Wednesday 10/28 Quiz 25: Color Vision and Gestalt (p178-183)

Trichromatic Theory

ONE OF THE TWO MAJOR THEORIES OF HOW WE SEE COLOR

Hypothesizes that we have three types of cones in the retina: cones that detect the primary colors of light - blue, red, and green

These cones are activated in different combinations to produce all of the colors of the visible spectrum

This theory explains how we see color BUT IT CANNOT explain such visual phenomenon as afterimages and color blindness

Opponent Process Theory of Color Vision

THE OTHER MAJOR THEORY OF HOW WE SEE COLOR

We see colors as OPPOSITE PAIRS of color. Ganglion cells in the retina come in pairs: red/green pairs, yellow/blue pairs, and black/white pairs

Memory trick for the color pairs: Christmas, Blue Cheese, Chessboard

If one color sensor is stimulated, its opposite color pair is inhibited from firing.

THIS explains after images and color blindness

Color Blindness

This usually means you have trouble distinguishing reds and greens. Usually, this does not mean that the person can't see any color. It is usually only one of the pairs of colors in the opponent process theory - a weakness with the pair red and green is the most common form of this.

1 out of 10 men have some form of this, and it is not frequently found in women

Common form- Individuals with dichromatism color blindness cannot see either red/green shades or blue/yellow shades

Rare form- Those who have monochromatism color blindness see only shades of gray

Afterimages

Part of the Opponent Process Theory for Color

If one sensor is stimulated, its pair is inhibited from firing.

If you stare at the green part of this flag, you will tire out the green part of the pair. When you look away, the opposite part of the pair, red, will be wide awake so you will see a red afterimage.

Gestalt

Based on the observation that we normally perceive images as groups, not as isolated elements

This process is believed to be innate and inevitable

"The whole is greater than the sum of its parts"

Figure and ground

GESTALT RULE on how we focus on an object in our visual field

the organization of the visual field into objects that stand out from their surroundings - when you look at one thing (a figure), everything else fades to the background (the ground)

reversible figure and ground

In some optical illusions, a figure-ground pattern might reverse as it is viewed -- the figure becomes the ground and the ground becomes the figure.

In the attached picture if you see the VASE the FACES become the background. But when you see the FACES the VASE becomes the background.

Similarity

GESTALT RULE when we perceive objects that are alike are grouped together

Closure

GESTALT RULE on how our brain just fills in the gaps to create a complete, whole object.

This picture: we assume that the circles on the right are complete but partially blocked by the (illusory) triangle or our brains complete the panda

Proximity

GESTALT RULE on how we group objects that are close to one another.

We group nearby figures together. In this picture, the group on the right is much closer to each other, so we group them together.

apparent motion

two individual shapes may be perceived as a moving object if they are presented one after the other within a short time span - OUR BRAIN IS CREATING MOVEMENT WHEN NONE IS ACTUALLY THERE