Perception Flashcards
Lens
Focuses light as it enters the eye
Retina
Contains photoreceptors (rods and cones) which transduce light into electrical signals (action potentials)
Fovea
The centre of the retina which contains the highest density of cone receptors. Supplies the brain with fine-
grained details and colour
Visual pathway
Visual information travels from eyes to Lateral Geniculate Nucleus (LGN) -> Calcarine sulcus in V1 -> Feature detectors -> hierarchical processing from V1 to the temporal and parietal lobes could bind line features into complex shapes
Contralateral mapping
Light coming from the left side of space (left visual field) is sent to the right hemisphere (left visual cortex) and vice versa
What makes visual perception hard? Solution?
- Objection constancy
- Inverse projection problem
Solution: Unconscious Inference
Object constancy
The very same object can project a different image on your retina because of:
- Viewing angle
- Lighting
- Distance
- Partial occlusion
Inverse projection problem
Each 2D retinal image could reflect infinitely many distinct 3D stimuli
Likelihood principle
We perceive the object that is most likely to have
caused the pattern of stimuli that we received
- Views perception as a form of problem
solving
- We unconsciously and automatically draw
inferences that are based on experience and
basic principles of simplicity
What does the likelihood principle allow?
Top-down biases on perception (top-down processing = Processing that involves a person’s knowledge or expectations)
Bayesian Inference Models
The idea that our estimate of the probability of an outcome is determined by the prior probability (our initial belief) and the likelihood (the extent to which the available evidence is consistent with the outcome).*
Gestalt psychology
Involves heuristics (a “rule of thumb” that provides a best-guess solution to a problem) used by the visual system in order to perform figure ground segregation (identifying a figure from a background)
Gestalt principles
- Similarity
- Closure
- Proximity
- Good continuation
- Good figure/simplicity
Similarity
Points which share features are grouped together
Closure
Points form closed (whole) objects
Proximity
Points close in space are grouped together
Good continuation
Points are assumed to be connected by smooth lines