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Seeing Eye

Seeing Eye

Guide dogs are assistance dogs especially trained to lead blind or visually impaired people around obstacles. They are commonly but incorrectly called "Seeing Eye" dogs, since Seeing Eye is the name of only one of many guide dog training schools. These dogs spend their early lives in foster homes where they are socialized through exposure to loving attention, and taught rudimentary skills through obedience training. Once potential guide dogs reach a certain age, they then begin their schooling as assistance animals before being matched with compatible human partners. These matches are cemented through a 30-day training course, wherein the human half of the team learns to control the dog and interpret its signals. Very few visually impaired people go through this training, and these candidates must already have fully developed orientation and mobility skills before they do. orientation and mobility orientation and mobility Dogs are partially (red-green) color blind and so guide dogs cannot see colors the way people do, nor are they able to interpret street signs. The human half of the guide dog team does the leading, based upon skills acquired through previous mobility training. In several countries, guide dogs are exempt from regulations against the presence of animals in places such as restaurants and public transportation.

History

The first guide dog training schools were established in Germany during the First World War, to enhance the mobility of returning veterans who were blinded in combat. The United States followed suit in 1929 with the Seeing Eye in Morristown, New Jersey. This school was followed, two years later, by the British Guide Dog Association.

Breeds

Early on, trainers recognized which breeds produced dogs with the most appropriate temperaments for this work, so that, now, Golden Retrievers, Labradors and sometimes German Shepherd Dogs, are more likely than dogs of other breeds to be chosen, although by no means does this indicate that only these three are appropriate (for example, Boxers are also used but as they have a long adolescence they are less common.) The preferred breed is a Golden Retriever / Labrador cross because both breeds (which are in fact closely related) are known for their intelligence, responsiveness to obedience, and early maturation. There is also a recent trend of breeding a Labrador with a Poodle, to create a new hypoallergenic breed called a Labradoodle that is more suitable for those who suffer allergies.

Guide dog training

Guide dog puppies generally leave the breeding facility at about 8-10 weeks of age, where they go to 'puppy raisers' or 'puppy walkers.' These are families that volunteer to give training and basic items to a potential guide dog for up to 16 months, during which time the raisers or walkers expose the puppy to as many real-world experiences as possible. At the end of the 16-month period, the puppy is brought back to the guide dogs school. At this point, some of the schools conduct a test to analyze the dog's potential for guide dog work. If the dog passes this test, they continue on to harness training. At the end of approximately 2-3 months of individual training, blind students are brought to the school to work with the instructors and get a guide dog. After an additional 3 months, the team is ready to go out and be on their own.

Guide dog training schools

- [http://www.seeingeye.org/ The Seeing Eye] (Morristown, New Jersey)
- [http://www.guidedogsofamerica.org/ The Guide Dogs of America] (Sylmar, California
- [http://www.guidedogs.com Guide Dogs for the Blind] (San Rafael, California)
- [http://www.guidedog.org/ Guide Dog Foundation for the Blind Inc.] (Smithtown, New York

Assistance dog

An assistance dog is a dog that is specially trained to help a person with a disability. According to Assistance Dogs International, "The three types of Assistance Dogs are guide dogs for the blind and the visually impaired, hearing dogs for the deaf and hard of hearing and service dogs for people with disabilities other than those related to vision or hearing."

External links

- [http://www.guidedogsofamerica.org/ The Guide Dogs of America]
- [http://www.usdoj.gov/crt/ada/qasrvc.htm Legal information about service dogs in the U.S.]
- [http://www.deltasociety.org The Delta Society]
- [http://www.workingdogs.com Working Dogs Cyberzine]
- [http://www.adionline.org Assistance Dogs International]
- [http://www.iaadp.org International Association of Assistance Dog Partners]
- [http://www.doggroups.com/community/viewforum.php?f=144 Assistance Dog Discussions]
- [http://dogswithjobs.com/about_dogs/dog_jobs/assistance_dogs.html Assistance Dogs - Dogs in Human Health]
- [http://www.dogguides.com/programs/programs.htm Lions Foundation of Canada Dog Guides]
- [http://www.cci.org Canine Companions for Independence] Category:Assistance dogs

Visually impaired

Visual impairment is the functional loss of vision. According to the [http://www.nichcy.org/ National Dissemination Center for Children with Disabilities], "the terms partially sighted, low vision, legally blind, and totally blind are used in the educational context to describe students with visual impairments. They are defined as follows: #Partially sighted indicates some type of visual problem has resulted in a need for special education; #Low vision generally refers to a severe visual impairment, not necessarily limited to distance vision. Low vision applies to all individuals with sight who are unable to read the newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses. They use a combination of vision and other senses to learn, although they may require adaptations in lighting or the size of print, and, sometimes, braille; #Legally blind indicates that a person has less than 20/200 vision in the better eye or a very limited field of vision (20 degrees at its widest point); and #Totally blind students learn via braille or other non-visual media. Visual impairment is the consequence of a functional loss of vision, rather than the eye disorder itself. Eye disorders which can lead to visual impairments can include retinal degeneration, albinism, cataracts, glaucoma, muscular problems that result in visual disturbances, corneal disorders, diabetic retinopathy, congenital disorders, and infection."

