People who are blind use vision to gather information about their environment.
There are several steps in the process of vision.
You should have a basic understanding of the structures and processes involved for the AP test.
Light is reflected off objects and gathered by the eye.
You may have studied visible light in your science class.
There are a number of factors that affect the color we perceive.
Light intensity is one.
The light contains a lot of energy.
The object's brightness is determined by this factor.
The particular hue we see is determined by the light wavelength.
Wavelengths are longer than visible light.
Ultra violet waves and X-rays are shorter than visible light.
There are different colors within the visible light spectrum.
The colors of the visible spectrum are red, orange, yellow, green, blue, indigo, and violet.
You get white light or sunlight when you mix all the light waves together.
When we think of objects as having colors, we think of a red shirt and a blue car.
A red shirt reflects light.
The objects reflect all of the light's wavelength.
The reflected light from the object enters our eye when we look at it.
Refer to Figure 4.1 for structures in the eye.
The light enters the eye through a protective covering.
The light is focused by the cornea.
The light goes through the eye.
The shutter of a camera has a pupil.
The muscles that control the iris open it to let more light in and also make it smaller to let less light in.
The light that enters the eye is focused by the lens, which is flexible and curved.
Try to focus on one finger at a time.
Change your focus and look at the wall behind you.
As you switch your focus, you can feel the muscles changing the shape of your lens.
The image is inverted when the light passes through the lens.
The focused inverted image projects a screen on the back of your eye.
The screen has specialized neurons that are activated by different colors of light.
The translation of incoming stimuli into neural signals is referred to as transduction.
This term applies to all of our senses.
Light stimulates the cells in the retina.
There are several layers of cells in the eye.
Light illuminates the first layer of cells.
The cells that respond to black and white are cones and rods.
The cells are arranged in a pattern.
The ratio of rods to cones is twenty to one.
Cones are in the center of the eye.
The fovea contains the highest concentration of cones in the center of the eye.
If you focus on something, you can see the light reflected off of your fovea.
Your peripheral vision is mostly black and white.
Your peripheral vision seems to be full color, but controlled experiments show otherwise.
A friend will hold different colored pens in your peripheral vision if you focus on a spot in front of you.
The next layer of cells in the retina are activated if enough rods and cones fire.
The next layer of cells, ganglion cells, are activated if enough bipolar cells fire.
The axons of the ganglion cells are located in the thalamus.
The messages are sent to the visual cortices in the brain.
The blind spot is where the nerve leaves the eye, and it has no cones or rods.
The brain is divided into two parts.
The left side of the brain contains impulses from the left side of the retina.
From the right side of the brain goes impulses from the right side of the retina.
The spot where the nerves cross each other is called the optic chiasm.
This is a simplified version of the process.
This explanation is suitable for our purposes, as different factors are involved in why each layer of cells might fire.
The visual cortex of the brain is located in the occipital lobe, according to the "Biological Bases" chapter.
According to some researchers, sensation ends and perception begins at this point.
The layers of cells in the retina are believed to have some interpretation of images.
Others say it happens in the thalamus.
The visual cortex of the brain receives impulses from the cells of the retina, and the impulses are activated by feature detectors.
The researchers discovered that the visual cortex responds to different types of visual images.
The visual cortex has many feature detectors for images.
A combination of these features is what we see.
There are competing theories about how we see color.
The Young-Helmholtz Trichromatic (three color) theory is the oldest and most simple theory.
The primary colors of light are blue, red, and green, which are detected by cones in the retina.
All the colors of the visible spectrum can be produced by different combinations of these cones.
This theory has some research support and makes sense, but it can't explain some visual phenomena, such as afterimages and color blindness.
You can see a color afterimage if you stare at one color for a while and then look at a white or blank space.
The after image of green will be red, while the after image of yellow will be blue.
It's similar to color blindness.
People with dichromatic color blindness can't see either red or green shades.
There is a need for another theory of color vision.
According to the opponent-process theory, there are red, green, yellow, and blue sensoryreceptors in the retina.
If one sensor is stimulated, the other is not able to fire.
The theory explains color after images.
If you stare at red for a long time, you will fatigue the sensors.
When you look at a blank page, the opponent part of the pair for red will fire, and you will see a green afterimage.
The opponent-process theory explains colorblindness.
If an individual is missing one pair of color sensors, he or she should have difficulty seeing the colors.
People with dichromatic color blindness can't see shades of red and green.
A combination of trichromatic and opponent-process theory is agreed upon by most researchers.
