1. Mr. Koch AP Psychology Forest Lake High School
The Visual Process
Mr. Koch
AP Psychology
Forest Lake High School

2. The Visual Process Transduction Wavelength Hue Amplitude Intensity
the process by which our sensory systems convert stimulus energy into neural messages
Wavelength
The distance from one wave peak to the next
Hue
The color we experience (determined by wavelength)
Amplitude
Height of the wave peak
Intensity
Amount of energy in light waves, influences brightness (determined by amplitude)

3. Pupil - small opening which allows light to enter.
Fovea (point of central focus)
Retina
Lens
Iris
Cornea
Pupil
Optic Nerve
Lens – focuses the incoming rays by changing its curvature (called accommodation)
Iris – a colored muscle that surrounds and dilates or constricts the pupil (regulates amount of light entering)
Retina – the light-sensitive surface on which the rays focus – the multilayered tissue that lines the inside of the back of the eyeball
Pupil - small opening which allows light to enter.
Blind Spot
*Note: the retina has many receptor cells which convert the inverted image (light energy) into neural impulses. When sent to the brain, these neural impulses are reassembled to create a perceived, upright-seeming image.

5. The Retina Light travels through outer cells to buried receptor cells
called rods and cones.
The rods and cones generate
neural signals to alert the next
layer of cells called the bipolar cells.
The bipolar cells activate the ganglion cells, whose axons converge like strands of rope to form an optic nerve that carries information to the brain.
Where the optic nerve leaves the eye there are no receptor cells, creating a blind spot.
The fovea is where the cones are clustered, the retina’s area of central focus (no rods).

6. Rods vs. Cones Rods Cones
Do not have their own bipolar cells, they share with other rods.
No color.
Remain sensitive in dim light, takes about 20 minutes to adjust
120 million
Periphery of retina
High sensitivity in dim light – help see in the dark.
Many have their own bipolar cells – aids in precise info and detection of fine detail.
Color vision
Do not respond in dim light (can’t see colors in dim light)
6 million
Center of retina
Low sensitivity in dim light

7. Visual Information Processing
Feature Detectors
Certain cortical neurons which receive visual info and respond to only certain features of a scene
Parallel Processing
The brain’s capability to process visual components simultaneously (i.e. a face as opposed to an eye, a nose, etc.) – it breaks vision down into sub-dimensions such as color, depth, movement, and form

8. Color Vision Young-Hemholz Trichromatic Theory
We can discriminate 7 million different shades!
1 in 50 people are “color-deficient”
(esp. males – genetic)
Young-Hemholz Trichromatic Theory
The retina has 3 types of color receptors – each sensitive to red, green, or blue. When we combine these, we get all the other colors
Herring: afterimages – Opponent Process Theory
After leaving the receptor cells, visual information is analyzed in terms of opponent colors
Red/Green; Blue/Yellow; Black/White
White contains all colors in spectrum

9. Color Vision Summary Color Constancy
The retina’s red, green, and blue cones respond in varying degrees to different stimuli; their signals are then processed by the nervous system’s opponent-process cells en route from the thalamus to the visual cortex
Color Constancy
Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the objects
Perception of color is influenced by the context