External links

- [http://www.viguide.com/ Information on many topics pertaining to parenting and teaching a child with visual impairments]
- [http://www.migraine-aura.org/EN/Visual_Symptoms.html Visual impairment during migraine] Category:Disability

Foster home

Foster care is a system by which adults care for minor children who are not able to live with their biological parents. In the United States, many states have provisions for voluntary or involuntary foster care. Voluntary foster care may be in circumstances where a parent is unable or unwilling to care for a child. For instance, a child may have behavioral problems requiring specialized treatment. Involuntary foster care may be necessary in situations involving child abuse or neglect. Some children in foster care are awaiting adoption, while others are temporarily placed there, for example if a single parent is in prison. Requirements to be a foster parent vary by jurisdiction, as do monetary reimbursement and other benefits which they receive. In some states, foster parents may be single or a couple, younger or older adults, with or without biological children in their home. Often, "empty nesters" whose children have grown up and left the home may choose to take in foster children. Foster care is intended to be a temporary living situation for children. The goal of foster care is to reunify with their parent or guardian or find another suitable permanent living arrangement. This may include an adoptive home, guardianship, or placement with a relative. At times, the bond that develops during foster care will lead to the foster parents adopting the child. In some instances, children may be placed in a long-term foster placement. For older adolescents, a foster care program may offer education and resources to prepare for a transition to independent living.

Foster homes in the United States

In the United States, foster home licensing requirements vary from state to state but are generally overseen by the state's Department of Social Services. In many states children unable to function in a foster home, usually due to behavioral problems stemming from child abuse and neglect, are placed in Residential Treatment Facilities (RTFs) or other such group homes meant to treat children with similar backgrounds. The focus of treatment in such facilities is to prepare the child for a return to a foster home, to an adoptive home, or to the biological parents when applicable.

Recent United States Foster Care Legislation

On November 19, 1997, President Bill Clinton signed a new foster care law (The Adoption and Safe Families Act 1997, [http://www.acf.dhhs.gov/programs/cb/laws_policies/policy/pi/pi9802.htm]) which dramatically reduced the time children are allowed to remain in foster care before being available for adoption. The new law requires state child welfare agencies to identify cases where "aggravated circumstances" make permanent separation of child from biological family the best option for the safety and well-being of the child.

External links

- [http://web.ncf.ca/fe281/radio.html Too many stops] Audio documentary documenting former foster child's life story. Aired on CBC Radio Outfront on September 12, 2002.
- [http://www.adoptioninformation.com/ Adoptioninformation.com] - Wiki-style site for everything adoption and foster.
- [http://www.fosterparenting.com/ FosterParenting.com] Extensive resource about foster parenting and foster care
- [http://www.fostercares.org/ FosterCares.org] Non-profit organization providing free clothing, toys, and equipment to foster children throughout the state of Georgia.
- [http://www.abchome.org/ Alabama Baptist Childrens Home] Baptist agency that provides private and public foster care Category:Family
- [http://www.pbs.org/wnet/agingout/index-hi.html Aging Out] Aging Out is a documentary produced by PBS that chronicles the obstacles faced by teens who 'age out' of the foster care system.
- [http://www.fccy.org Foster Care] of Family Care for Children and Youth. A private, nonprofit social service agency providing children with specialized, community-based foster care services.

Obedience training

Obedience training involves training an animal, most often a dog, to obey basic control commands such as sit, down, and heel. There are almost as many methods of training as there are trainers, but over time the basic strategy has shifted away from punishment or avoidance training (negative reinforcement) to positive reinforcement, where the dog is rewarded for doing the correct thing during most phases of training rather than being punished for not doing what the trainer wants.

