Vary in their wavelength
Wavelength is the peak-to-peak distance of a wave. The human eye is able to detect electromagnetic energy with wavelengths from about 400 to 700 nanometers. This range is called the visible spectrum. As shown in the image above, there are other forms of electromagnetic energy with longer and shorter wavelengths we cannot see, such as radio waves (longer wavelengths) and X-rays (shorter wavelengths).
The colored part of the eye that controls the size of the pupil by constricting or dilating in response to light intensity.
A structure that focuses the incoming light on the retina
The process of changing the curvature of the lens to keep the light entering the eye focused on the retina.
If the lens does not focus light in the right spot, the person will have blurry vision.
120 million rods in each eye.
Located around the edges of the retina.
5 million in each eye.
Operate best in bright light.
Located around the fovea (central part of the retina).
We have no photoreceptor cells where the optic nerve leaves our eye
Our eyes are closed
Depends on the amplitude.
One type of cone reacts primarily to blue light (short wavelengths), another reacts primarily to green light (medium wavelengths), and a third reacts primarily to red light (long wavelengths).
The visual cortex then detects and compares the strength of the signals from each of the three types of cones, creating the experience of color.
If the brain is receiving primarily red and blue signals, for instance, it perceives purple; if it is receiving primarily red and green signals, it perceives yellow; and if it is receiving messages from all three types of cones, it perceives white.
This was proposed because yellow is not a mix or red and green and also people with colorblindness cannot see wither green or red. But they can see yellow.
Evidence for the opponent-process theory comes from the fact that some neurons in the retina and in the visual cortex are excited by one color (e.g., red) but inhibited by another color (e.g., green) as shown in the following figure.
Correct! The Young-Helmholtz trichromatic theory indicates that if the brain is perceiving information from primarily the red and blue cones, purple is what is perceived.
Correct! The Opponent-Process theory is based on two color contrasts (red-green and blue-yellow) and black-white contrast. Yellow is opposite of blue on the color wheel and this theory would explain seeing the opposite color as an afterimage of its opposite.
Young-Helmholz Trichromatic theory is based on three types of color receptors (blue, green, and red). The different functions of the three types of cones are apparent in those who experience color blindness (the inability to detect either green and/or red colors).
Correct! The Opponent-Process theory deals with color contrasts and how some neurons in the retina and visual cortex are excited by one color (i.e., blue) but inhibited by another color (i.e., yellow).
The Young-Helmholz Trichromatic theory is based on three types of color receptors, short waves (blue), medium waves (green), and long waves (red).
The idea of the gestalt is that the “whole is more than the sum of its parts.”
Figure and ground
We structure input such that we always see a figure (image) against a ground (background).
May see a vase or two faces, But either way you organize a figure against a ground
Stimuli that are similar to each other tend to be grouped together.
You are more likely to see three similar columns among the XYX characters at right than you are to see for rows
We tend to group nearby figures together.
Example: Do you see four or eight images at right? Principles of proximity suggest that you might see only four.
We tend to perceive stimuli in smooth, continuous ways rather than in more discontinuous ways.
Example: Most people see a line of dots that move from the lower left to the upper right, rather than a line that moves from the left and the suddenly turns down. The principle of continuity leads us to see most lines as following the smoothest possible path.
We tend to fill in gaps in an incomplete image to create a complete, whole object.
Closure leads us to see a single spherical object at right rather than a set of unrelated cones.
We wouldn’t be able to drive a car, thread a needle, or navigate through a store.
both learned and innate
crawl away from the cliff
remain on the board and cry
cross the cliff
Inward turning of our eyes that is required to focus on objects that are less than about 50 feet away from us.
Convergence provides information about depth by the angle of the eyes relative to each other.
Paths of visual information from the face of a block into the right eye and left eye.
Good job! The difference in the images sensed by the left eye and the right eye contributes to depth perception through retinal disparity.
As the lens changes its curvature to focus on distant or close objects, information relayed from the muscles attached to the lens helps us determine an object’s distance. Accommodation is only effective at short viewing distances, however, so while it comes in handy when threading a needle or tying shoelaces, it is far less effective when driving or playing sports.
We tend to see objects high up in our field of vision as father away
The fence posts at right appear father away not only because they become smaller but also because they appear higher up in the picture.
Assuming that the objects in a scene are the same size, smaller objects are perceived as father away.
Cars in the distance appear smaller than those nearer to us.
Parallel lines appear to converge at a distance.
We know that the tracks at right are parallel. When they appear closer together, we determine they are further away.
Light and shadow
The eye receives more reflected light from objects that are closer to us. Normally, light comes from above so darker images are in shadow.
We see extending and indenting according to their shadowing.
When one object overlaps another object, we view it as closer.
Because the blue star covers the pink bar, it is seen as closer than the yellow moon.
Objects that appear hazy, or that are covered with smog or dust appear father away.
The artist who painted the picture used aerial perspective to make the clouds more hazy and thus appear father away.
A series of circles are flashed on and off in sequence, though the flashing occurs more slowly than in the phi phenomenon
That’s correct! Wavelength is a property of electromagnetic energy. It is the distance from one peak of a wave to the next peak. The human eye is able to detect only those electromagnetic waves with wavelengths from approximately 400 to 700 nanometers. We call this range the visible spectrum.
That’s correct! The lens focuses light onto the retina. Muscles control the shape of the lens so rays of light are brought to a focus on the retina, forming an image of what you are looking at. When a person who is nearsighted looks at a distant object, light rays come to a focus in front of the retina, making the image the person sees seem blurry.
only the left side
only the right side
That’s correct! The visual system does not follow the principle of contralateral control completely. Since both eyes take in information from the right and left visual field, some of the optic fibers from each eye cross over so that complete images from each visual field can be processed in the visual cortex of the opposite hemisphere.
That’s correct! Cones are the type of photoreceptors in the retina that are sensitive to color and also play a major role in visual acuity. Daylight vision depends on cones.
That’s correct! The occipital lobe, located at the back of the skull, is where visual information is processed in the brain.
The information received by the two eyes is slightly different.
Our brains fill in the missing information.
Our eyes are constantly moving.
We consciously direct our eyes to pick up the information missed by the blind spot.
That’s correct. Brightness is directly related to the amplitude, or height, of a light wave. This means the higher the amplitude, the brighter the light is perceived to be.
That’s correct. The Young-Helmholtz theory states that color vision is based on our visual system having three types of cones, each of which is sensitive to either the color red, green, or blue. Mixing these primary color signals allows our brain to perceive many, many different colors. Red-green color blindness can be explained by the Young-Helmholtz theory because it proposes the red and green cones are not functioning properly.
Although the coins are close to each other, the similarity feature of the pennies and the quarters makes you group them together and perceive two rows of coins
The extent to which it is learned varies by individual
It is exclusively learned
It is both learned and innate
It is exclusively innate
That’s correct! Different studies have shown that depth perception is both innate and learned.
monocular depth cue
binocular depth cue
That’s correct! Convergence describes the inward turning of both eyes in order to focus on an object that is less than about 50 feet away.
light and shadow
Position is a monocular depth cue; however it refers to our tendency to see objects higher up in our field of vision as farther away. This scenario is an example of the relative size cue.
That’s correct! Convergence is a binocular method of perceiving the depth of an object based on the inward turning of both eyes in order to focus on the same object.
the beta effect
the phi phenomenon
That’s correct! The beta effect is the perception of motion that occurs when different images are presented next to each other with a short amount of time in between.