Psych Unite 5:module 10

Electromagnetic energy
Pulses of energy waves that can carry information from place to place

Vary in their wavelength

Wavelength
Distance between one wave peak and the next wave peak
The property that differentiates the part of the electromagnetic spectrum that we can see from the part we cannot see is __________________.

intensity

color

wavelength

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).

A wavelength is measured by the _____________ between one wave peak and the next wave peak.

volume

distance

height

Distance
Cornea
A clear covering that protects the eye and begins to focus the incoming light.
Pupil
A small opening in the center of the eye that allows light to enter the eye.
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Iris
Surrounds the pupil

The colored part of the eye that controls the size of the pupil by constricting or dilating in response to light intensity.

Light’s path through the eye
Through the cornea, passing through the pupil, which is surrounded by the iris.
Lens
Behind the pupil

A structure that focuses the incoming light on the retina

Retina
The layer of tissue at the back of the eye that contains photoreceptor cells.
Accommodation
As our eyes move from near objects to distant objects.

The process of changing the curvature of the lens to keep the light entering the eye focused on the retina.

Nearsighted
When the focus is in front of the retina.
Farsighted
When the focus is behind the retina.
Which structure of the eye determines whether a person has abnormal vision (e.g., is nearsighted or farsighted)?

Retina

Eye muscles

Pupil

Lens

Lens

If the lens does not focus light in the right spot, the person will have blurry vision.

What area of the eye controls the size of the pupil?

Lens

Iris

Cornea

Retina

Iris
What part of the eye contains photoreceptor cells?

Pupil

Cornea

Lens

Retina

Retina
When light falls on the retina it first activates?
Receptor cells known as rods and cones.
Optic nerve
A collection of millions of ganglion neurons that sends cast amounts of visual information via. the thalamus to the brain.
Rods
Visual neurons that specialize in detecting black, white and gray colors.

120 million rods in each eye.

Located around the edges of the retina.

Cones
Are visual neurons that are specialized in detecting fine detail and colors.

5 million in each eye.

Operate best in bright light.

Located around the fovea (central part of the retina).

Why do we experience this blind spot?

Bad vision

We have no photoreceptor cells where the optic nerve leaves our eye

Our eyes are closed

We have no photoreceptor cells where the optic nerve leaves our eye
Detector neurons
Apecialized neurons, located in the visual cortex, that respond to the strength, angles, shapes, edges, and movements of a visual stimulus.
Why don’t we have a gap in our vision due to our blind spot?
There are three reasons. First, our eyes are constantly moving, so they take in information from different locations. Second, one eye takes in information that the other eye misses. Third, our visual cortex fills in what is missing.
Blind spot
(the place where the optic nerve leaves the retina)
Visual cortex
Made up of specialized neurons that turn the sensations they receive from the optic nerve into meaningful images.
Shade of color
A hue, which is conveyed by the wavelength of the light that enters the eye.
Detect brightness
From the intensity or the wave. (Bigger or more intense waves are perceived as brighter)

Depends on the amplitude.

Hermann von Helmhotlz (1821-1894)
Theorized that color is perceived because the cones in the retina come in three types.

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.

Young-Helmholtz trichromatic color theory
What color we see depends on the mix of the signals from the three types of cones.

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.

Opponent-process color theory
Alternative theory to Young-Helmholtz theory we analyze sensory information not in terms of three colors but rather in three sets of “opponent colors”: red-green, yellow-blue, and white-black.

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.

Perceiving purple is a result of receiving messages from two types of cells: those that perceive red and those that perceive blue.

Young-Helmholtz

Opponent-process

Young-Helmholtz

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.

Afterimages caused by staring at a blue image then looking away makes you perceive yellow.

Young-Helmholtz

Opponent-process

Opponent-process

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.

Many people who are colorblind cannot distinguish red from green.

Young-Helmholtz

Opponent-process

Correct! The Young-Helmholtz

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).

Neurons in the retina are excited by one color but inhibited by another color.

Young-Helmholtz

Opponent-process

Opponent-process

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).

There are three types of cone cells, one for each primary color.

Young-Helmholtz

Opponent-process

Young-Helmholz

The Young-Helmholz Trichromatic theory is based on three types of color receptors, short waves (blue), medium waves (green), and long waves (red).

Gestalt
A meaningfully organized whole.

The idea of the gestalt is that the “whole is more than the sum of its parts.”

Principle:
Figure and ground
Description:
We structure input such that we always see a figure (image) against a ground (background).

Example:
May see a vase or two faces, But either way you organize a figure against a ground

Principle:
Similarity
Description:
Stimuli that are similar to each other tend to be grouped together.

Example:
You are more likely to see three similar columns among the XYX characters at right than you are to see for rows

Principle:
Proximity
Description:
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.

Principle:
Continuity
Description:
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.

Principle:
Closure
Description:
We tend to fill in gaps in an incomplete image to create a complete, whole object.

Example:
Closure leads us to see a single spherical object at right rather than a set of unrelated cones.

Depth perception
The ability to perceive three-dimensional space and to accurately judge distance.

We wouldn’t be able to drive a car, thread a needle, or navigate through a store.