History

Working dogs have always learned to obey commands related to the work that they historically performed, such as when a sheepdog moves a flock of animals in response to a shepherd's whistled directions, or a hunting dog searching for (or chasing down) quarry or leaving the treed quarry at the hunter's command. It has been only in more modern times, as the dog has become more of a companion than a hired servant (paid in food and a dry place to lie down) who lived in the barn with other livestock, that obedience training has become a separate and specific skill (for both the owner and the dog). In the twentieth century, formalized dog training originated in military and police applications, and many theories on how to train a dog came out of the same mentality that created boot camp for soldiers. In the middle and late part of the century, however, more research into operant conditioning and positive reinforcement occurred as wild animal shows became more popular-- Traditional methods of teaching animals behavior (as with dogs) proved irrelevant when, for example, a trainer had to instruct a dolphin or an orca. These aquatic mammal trainers used clickers (a small box that makes a loud click when pushed on) to "mark" desired behavior, giving food as a reward. The improvements in training methods spread gradually into the world of dog training. Every decade sees new methods and new attitudes reach mainstream training classes.

Companion obedience

There are at least three levels of obedience training:
- Basic behavior
- Training for interaction with the community at large
- Competitive obedience At a basic level, owners want dogs with whom they can pleasantly share a house, a car, or a walk in the park. Some dogs need only a minimum amount of training to learn to eliminate outside (be housebroken), to sit, to lie down, or to come on command (obey a recall). Many other dogs prove more challenging. New dog owners might find training difficult because they expect dogs to think and act like humans, and are surprised and baffled when the dogs don't (or they fail to make progress because they fail to realize that the dogs don't). Dogs who demonstrate the previously mentioned basic skills, as well as walking reasonably well on a leash and a few other minor tasks, can be tested for and earn the American Kennel Club's (AKC) Canine Good Citizen title.

Competitive obedience

For dog owners who enjoy competition and relish the opportunity to work as a highly tuned team with their dogs, competitive obedience is available. In competition, merely sitting, lying down, or walking on a leash are insufficient. The dog and handler must perform the activities off leash and in a highly stylized and carefully defined manner. For example, on a recall, the dog must come directly to the handler, without sniffing or veering to one side, and sit straight in front of the handler, not at an angle or off to one side or the other.

Competition obedience exercises

Canine Good Citizen A handler can choose her own commands, but the actions that the dog must perform are well defined. As a dog progresses from novice to advanced competition, the requirements become more challenging and the list of actions that he must perform becomes longer. Exercises in AKC competition are offered at three levels: Novice, Open (intermediate), and Utility (advanced); a dog must complete the requirements at each level before moving on the next. AKC exercises are:
- Recall (Come) :The handler leaves the dog in a sitting position at one side of the ring, walks to the opposite side, and turns to face the dog. On the judge's command, the handler calls or signals the dog to come. The dog must come directly to the handler at a brisk trot or gallop, and sit squarely in front, close enough that the handler can touch the dog's head without bending or stretching, but not between the handler's feet. On the judge's order, the handler commands or signals the dog to "finish". The dog must go briskly to heel position and sit squarely at heel.
- Drop on Recall (Open class) :The handler leaves the dog as in the Recall exercise. On the judge's command, the handler calls or signals the dog to come. The dog must come directly to the handler at a brisk trot or gallop. While the dog is coming in, the judge signals, and the handler commands or signals the dog to drop (lie down). The dog must immediately assume a completely down position. The dog must hold the position until commanded or signaled to come, then complete the exercise as in the Recall.
- Heel :Following commands of the judge, the dog and handler team walks a predetermined pattern that must include at least one left, one right, and one about turn, as well as a fast and a slow section, and at least one halt. During this entire exercise, the dog must maintain heel position, and sit quickly at heel whenever the handler stops. This exercise is performed twice in Novice class (once on lead and once off-lead), once in Open class, and once in the Utility class, as part of the Signal exercise.
- Sit :Sit is not an obedience exercise, but is a part of almost all of the other exercises. The dog must sit without any command (called an automatic sit) whenever the handler stops, and at the end of most of the exercises.
- Long Sit and Long Down (Novice and Open Classes) :These exercises are performed by groups of dogs in the ring at the same time. For the Novice Long Sit, the handlers command and/or signal their dogs to sit, then to stay. The handlers walk across the ring and stand facing their dogs. The dog must maintain the sit position without moving from its position, barking, or whining. After one minute, the judge orders the handlers to return, and they return to heel position by walking around their dogs. For the Novice Long Down, the handlers command and/or signal their dogs to down, and the dogs must assume the down position without assistance. The handlers command and/or signal their dogs to stay, and proceed as in the Long Sit, except that the judge waits three minutes before ordering them to return. :The Open Long Sit and Long Down are done in the same manner, except that the handlers leave the ring in a single file and go completely out of the dogs' sight. They remain out of sight for three minutes for the Sit and five minutes for the Down.
- Retrieve on the Flat (Open class) :The handler stands with the dog sitting in heel position facing the open ring. On order from the judge, the handler commands and/or signals the dog to stay, then throws an approved dumbbell at least 20 feet. On the judge's order, the handler commands the dog to fetch. The dog must go straight to the dumbbell at a brisk trot or gallop, retrieve it, return directly to the handler, and sit in front as in the Novice Recall. The dog must not mouth or play with the dumbbell. Upon order from the judge, the handler gives the release command and takes the dumbbell. The judge then orders the handler to have the dog finish as in the Novice Recall.
- Retrieve Over High Jump (Open class) :This exercise is the same as the Retrieve on the flat, except that the handler starts by standing in front of a solid jump that is as high as the dog's shoulder height. The handler throws the dumbbell over the jump. The dog must jump over the jump, retrieve the dumbbell, and return by jumping over the jump again. The remainder of the exercise is the same as the Retrieve on the Flat.
- Scent discrimination (Utility class) :The handler presents the judge with an approved set of 5 numbered metal and 5 numbered leather articles. The judge selects one of each, placing them where the handler can reach them, and arranges the rest on the floor or ground approximately 20 feet from the handler, being certain to touch each article. At this point, the dog and handler turn so they are facing away from the articles, and the handler uses his hands to scent one of the selected articles. The judge takes the scented article without touching it, and places it with the other articles. On the judge's command the handler turns and sends the dog. The dog must go directly to the articles at a brisk trot or gallop, select the article that was scented by the handler, and retrieve it as in the Open Retrieve on the Flat. The exercise is then repeated using the other selected article. heel position For example, in the scent article exercise, the dog searches for a dumbbell that has been scented by the handler and placed within a pile of identical metal and leather dumbbells by an assistant. The dog must find the correct article based only on its unique scent and retrieve it. Dogs can earn obedience titles including an obedience championship. For example, the American Kennel Club (AKC) awards an "Obedience Trial Championship" (OTCh) to the dog-and-handler team that defeats a large number of other teams in open competition. In the United States, a purebred dog recognized by the AKC can compete under AKC rules; dogs not recognized by the AKC can earn titles in the United Kennel Club (UKC), Mixed Breed Dog Club of America (MBDCA), American Mixed Breed Obedience Registry (AMBOR), or Australian Shepherd Club of America (ASCA). Contrary to what one might expect, an obedience champion might not have excellent companion obedience skills; the actions are so highly formalized for performance in the obedience ring that they do not automatically translate to a dog who walks pleasantly on a leash, comes when called in the back yard, or keeps his nose off the dinner table.

