accordingly.

Invariants- Features of the environment that provide unambiguous information; don’t change as we move (eg. the horizon).

Optic flow- describes changes in light from the ambient optic array; results from motion.
Flow patterns give information about what’s going on in the environment.
When travelling forward, the heading point is “the pole”.
Rules: if there is flow the observer is in motion; outflow from the pole specifies approach; change in pole direction means observer has changed direction.

Question 5

Evidence for Gibson’s theory: Bruggeman, Zosh & Warren (2007)

Answer 5

Tested importance of optic flow patterns.
Put participants in virtual reality- had to walk through environment with heading displaced 10 degrees from direction; environment either provided rich optic flow or none.
Performance was better with access to optic flow information.

Question 6

Gibson’s theory: Affordances

Answer 6

Argued the potential use (affordance) of objects is directly perceivable without relying on stored knowledge- no need for top down processing.

Evidence:
Pappas & Mack- presented images briefly so top down processing couldn’t be engaged. Objects main affordance produced motor response; provides evidence that potential use is directly perceived without top down processing.

Question 7

Limitations to Gibson’s view

Answer 7

• Correctly identified information can be gained directly from the environment via the optic array; but doesn’t specify how it’s picked up.
• Ignored role of stored knowledge in processing.
• Saw no place for top down processing (including memory); oversimplification.