Individual cones correspond best to the trichromatic theory, while opponent processes may occur at other layers of the retina.
Both concepts are needed to fully explain color vision.
Sound waves are not the same as waves in the form of energy, but they are the same as waves in the air.
Sound waves are created by vibrating in the air and being collected by our ears.
The neural messages are sent to the brain through the process of transduction.
Sound waves have different frequencies and amplitudes.
Amplitude is the height of the wave and determines the sound's loudness.
The pitch is measured in megahertz by the length of the waves.
Waves are packed with high-pitched sounds.
Waves are separated by low frequencies and low-pitched sounds.
The waves travel down the ear canal until they reach the eardrum.
The sound waves hit the thin membranes and it vibrates.
The ossicles are three small bones that are attached to a membrane.
The hammer is connected to the anvil and the stirrup is connected to the eardrum.
The three bones transmit the sound of the eardrum to the window.
The cochlea is a structure that is shaped like a snail's shell.
The cochlea floor has a basilar membrane.
It is lined with hair cells that are connected to the organ of Corti.
The brain receives impulses from the organ of Corti.
One way to remember is to imagine you are watching waves.
Waves come by at a Frequency.
The waves are high if they speed by quickly.
Amplitude is the height of the waves.
Two different theories describe the processes involved in hearing pitch.
The hair cells in the cochlea respond to different frequencies of sound based on where they are located.
Some bend in response to high pitches.
The hair cells move in different places in the cochlea.
According to research, place theory accurately describes how hair cells sense the upper range of pitches.
The cells fire at a certain rate.
The hair cells fire at different rates in the cochlea.
Hearing problems can be explained by understanding how hearing works.
Conduction deafness occurs when something goes wrong with the system of conducting the sound to the cochlea.
My mother-in-law has a medical condition that is causing her stirrup to degrade slowly.
She will need to have that bone replaced in order to hear well.
Hearing loss occurs when the hair cells in the cochlea are damaged.
If you have ever been to a concert, football game, or other event that was loud enough to cause permanent damage to your hearing, you should get it checked out.
The hair cells in your cochlea can be permanently damaged by exposure to loud noise.
Nerve deafness is more difficult to treat since no method has been found that will encourage hair cells to regrowth.
Our sense of touch is activated when our skin is pierced, or when we experience a change in temperature.
The relationship between different types of nerve endings and the sense of touch is not fully understood.
Nerve endings respond to pressure and temperature.
Our brain interprets the amount of temperature change as the intensity of the touch, from a light touch to a hard blow.
The touch is placed on our body where the nerve endings fire.
Different parts of our body have different nerve endings.
If we want to feel something, we usually use our finger, an area of high nerve concentration, rather than the back of our elbow, an area of low nerve concentration.
A different kind of nerve endings called pain receptors will also fire if touch or temperature are stimulated sharply.
It warns us of potential dangers and that's why pain is useful.
Gate-control theory explains how we experience pain.
Some pain messages have a higher priority than others.
When a higher priority message is sent, the gate swings open for it and shuts for a low priority message, which we will not feel.
The gate is a convenient way to understand how pain messages are sent.
When you scratch an itch, the gate swings open for high-intensity scratching and shut for low-intensity itching, and you can stop itching for a short period of time.
Endorphins swing the gate shut.
Natural endorphins in the brain are similar to opiates.
Light and sound waves can be seen through the eyes of the chemical senses.
The bumps on your tongue are the taste buds.
There are taste buds on the tongue, cheeks, and roof of the mouth.
Humans sense five different types of tastes.
Some taste buds respond more strongly to a taste than others.
People have different abilities to taste food.
The more densely packed the taste buds, the more chemicals are absorbed.
You can see how densely packed buds taste by looking at the papillae on your tongue.
If the bumps are tightly packed together, you will like the food.
You are probably a weak taster if they are spread apart.
The combination of taste and smell is what we think of as the flavor of food.
Chemicals emitted by substances affect our sense of smell.
Some of them get into our nose.
The molecules are absorbed by the cells at the top of each nostril.
The taste buds are the type of cells that are not yet known.
Some researchers think there may be as many as 100 different types of smell receptors.
The olfactory bulb's nerve fibers connect to the brain differently than other senses.
Information from our sense of smell goes directly to the amygdala and then to the hippocampus before it goes to the cortex.
A direct connection to the limbic system may explain why smell is so powerful.
Our body is oriented in space thanks to our vestibular sense.