Obedience for Other Purposes

There are many reasons for training dogs beyond the level required for basic companionship. For example, service dogs must obey their sit and down commands perfectly at all times, but they do not have to conform to the rigid rules of competitive obedience. Dogs competing in dog sports, such as flyball, agility or Schutzhund, must be trusted in an open field, off leash and surrounded by other people, dogs, hamburgers, and frisbees. This requires more focused attention on the owner and a better recall than that found in most household companion dogs, but again it can be a different kind of training than that required for formal obedience.

Dog Intelligence and Training

Certain breeds, such as Border Collies and Golden Retrievers, are easier to train than others, such as some hounds and sled dogs. Still, the Border Collie's high energy level can lead it to unwanted behavior if its exercise and mental needs are not met, whereas the Golden Retriever can be somewhat more relaxed. Dog intelligence is exhibited in many different ways, and a dog who might not be easy to train might none-the-less be quite adept at figuring out how to open kitchen cabinets or to escape from the yard. Novice dog owners need to consider a dog's trainability as well as its energy level, exercise requirements, and other factors before choosing a new pet. No breed is impossible to obedience train, but novice owners might find that training some breeds is quite difficult. The capacity to learn basic obedience—and even complicated behavior—is inherent in all dogs. Owners must simply be more patient, or creative, or both, with some breeds than with others.

References

- [http://www.akc.org/rules/obedience.cfm AKC obedience regulations]

External links

- [http://www.pupforum.com/findatrainer/ Find a Dog Trainer]
- [http://www.dog-play.com/obedience.html Dog-Play Obedience Page]
- [http://www.dogpatch.org/obed/ The Dog Obedience and Training Page] =Sanctioning Organizations= Organizations offering obedience titles in the United States:
- [http://www.amborusa.org/ AMBOR]
- [http://www.ukcdogs.com/ United Kennel Club]
- [http://www.akc.org/events/obedience/index.cfm AKC Obedience]
- [http://www.asca.org/Programs/Obedience/index.htm ASCA Obedience]
- [http://mbdca.tripod.com/ Mixed Breed Dog Club] Category:Dog training and behavior

