Ch. 5.1. Visual Coding Flashcards
What was Ibn al-Haytham’s evidence that we see only because
light enters the eyes, not by sending out sight rays?
- you can see distant objects such as stars far faster than we could imagine any sight rays reaching them.
- when light strikes an object, we
see only the light rays that reflect off the
object and into the eyes
According to the law________ , if you electrically stimulate the auditory receptors in your ear, what would you perceive?
the law of specific nerve energies
Because of the law of specific nerve energies, you would perceive it as sound, not as shock.
(Of course, a strong enough shock might spread far enough to excite pain receptors also.)
What makes the blind spot of the retina blind?
It has no receptors because it is occupied by exiting axons and blood vessels.
If you found a species with a high ratio of cones to rods in its retina, what would you predict about its way of life?
We should expect this species to be highly active during the day and seldom active at night.
According to the trichromatic theory, what causes you to perceive red?
A perception of red occurs only if the long-wavelength cone has a high ratio of response relative to the other two types of cone.
Activity of the long-wavelength cone is not sufficient.
In fact, notice that the long-wavelength cone responds
to what we call yellow more than to what we call red.
According to the opponent-process theory, under what cir- cumstance would you perceive a white object as blue?
If you stared at a bright yellow object
for a minute or so and then looked at a white object, it would appear blue.
What is the retinex theory?
When a television set is off, its screen appears gray. When you watch a program, parts of the screen appear black, even though more light is actually showing on the screen than when the set was off. What accounts for the black perception?
The black experience arises by contrast with the brighter areas around it.
That is, visual perception requires reasoning and infer- ence, not just retinal stimulation. . Color perception depends not just on the wavelength of light from a given spot but also the light from surrounding areas.
The context can change
the color perception.
Why is color vision deficiency a better term than color
blindness?
Very few people see the world entirely in black and white. The more common condition is difficulty discriminating red from green.
What happens when you see something?
Light rays reflect off the object and strike your
retina.
the route from retinal receptors to the brain?
Receptors connect to bipolars, which connect to gan-
glion cells, which send axons to the brain.
Why is vision most acute at the fovea?
Each receptor in the fovea has a direct line to the brain.
Vision in the periphery of the retina has poor sensitivity to detail but great sensitivity to faint light. Why?
Toward the periphery, the retina has more cones and fewer rods.
Suppose you perceive something as red. According to the trichromatic theory, what is the explanation?
Light from the object has excited your long-wave- length cones more strongly than your other cones.
Color vision deficiency demonstrates which fundamental point about perception?
Color is in the brain and not in the light itself.