The canals are filled with fluid.
The fluid in the canals moves when the position of your head changes.
The hair cells move and their impulses go to the brain.
When the fluid in these canals is agitated, it can cause nausea and dizziness.
During an exciting roller-coaster ride, the fluid in the canals might move so much that the brain receives confusing signals about body position.
The reaction to this causes dizziness and nausea.
Our kinesthetic sense gives us feedback about the position and orientation of specific body parts, while our vestibular sense keeps track of the overall orientation of our body.
Our brain gets information from our muscles and joints.
We can keep track of our body with this information and visual feedback.
If you reach down with one finger and touch your kneecap with a high degree of accuracy, your kinesthetic sense will tell you where your finger is in relation to your kneecap.
See the table for a summary of the senses.
perception is the process of understanding and interpreting sensations.
The study of the interaction between sensations and our experience of them is called psychophysics.
Researchers trying to uncover the rules our minds use to interpret sensations.
We will look at some basic perceptual rules for vision.
Research shows that our senses have limits.
The smallest amount of stimuli we can detect is the absolute threshold.
A single candle flame is estimated to be the smallest amount of light we can detect, which is 30 miles away on a dark night.
A single drop of perfume could be detected by most of us.
The technical definition of absolute threshold is the minimal amount of stimuli we can detect, because researchers try to take into account individual variation in sensitivity and interference from other sensory sources.
Stimuli below our absolute threshold is said to be subliminal.
Some companies claim that they can change behavior.
Their claim is not supported by psychological research.
Sometimes subliminal messages can affect behavior in subtle ways, such as choosing a word at random from a list after the word was presented subliminally.
There is no evidence that subliminal messages such as "lose weight" are effective.
The placebo effect is more likely to change behavior than the subliminal message is.
This change is defined by the difference threshold.
The difference threshold is the smallest amount of change needed before we can detect a change.
The Weber-Fechner law is named after psychophysicist Gustav Fechner and is named after Weber's law.
The change needed is proportional to the original intensity.
It will need to change before we notice a difference.
If someone adds a small amount of cayenne pepper to a dish that is normally not very spicy, you would need to add a lot more hot pepper to make it more spicy.
Weber discovered that the constants differ between the senses.
5 percent is the constant for hearing.
If you listened to a 100decibel tone, the volume would have to increase to 105 decibels before you noticed that it was louder.
Weber has a constant vision of 8 percent.
Adding 8 candles to 100 candles would make it look brighter.
Several theories are used by psychologists to describe how we see the world.
These theories are not competing with each other.
There are different examples or parts of perception described in each theory.
Sometimes a single example of the interpretation of sensation needs to be explained using all of the following theories.
Real-world examples of perception are more complex.
The effects of distraction and interference on our perception of the world is investigated by signal detection theory.
Predicting what we will perceive among competing stimuli is the focus of this area of research.
The motivation to detect certain stimuli and what we expect to see are taken into account in signal detection theory.
The factors are called response criteria.
If I am hungry and enjoy the taste of rhubarb, I will be more likely to smell a freshly baked pie.
signal detection theory tries to explain and predict the different perceptual mistakes we make.
A false positive is when we think there isn't anything.
You may think you see a friend on a crowded street and end up waving at a stranger.
A false negative is not seeing something.
The directions at the top of the test tell you not to write on the form.
One type of error is more serious than the other, and this can affect perception.
A false negative is a more serious mistake than a false positive, even though both mistakes are important.
When we use top-down processing, we fill in gaps in what we see.
I _ope yo_ _et a 5 on t_ A_ e_am.
You used the context of the sentence to see the blanks as the right letters.
When you use your background knowledge, you fill in gaps in what you see.
Our experience makes mental representations of how we expect the world to be.
The world is influenced by how we perceive it.
A perceptual set is a predisposition to perceive something in a certain way.
You have experienced top-down processing if you have seen images in the clouds.
You can use your background knowledge to see the random shapes of clouds.
Backmasking was a concern of some parent groups in the 70s.
The parent groups would play song lyrics backwards and hear threatening messages.
The effects of backmasking were demanded by some groups of parents.
Random noise is what the lyrics played backward are.
If you expect to hear a threatening message in the random noise, you will most likely see an image in the clouds.
People who listened to the songs played backwards perceived the threatening messages due to top-down processing.
Top-down processing is the opposite of bottom-up processing.
We use the features of the object itself to build a complete perception instead of using our experience.