Color blind

Color blindness, or color vision deficiency, in humans is the inability to perceive differences between some or all colors that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain chemicals. The English chemist John Dalton in 1794 published the first scientific paper on the subject, "Extraordinary facts relating to the vision of colors", after the realization of his own color blindness; because of Dalton's work, the condition is sometimes called Daltonism, although this term is now used for a type of color blindness called deuteranopia (see below). Color blindness is usually classed as a disability; however, in select situations color blind people have advantages over people with normal color vision. Color blind hunters are better at picking out prey against a confusing background, and the military have found that color blind soldiers can sometimes see through camouflage that fools everyone else. Monochromats may have a minor advantage in dark vision, but only in the first five minutes of dark adaptation. Monochromats

Prevalence

Color blindness affects a significant number of people, although exact proportions vary among groups. In Australia, for example, approximately 4% of the population suffers from some deficiency in color perception. Isolated communities with a restricted gene pool sometimes produce high proportions of color blindness, including the less usual types. Examples include rural Finland and some of the Scottish islands. Scottish

Causes of color blindness

There are many types of color blindness. The most common varieties are hereditary (genetic) photoreceptor disorders, but it is also possible to acquire color blindness through damage to the retina, optic nerve, or higher brain areas. Higher brain areas implicated in color processing include the parvocellular pathway of the lateral geniculate nucleus of the thalamus, and visual area V4 of the visual cortex. Acquired color blindness is generally unlike the more typical genetic disorders. For example, it is possible to acquire color blindness only in a portion of the visual field but maintain normal color vision elsewhere. Some forms of acquired color blindness are reversible. Transient color blindness also occurs (very rarely) in the aura of some migraine sufferers. migraine migraine

Classification of color deficiencies

- Acquired
- Congenital :
- Dichromacy ::
- Protanopia ::
- Deuteranopia ::
- Tritanopia :
- Anomalous trichromacy ::
- Protanomaly ::
- Deuteranomaly ::
- Tritanomaly :
- Monochromacy ::
- Rod monochromacy ::
- Achromatopsia The normal human retina contains two kinds of light sensitive cells: the rod cells (active in low light) and the cone cells (active in normal daylight). Normally, there are three kinds of cones, each containing a different pigment. The cones are activated when the pigments absorb light. The absorption spectra of the pigments differ; one is maximally sensitive to short wavelengths, one to medium wavelengths, and the third to long wavelengths (their peak sensitivities are in the blue, yellowish-green, and yellow regions of the spectrum, respectively). It is important to realize that the absorption spectra of all three systems cover much of the visible spectrum, so it is incorrect to refer to them as "blue", "green" and "red" receptors, especially because the "red" receptor actually has its peak sensitivity in the yellow. The sensitivity of normal color vision actually depends on the overlap between the absorption spectra of the three systems: different colors are recognized when the different types of cone are stimulated to different extents. For example, red light stimulates the long wavelength cones much more than either of the others, but the gradual change in hue seen as wavelength reduces is the result of the other two cone systems being increasingly stimulated as well. The different kinds of color blindness result from one or more of the different cone systems either not functioning at all, or functioning in an unusual way. When one cone system is compromised, dichromacy results. The most frequent forms of human color blindness result from problems with either the middle or long wavelength sensitive cone systems, and involve difficulties in discriminating reds, yellows, and greens from one another. They are collectively referred to as "red-green color blindness", though the term is an over-simplification and somewhat misleading. Other forms of color blindness are much rarer. They include problems in discriminating blues from yellows, and the rarest forms of all, complete color blindness or monochromacy, where one cannot distinguish any color from grey, as in a black-and-white movie or photograph.

Red-green color blindness

Types of red-green color blindness

There are several types of red-green color blindness:
- Protanopia: Lacking the long-wavelength sensitive retinal cones, those with this condition are unable to distinguish between colors in the green-yellow-red section of the spectrum. They have a neutral point at a wavelength of 492 nm—that is, they cannot discriminate light of this wavelength from white. Their sensitivity to light in the orange and red part of the spectrum is also reduced. Very few people have been found who have one normal eye and one protanopic eye. These unilateral dichromats report that with only their protanopic eye open, they see wavelengths below the neutral point as blue and those above it as yellow. This is a rare form of color blindness.
- Deuteranopia: Lacking the medium-wavelength cones, those affected are again unable to distinguish between colors in the green-yellow-red section of the spectrum. Their neutral point is at a slightly longer wavelength, 498 nm. This is one of the rarer forms of colorblindness making up about 1% of the male population, also known as Daltonism after Dalton. (Dalton's diagnosis was confirmed as deuteranopia in 1995, some 150 years after his death, by DNA analysis of his preserved eyeball.) Deuteranopic unilateral dichromats report that with only their deuteranopic eye open, they see wavelengths below the neutral point as blue and those above it as yellow.
- Protanomaly: Having a mutated form of the long-wavelength pigment, whose peak sensitivity is at a shorter wavelength than in the normal retina, protanomalous individuals are less sensitive to red light than normal. This means that they are less able to discriminate colors, and they do not see mixed lights as having the same colors as normal observers. They also suffer from a darkening of the red end of the spectrum. This causes reds to reduce in intensity to the point where they can be mistaken for black. Protanomaly is a fairly rare form of color blindness, making up about 1% of the male population.
- Deuteranomaly: Having a mutated form of the medium-wavelength pigment. The medium-wavelength pigment is shifted towards the red end of the spectrum resulting in a reduction in sensitivity to the green area of the spectrum. Unlike protanomaly the intensity of colors is unchanged. This is the most common form of color blindness, making up about 6% of the male population.