Research on the development of depth perception suggests that it is ___________.

learned

innate

both learned and innate

Both learned and innate
Research by Gibson and Walk on the visual cliff found that most infants did not ___________.

crawl away from the cliff

remain on the board and cry

cross the cliff

Cross the cliff
Binocular depth cues
Depth cues that are created by retinal image disparity—that is, the space between our eyes, and thus require the coordination of both eyes.
Convergence
An important binocular depth cue

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.

For each image, identify the binocular depth cue.

Paths of visual information from the face of a block into the right eye and left eye.

1.Retinal disparity

2.Accommodation

3. Convergence

1. Retinal disparity

Good job! The difference in the images sensed by the left eye and the right eye contributes to depth perception through retinal disparity.

Visual system also uses Accommodation
Accommodation works by messages relayed by the muscles that control the lens; how much these muscles adjust provide clues to how far away the object is.

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.

Monocular depth cues
Depth cues that help us perceive depth using only one eye.
Monocular depth cues that help us judge depth at a distance.

Name:
Position

Description:
We tend to see objects high up in our field of vision as father away

Example:
The fence posts at right appear father away not only because they become smaller but also because they appear higher up in the picture.

Monocular depth cues that help us judge depth at a distance.

Name:
Relative size

Description:
Assuming that the objects in a scene are the same size, smaller objects are perceived as father away.

Example:
Cars in the distance appear smaller than those nearer to us.

Monocular depth cues that help us judge depth at a distance.

Name:
Linear perspective

Description:
Parallel lines appear to converge at a distance.

Example:
We know that the tracks at right are parallel. When they appear closer together, we determine they are further away.

Monocular depth cues that help us judge depth at a distance.

Name:
Light and shadow

Description:
The eye receives more reflected light from objects that are closer to us. Normally, light comes from above so darker images are in shadow.

Example:
We see extending and indenting according to their shadowing.

Monocular depth cues that help us judge depth at a distance.

Name:
Interposition

Description:
When one object overlaps another object, we view it as closer.

Example:
Because the blue star covers the pink bar, it is seen as closer than the yellow moon.

Monocular depth cues that help us judge depth at a distance.

Name:
Aerial perspective

Description:
Objects that appear hazy, or that are covered with smog or dust appear father away.

Example:
The artist who painted the picture used aerial perspective to make the clouds more hazy and thus appear father away.

Apparent motion
The cues that the brain uses to perceive motion.
phi phenomenon
At the right speed, your brain creates a blur that seems to move back and forth between the two circles.

A series of circles are flashed on and off in sequence, though the flashing occurs more slowly than in the phi phenomenon

beta effect
At slower change rates this can produce the experience of a moving image.
What differentiates light energy we can perceive visually from light energy we cannot perceive visually?

Depth

Wavelength

Intensity

Color

Wavelength

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.

The _________ is a muscle that regulates the size of the pupil.

iris

cornea

fovea

retina

Iris
When a person is nearsighted, the ______ focuses light from objects far away in front of the _____, instead of on it.

lens; retina

iris; cornea

lens; cornea

pupil; retina

lens; retina

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.

Information from the left eye is processed on __________ of the visual cortex.

only the left side

only the right side

both sides

both sides

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.

Which type of neural cell is responsible for color vision?

Cones

Bipolar

Rods

Ganglion

Cones

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.

In which lobe of the brain is visual information processed?

Temporal

Parietal

Occipital

Frontal

Occipital

That’s correct! The occipital lobe, located at the back of the skull, is where visual information is processed in the brain.

Which is not a good explanation of why we don’t notice a “hole” in our visual field due to our blind spot?

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.

We consciously direct our eyes to pick up the information missed by the blind spot.
Light energy with very high amplitude would be perceived as ___________

very dim

very bright

blue

red

very bright

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.

The Young-Helmholtz theory best explains __________.

motion perception

red-green colorblindness

depth perception

visual afterimages

red-green colorblindness

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.

Amy lines up 5 pennies in a row from left to right. Below each penny, she places a quarter. You are likely to perceive this as two rows of coins, rather than 10 separate objects because of the principle of ___________.

figure-ground

closure

similarity

proximity .

Similarity

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

What is most accurate regarding the development of depth perception?

The extent to which it is learned varies by individual

It is exclusively learned

It is both learned and innate

It is exclusively innate

It is both learned and innate

That’s correct! Different studies have shown that depth perception is both innate and learned.

Convergence is an example of a(n) ___________.

monocular depth cue

learned cue

binocular depth cue

motion 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.

You look out the window, and a tree appears to be very small, about the same size as your hand. You know that this means the tree must be quite far away because of the depth cue known as __________.

relative size

light and shadow

position

linear perspective

relative size

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.

Judging the distance of a nearby object based on the angle your eyes are turned towards each other uses the depth perception cue known as __________.

relative size

accommodation

retinal disparity

convergence

convergence

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.

When two images near each other are presented in succession, we perceive that it is one object that has moved. This is known as ___________.

retinal disparity

the beta effect

the phi phenomenon

accommodation

the beta effect

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.