We start our perception at the bottom with the individual characteristics of the image and put them all together into our final perception.
It is an automatic process that can be hard to imagine.
Basic features of objects, such as horizontal and vertical lines, curves, motion, and so on, can be seen by feature detectors in the visual cortex.
These basic characteristics are used to build the picture from the bottom up.
We use both bottom-up and top-down processing when we see the world.
Bottom-up processing takes longer but is more accurate than top-down processing.
There are too many rules to cover in this book.
Some of the basic rules are important for the AP psychology exam.
The figure-ground relationship is one of the first perceptual decisions we must make.
There are several optical illusions that play with this rule.
The principles that govern how we perceive groups of objects were described by a group of researchers.
The psychologists said that we normally see images as groups.
They thought the process was inevitable.
There are a number of factors that influence how we group objects.
Our changing angle of vision, variations in light, and so on, causes objects to change from moment to moment.
Our ability to maintain a constant perception of an object is called constancy.
There are different types of constancy.
Our ability to gauge motion is another aspect of perception.
Our brains can detect how fast images move across our eyes, and they can also take into account our own movement.
Our brains perceive objects to be moving when they are not.
The stroboscopic effect is used in movies and flip books.
A series of still pictures presented at a certain speed will appear to be moving.
The phi phenomenon is an example of a movie marquee with holiday lights.
A series of lightbulbs are turned on and off at the same time.
The autokinetic effect is a third example.
People will report seeing a spot of light projected onto a wall of a dark room if they are asked to stare at it.
One of the most important parts of visual perception is depth.
Without depth perception, we wouldn't be able to differentiate between what is near and what is far.
The limitation could be dangerous.
The visual cliff experiment was used to determine when human infants can perceive depth.
An infant is placed on one side of a table that looks like a cliff.
The infant cannot possibly fall because the glass extends across the entire table.
An infant that is old enough to crawl won't crawl across the cliff because of their depth perception.
Experiments show that depth perception develops when we are three months old.
The monocular and binocular cues that we use to perceive depth are divided into two categories.
You have learned monocular depth cues if you have taken a drawing class.
Artists use the cues to imply depth in their drawings.
Linear perspective is one of the most common cues.
If you wanted to draw a railroad track that runs away from the viewer off into the distance, most likely you would start by drawing two lines that intersect at the top of your paper.
You could use the relative size cue if you added a drawing of the train.
The boxcars are larger than the engine in the distance.
A water tower blocking our view of part of the train would be seen as closer to us due to the interposition cue, objects that block the view to other objects must be closer to us.
If the train ran through a desert landscape, you could draw the rocks closest to the viewer in detail, while the landscape off in the distance would not be as detailed.
We know that we can see details in texture close to us, but not far away.
Your art teacher might teach you how to use shadow in your picture.
By shading part of your picture, you can say where the light source is and how deep it is.
The ability to perceive depth is due to the fact that we see the world with two eyes.
The first binocular cue-- binocular disparity-- is demonstrated by the finger trick you read about.
Our eyes look at an object from a different angle.
The brain has two images.
The closer the object is, the more disparity there will be between the images coming from each eye.
convergence is the other binocular cue.
As an object gets closer to our face, our eyes must move towards each other to keep focused on the object.
The brain gets feedback from the muscles controlling eye movement and knows that the closer the eyes are, the closer the object is.
The effect of culture on perception is being investigated by psychologists.
Some of the perceptual rules psychologists thought were innate are actually learned.
Cultures that don't use monocular depth cues in their art don't see the depth in pictures.
Some optical illusions are seen differently by people from different cultures.
There is a representation of the Muller-Lyer illusion.
Even though both lines are the same length, Line A should look longer.
The Muller-Lyer illusion is not usually used by people who come from noncarpentered cultures.
Some basic perceptual sets are learned from our culture.
If you've reviewed the senses and how the brain changes these sensations into perceptions, you can interpret the term extrasensory perception in a more specific way than most people can.
ESP claims are not accepted by psychologists because they don't find reliable evidence that we can perceive sensations other than through our sight, smell, hearing, taste, and balance systems.
Double-blind studies are used by researchers to find other explanations for ESP claims.
ESP claims can be better explained by deception, magic tricks or coincidence.
Five suggested answers or completions are followed by each of the questions or incomplete statements.
Pick the one that is the best.
In a perception research lab, you are asked to describe the shape of the top of a box as the box is slowly rotating.
You are shown a picture of your grandfather's face, but his eyes and mouth are not visible.