Dichromacy and anomalous trichromacy

Protanopes and deuteranopes are dichromats; that is, they can match any color they see with some mixture of just two spectral lights (whereas normally humans are trichromats and require three lights). Those having protanomaly or deuteranomaly are trichromats, but the color matches they make differ from the normal: In order to match a given spectral yellow light, protanomalous observers need more red light in a red/green mixture than a normal observer, and deuteranomalous observers need more green. They are called anomalous trichromats. Protanomaly and deuteranomaly can be readily observed using an instrument called an anomaloscope, which mixes spectral red and green lights in variable proportions, for comparison with a fixed spectral yellow. If this is done in front of a large audience of men, as the proportion of red is increased from a low value, first a small proportion of people will declare a match, while most of the audience are seeing the mixed light as greenish. These are the deuteranomalous observers. Next, as more red is added the majority will say that a match has been achieved. Finally, as yet more red is added, the remaining, protanomalous, observers will declare a match at a point were everyone else is seeing the mixed light as definitely reddish.

Genetics of red-green color blindness

Genetic red-green color blindness affects men much more often than women, because the genes for the red and green color receptors are located on the X chromosome, of which men have only one and women have two. Such a trait is called sex-linked. Genetic females (46, XX) are red-green color blind only if both their X chromosomes are defective with a similar deficiency, whereas genetic males (46, XY) are color blind if their only X chromosome is defective. The gene for red-green color blindness is transmitted from a color blind male to all his daughters who are heterozygote carriers and are perceptually unaffected. In turn, a carrier woman passes on a mutated X chromosome region to only half her male offspring. The sons of an affected male will not inherit the trait, since they receive his Y chromosome and not his (defective) X chromosome. Because one X chromosome is inactivated at random in each cell during a woman's development, it is possible for her to have four different cone types, if, for example, a carrier of protanomaly has a child with a deuteranomalic man. The deficiencies can combine to form a fourth receptor whose absorption spectrum peaks in the yellow-green area. Denoting the normal vision alleles by P and D and the anomalous by p and d, the carrier is PD pD and the man is Pd. The daughter is either PD Pd or pD Pd. Suppose she is pD Pd. The cells in her body express her mother's chromosome pD and her father's Pd. Thus some of the cones are anomalous with both deficiencies and some are normal. As a result she has the normal short, medium and long wavelength-sensitive types of cone, with an additional category of receptor that combines the deficiencies. Such women are tetrachromats, since with their four-cone systems, they require a mixture of four spectral lights to match an arbitrary light!

Blue-yellow color blindness

Color blindness involving the inactivation of the short-wavelength sensitive cone system (whose absorption spectrum peaks in the bluish-violet) is called tritanopia or, loosely, blue-yellow color blindness. Mutation of the short-wavelength sensitive cones is called tritanomaly. Tritanopia is equally distributed among males and females, because the gene coding for the short-wavelength receptor is located on chromosome 7 and therefore not sex-linked, but since mutations in both copies are required, it is less frequently apparent.

Monochromacy

Complete inability to distinguish any colors is called monochromacy. It occurs in three forms: # cone monochromacy, where only a single cone system appears to be functioning, so that no colors can be distinguished, but vision is otherwise more or less normal. # achromatopsia or rod monochromacy, where the retina contains no cone cells, so that in addition to the absence of color discrimination, vision in lights of normal intensity is difficult. While normally rare, achromatopsia is very common on the island of Pingelap, a part of the Pohnpei state, where it is called maskun: about 1/12 of the population there has it. The island was devastated by a storm in the eighteenth century, and one of the few male survivors carried a gene for achromatopsia; the population is now several thousand, of whom about 30% carry this gene. # Color agnosia or "central achromatopsia", where the person can not perceive colors, even though the eyes are capable of distinguishing them. Some sources do not consider this to be true color blindness, because the failure is of perception, not of vision. It is a form of visual agnosia.

