# 5.3 Vision  (Page 4/30)

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Our world is three-dimensional, so it makes sense that our mental representation of the world has three-dimensional properties. We use a variety of cues in a visual scene to establish our sense of depth. Some of these are binocular cues , which means that they rely on the use of both eyes. One example of a binocular depth cue is binocular disparity    , the slightly different view of the world that each of our eyes receives. To experience this slightly different view, do this simple exercise: extend your arm fully and extend one of your fingers and focus on that finger. Now, close your left eye without moving your head, then open your left eye and close your right eye without moving your head. You will notice that your finger seems to shift as you alternate between the two eyes because of the slightly different view each eye has of your finger.

A 3-D movie works on the same principle: the special glasses you wear allow the two slightly different images projected onto the screen to be seen separately by your left and your right eye. As your brain processes these images, you have the illusion that the leaping animal or running person is coming right toward you.

Although we rely on binocular cues to experience depth in our 3-D world, we can also perceive depth in 2-D arrays. Think about all the paintings and photographs you have seen. Generally, you pick up on depth in these images even though the visual stimulus is 2-D. When we do this, we are relying on a number of monocular cues , or cues that require only one eye. If you think you can’t see depth with one eye, note that you don’t bump into things when using only one eye while walking—and, in fact, we have more monocular cues than binocular cues.

An example of a monocular cue would be what is known as linear perspective. Linear perspective refers to the fact that we perceive depth when we see two parallel lines that seem to converge in an image ( [link] ). Some other monocular depth cues are interposition, the partial overlap of objects, and the relative size and closeness of images to the horizon.

## Stereoblindness

Bruce Bridgeman was born with an extreme case of lazy eye that resulted in him being stereoblind, or unable to respond to binocular cues of depth. He relied heavily on monocular depth cues, but he never had a true appreciation of the 3-D nature of the world around him. This all changed one night in 2012 while Bruce was seeing a movie with his wife.

The movie the couple was going to see was shot in 3-D, and even though he thought it was a waste of money, Bruce paid for the 3-D glasses when he purchased his ticket. As soon as the film began, Bruce put on the glasses and experienced something completely new. For the first time in his life he appreciated the true depth of the world around him. Remarkably, his ability to perceive depth persisted outside of the movie theater.

There are cells in the nervous system that respond to binocular depth cues. Normally, these cells require activation during early development in order to persist, so experts familiar with Bruce’s case (and others like his) assume that at some point in his development, Bruce must have experienced at least a fleeting moment of binocular vision. It was enough to ensure the survival of the cells in the visual system tuned to binocular cues. The mystery now is why it took Bruce nearly 70 years to have these cells activated (Peck, 2012).

## Summary

Light waves cross the cornea and enter the eye at the pupil. The eye’s lens focuses this light so that the image is focused on a region of the retina known as the fovea. The fovea contains cones that possess high levels of visual acuity and operate best in bright light conditions. Rods are located throughout the retina and operate best under dim light conditions. Visual information leaves the eye via the optic nerve. Information from each visual field is sent to the opposite side of the brain at the optic chiasm. Visual information then moves through a number of brain sites before reaching the occipital lobe, where it is processed.

Two theories explain color perception. The trichromatic theory asserts that three distinct cone groups are tuned to slightly different wavelengths of light, and it is the combination of activity across these cone types that results in our perception of all the colors we see. The opponent-process theory of color vision asserts that color is processed in opponent pairs and accounts for the interesting phenomenon of a negative afterimage. We perceive depth through a combination of monocular and binocular depth cues.

## Personal application question

Take a look at a few of your photos or personal works of art. Can you find examples of linear perspective as a potential depth cue?

