Ch 4 Vision

TransductionConversion of one form of energy to another.

How is this important when studying sensation?

Stimulus energies to neural impulses.

For example:

Light energy to vision.

Chemical energy to smell and taste.

Sound waves to sound.

We only use light energy to see.

What makes up a light wave?

Wavelength

The distance from the peak of one light wave to the peak of the next.

The distance determines the hue (color) of the light we perceive.

The amount of energy in a light wave.

Determined by the height of the wave.

The higher the wave the more intense the light is.

Structure of the Eye

Nearsighted Vision

Farsighted Vision

The Retina

SaturationIf the human eye was not responsive to

differences in the purity of light waves we would not be able to perceive differences in Saturation.

Feature DetectionCells in the visual cortex that respond selectively to specific features of complex stimuli. Examples include: shape, angle or movement.

Parallel Processing

The processing of several aspects of a problem simultaneously.

Color Motion Form Depth

How do we see in color?

What color are the Eagles wearing?

• The Eagle Uniform is anything but red.

• The uniform rejects the long wavelengths of light that to us are red.

• So red is reflected off and we see it.

• Also, light has no real color.

• It is our mind that perceives the color.

2 major color theories

Young-Helmholtz Trichromatic (3 color) Theory

Any color can be created by combining the light waves of three primary colors

3 different types of receptor cells in our eyes. Together they can pick any combination of our 7 million color variations.

Most colorblind people simply lack cone receptor cells for one or more of these primary colors.

Principle of Additive Color Mixing

At “Showtime” you may notice that whenever the red and green spotlights overlapped, they seemed to change to a yellow spotlight.

Opponent-Process TheoryWe cannot see certain colors together in

combination. These are antagonist/opponent colors.

white-blackgreen-red

yellow-blue

O

opposite opponent colors are never perceived together – there is no "greenish red" or "yellowish blue"