Diagnosis

The Ishihara color test, which consists of a series of pictures of colored spots, is the test most often used to diagnose red-green color deficiencies. A figure (usually one or more Arabic digits) is embedded in the picture as a number of spots in a slightly different color, and can be seen with normal color vision, but not with a particular color defect. The full set of tests has a variety of figure/background color combinations, and enable diagnosis of which particular visual defect is present. The anomaloscope, described above, is also used in diagnosing anomalous trichromacy. However, the Ishihara color test is criticized for containing only numerals and thus not being useful for young children, who have not yet learned to use numerals. It is often stated that it is important to identify these problems as soon as possible and explain them to the children to prevent possible problems and psychological traumas. For this reason, alternative color vision tests were developed using only symbols (square, circle, car). Most clinical tests are designed to be fast, simple, and effective at identifying broad categories of color blindness. In academic studies of color blindness, on the other hand, there is more interest in developing flexible tests ([http://www.hubmed.org/display.cgi?uids=15192692], for example) to collect thorough datasets, identify copunctal points, and measure just noticeable differences.

Simple test for color blindness

To the right are four pictures with 2-digit numbers designed to test for different kinds of color blindness. Note that monitor or lighting differences may affect whether or not the images can be seen.

Treatment and management

There is generally no treatment to cure color deficiencies, however, certain types of tinted filters and contact lenses may help an individual to distinguish different colors better.

Design implications of color blindness

Color codes present particular problems for color blind people as they are often difficult or impossible for color blind people to understand. Good graphic design avoids using color coding or color contrasts alone to express information, as this not only helps color blind people, but also aids understanding by normally sighted people. The use of Cascading Style Sheets on the world wide web allows pages to be given an alternative color scheme for color-blind readers. [http://wellstyled.com/tools/colorscheme2/index-en.html This color scheme generator] helps a graphic designer see color schemes as seen by eight types of color blindness. It is sometimes claimed that in extreme emergencies everyone is color blind. When the need to process visual information as rapidly as possible arises, for example in a train or aircraft crash, the visual system may operate only in shades of grey, with the extra information load in adding color being dropped. This is an important possibility to consider when designing, for example, emergency brake handles or emergency phones.

Misconceptions & Compensations

Color blindness is not the swapping of colors in the observer's eyes. Grass is never red, stop signs never green. Distinguishing a Granny Smith from a Braeburn is not a problem. The color impaired do not learn to call red "green" and vice versa. Most color blind persons have learned their vulnerabilities and are acutely aware of just which colors will be confused. In some cases this can lead to an acute color sensitivity due to the fact that nuance of color will need to be categorized more clearly. A person who has limited ability to distinguish brown from red or green may become more concerned as to the shade of taupe or olive of a specific material than a person who's normal vision allows them to see exactly which shade of greenish-brown they are looking at. The United State Military has found that color blind individuals can be more easily trained as snipers due to the fact that they are more acutely aware of differences in texture and pattern and thereby less likely to be fooled by camouflage patterns.

External links

- [http://psychology.ucalgary.ca/pace/VA-Lab/colourperceptionweb/congenital.htm Congenital Colour Vision Deficiencies], description from the University of Calgary
- [http://colorvisiontesting.com/online%20test.htm Color Vision Testing Made Easy], samples of this alternative test
- Attempts to simulate some rough features of color blind vision:
- [http://webexhibits.org/causesofcolor/2.html How do things look to colorblind people?], Causes of Color -- WebExhibits
- [http://colorvisiontesting.com/what%20colorblind%20people%20see.htm How the world looks to a color blind person], example images drawn using distorted colors
- [http://www.vischeck.com/ VisCheck], demonstrations of color blindness and simulation software
- [http://colorfilter.wickline.org/ ColorBlind Web Page Filter], shows how your web page looks under various forms of color blindness
- [http://www.etre.com/tools/colourcheck/ Etre Colour Check], determine the colour difference and contrast between any two colours used on your site
- [http://www.etre.com/tools/colourblindsimulator/ Etre Colour Blindness Simulator], upload your images and see how they look to a colour blind person Category:Color Category:Vision ja:色覚異常

Color

Color or colour is the perception of the frequency (or wavelength) of light, and can be compared to how pitch (or a musical note) is the perception of the frequency or wavelength of sound. It is a perception which in humans derives from the ability of the fine structures of the eye to distinguish (usually three) differently filtered analyses of a view. The perception of color is influenced by biology (some people are born seeing colors differently or not at all; see color blindness), long-term history of the observer, and also by short-term effects such as the colors nearby. (This is the basis of many optical illusions.) The science of color is sometimes called chromatics. It includes the perception of color by the human eye, the origin of color in materials, color theory in art, and the physics of color in the electromagnetic spectrum.