#### Questions & Answers

because psychology is a natural science as well as a science. it's a interdisciplinary subject
Kamakshi Reply
yes absolutely we cabt out Psychology completely into science dur to its various measuring aspects
utkarsh
cannot* put*
utkarsh
Assess the relationship between heredity and environment in human development
Newman Reply
जिवन कक्षा विकासाच्या एकूण किती अवस्था आहेत
Digambar Reply
what happened Digambar?
sakshi
?
Reina
Is here anybody exactly awared about the medicine used for the schizophrenia?
Fazil
plz can i know if io psychology in demand ou it's better to continu in human resourses management?
Reina
there are many drugs used to alleviate the symptoms, but none are used for curing the disorder itself.
Rupert
Researchers believe that one important function of sleep is to facilitate learning and memory. How does knowing this help you in your college studies? What changes could you make to your study and sleep habits to maximize your mastery of the material covered in class?
whitecat Reply
Well, for starters, both are entirely different aspect for consideration. As a college student, having an adequate amount of sleep is relatively rare especially on instances where we are totally forced to stay all night (whether for studying or doing academic works).
Rupert
benefits of physcology
Irfan Reply
who define first physcology
Irfan
who define first physcology
Irfan
I think it was either Henry James Or William James are the father of psychology.
James
I haven't read the flash cards and memorized them sense 2015.
James
so iv forgotten some info and some has never left me . I'm very passionate about psychology.
James
I study medical psychology
John
the history of psychology usually traces back to ancient chinese practices. but modern times acknowledge Wilhelm Wundt as the first person to establish a school.of thought in psychology.
Rupert
huh
ANGELICA
is it wrong?
Rupert
please can i know what is the difference about io psychology and human resources managment and which is more in demand ?
Reina Reply
What is psychology
Tayyeba Reply
someone who can observe or understand a person's reactions.
Leanne
It is the scientific study of behavior and mental processes
Enos
Sarah is a 30 year old white female. Her occupation is part time chef. She is recently been divorced and has custody of her three children. She has extreme changes in her mood that began to appear in her 20’s but she never went to see a doctor about them. When family tries to talk to her about her u
Ere Reply
listen very carefully for red flags on both sides
Leanne
what does historical racism mean
Unasumming Reply
Means that racism was present in a group of peoples race in there past and maybe even now. Example is the Native Americans and African Americans also Asian people. Anyone of not caucasian resent. So people who are mixed races also experience rascism.
James
racism meaning I would believe is a negative impact on other separate cultures, causing some serious concerns to the human race.
Leanne
How do counsel someone that is kinda depressed, lonely and stuffs but the person is pushing you away with by saying stuffs you don't like? Your age mate
Ajayi Reply
let them figure themselves out met them come to you and listen more than speak
Jascelyn
don't take anything too personal someone who is depressed has more feelings other than being sad. I have been through it we dont alwaya mean the things we say. just give time and space but be there when they are ready.
Deanna
the person should be first dealt with very patience and understanding.......... person's trust should be won first to treat that kind of state if counsel is the priority..... don't rush small steps will lead to get successful results....... after the patient start trusting you conversate with them.
Amisha
OK..... Thank you very much It makes me look desperate for the person's attention Thanks tho
Ajayi
just let them know even if they aren't ready to tall right now, you will be here for them whenever they are.
Deanna
we need to wait till the stage comes when he/ she is ready at mental level to participate as he is the subject and the core of the part of that particular conscelling session
aaqib
A.Are they saying it in general manner or B.they are saying it cz they know something about you personally If it is A. then remember it's a part of counseling...even if you don't agree with their views..it is theirs.. so don't take it personally
PREETI
if it is B. tell them .. we are here to talk about them not you Also remember people takes time with things.. so it does get difficult at times.. but in counseling it's about them not you. And if it affecting you much .. see why is there .. and try to objective about it OR refer them to someone
PREETI
allow them time to always become comfortable by listening to all sorts of thoughts they all sound scattered but if you ,just let it go until their ready to ask for advice ,my thoughts of counciling would go for a few more sessions of them venting until they've had enough to feel they want geedback
Leanne
what is the trait in the given example?
Maya Reply
what's the given example?
SamieMike
my fat cock
Andrea
o.o u seem like u need to read this txt
SamieMike
learning to understand psychological effects of one's mind thoughts
Leanne
mental state and behavior
Mufakir Reply
Feared ,lethargic, self isolated...
Leanne
because psychology basic is observation asa well as science, so people might skeptical about these two but if we look into it people might notice that it's different because psychology is study about mind and science is study about many thing around us and it's not study about mind clearly.
Karona Reply
empirical method is the method of observation on object rather than do experiment .
Karona
ology is the study of theory .
Karona
psyche means soul as well as butterfly.
Karona
psychology is the the study of mind and behavior
Karona
this is where I'm a little sceptical. we learning psychology based on books. but we ourselves r also human. when we to encounter a real life situation how well can we act accordingly
Aileen
im curious more of myself then others
Aileen
psychology is the scientific study of mind and behavior. scientific mean it's based on observation and experiments. yeah we can observe behavior easily but can't read mind directly that's why we do observe behavior and apply test and therapies to study mind basically we behave according to our mind
Faiza
educates a humans thoughts to expand and explore more of how far a mind will go if allowed
Leanne
wilhelm wundt studied psychology for the purpose of
Rufai Reply
i dont know, all inknow is that he pioneered the practice of introspective and his school of thought aims to study behavior as structured elements
Rupert
what are the personality traits
Elnestine Reply
1. The theory classified & identifies that there are five personality traits; 1. Openness to experience 2. Conscientious 3. Extraversion 4. Agreeable 5. Neuroticism
Rodney

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Source:  OpenStax, Psychology. OpenStax CNX. Feb 03, 2015 Download for free at https://legacy.cnx.org/content/col11629/1.5
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