Perception L2: Seeing I

Refraction

Refraction

Bending of light, light refracted by cornea and lens to focus image on retina

Myopia

Near-sightedness, image focused in front of retina, eye too long, can be corrected by concave lens

Hyperopia

Far-sightedness, image focused behind retina, eye too short, corrected by convex lens

Accommodation

Constant adjustment of the lens by ciliary muscles to allow us to focus near and far

Isomerization

Millions of visual pigment molecules in the outer segment of rods and cones, changes shape when absorbing light leading to chemical chain reaction that activates receptor

Rods

Black and white, very sensitive, not detailed, 91 million, high density in retina, none in fovea

Cones

Color, less sensitive, sharp vision, 4.5 million, high density in fovea

Neural Convergence

One ganglion cell can receive 120 times more signal from rods than from cones

Acuity

When we want to spot details we focus images on our fovea, neural convergence of rods can result in less detailed information

Primary Visual Cortex (Striate Cortex)

Primary receiving area for vision, basic information about light, lines, location, and orientation is processed

Dorsal Pathway

Goes up, processes where (location) information and how (how to interact with) information

Ventral Pathway

Goes down, processes what (identity, recognition) information

Apparent Motion

Two separate shapes are perceived as one moving object when presented one after another within a short timespan, Max Wertheimer

Visual Object Agnosia

Inability to recognize familiar objects via visual modality

Apperceptive Agnosia

Failure to recognize objects, to discriminate, objects, shapes, and basic forms

Associative Agnosia

Failure to link perception with stored knowledge, problem is in linking perception to sotred representation

Prosopagnosia

Difficulty recognizing familiar faces

Similarity

Elements that are similar are grouped together

Proximity

Elements that are close together in space or time are grouped together

Good Continuation

Elements that follow the same direction are grouped together

Closure

Elements that are part of a closed figure are grouped together

Common Fate

Elements moving in the same direction and speed are grouped together