Physics of color

The colors of the visible light spectrum.

color	wavelength interval	frequency interval
red	~ 625-740 nm	~ 480-405 THz
orange	~ 590-625 nm	~ 510-480 THz
yellow	~ 565-590 nm	~ 530-510 THz
green	~ 500-565 nm	~ 600-530 THz
cyan	~ 485-500 nm	~ 620-600 THz
blue	~ 440-485 nm	~ 680-620 THz
violet	~ 380-440 nm	~ 790-680 THz
Continuous optical spectrum Image:Spectrum441pxWithnm.png Designed for monitors with gamma 1.5.
Computer "spectrum" Image:Computerspectrum.png The bars below show the relative intensities of the three colors mixed to make the color immediately above.

Color, frequency, and energy of light.

Color	$\lambda \,\!$ /nm	$\nu \,\!$ /10¹⁴ Hz	$\nu_b \,\!$ /10⁴ cm^-1	$E \,\!$ /eV	$E \,\!$ /kJ mol^-1
Infrared	>1000	<3.00	<1.00	<1.24	<120
Red	700	4.28	1.43	1.77	171
Orange	620	4.84	1.61	2.00	193
Yellow	580	5.17	1.72	2.14	206
Green	530	5.66	1.89	2.34	226
Blue	470	6.38	2.13	2.64	254
Violet	420	7.14	2.38	2.95	285
Near ultraviolet	300	10.0	3.33	4.15	400
Far ultraviolet	<200	>15.0	>5.00	>6.20	>598

Electromagnetic radiation is a mixture of radiation of different wavelengths and intensities. When this radiation has a wavelength inside the human visibility range (approximately from 380 nm to 740 nm), it is known as light within the (human) visible spectrum. The light's spectrum records each wavelength's intensity. The full spectrum of the incoming radiation from an object determines the visual appearance of that object, including its perceived color. As we will see, there are many more spectra than color sensations; in fact one may formally define a color to be the whole class of spectra which give rise to the same color sensation, although any such definition would vary widely among different species and also somewhat among individuals intraspecifically. A surface that diffusely reflects all wavelengths equally is perceived as white, while a dull black surface absorbs all wavelengths and does not reflect (for mirror reflection this is different: a proper mirror also reflects all wavelengths equally, but is not perceived as white, while shiny black objects do reflect). The familiar colors of the rainbow in the spectrum—named from the Latin word for appearance or apparition by Isaac Newton in 1671—contains all those colors that consist of visible light of a single wavelength only, the pure spectral or monochromatic colors. The frequencies are approximations and given in terahertz (THz). The wavelengths, valid in vacuum, are given in nanometers (nm). A list of other objects of similar size is available.

Important note

The color table should not be interpreted as a definite list – the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors is a matter of taste and culture. Similarly, the intensity of a spectral color may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive-green.

Spectral versus non-spectral colors

Most light sources are not pure spectral sources; rather they are created from mixtures of various wavelengths and intensities of light. To the human eye, however, there is a wide class of mixed-spectrum light that is perceived the same as a pure spectral color. In the table above, for instance, when your computer screen is displaying the "orange" patch, it is not emitting pure light at a fixed wavelength of around 600 nm (which is something most computer screens are unable to do). Rather, it is emitting a mixture of about two parts red to one part green light. Were you to print this page on a color printer, the orange patch on the paper, when lit with white light, would reflect yet another, more continuous spectrum. We cannot see those differences (although many animals can), and the reason has to do with the pigments that make up our color vision cells (see below). A useful quantification of this property is the dominant wavelength, which matches a wavelength of spectral light to a non-spectral source that evokes the same color perception. Dominant wavelength is the formal background for the popular concept of hue. In addition to the many light sources that can appear to be pure spectral colors but are actually mixtures, there are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (which are a mixture of red and violet light, from either end of the spectrum). Some examples of necessarily non-spectral colors are the achromatic colors (black, gray and white) and other colors such as pink, tan and magenta. See metamerism (color) for a basic introduction as to why color matching challenges exist.

Physical basis of color

A light wave can be analyzed as a superposition of sine waves, each of which has a specific frequency and wavelength. The eye gives limited information about the relative intensities of these sine waves (but not their phases — the eye is even more blind to phase than the ear, which can detect phase relationships of sounds only in certain very specific contexts). To understand which particular color perception will arise from a particular physical spectrum requires knowledge of the physiology of the retina. The human eye is also insensitive to polarization in most cases (though see Haidinger's brush), whereas some fish and mollusks can perceive it.

Color vision

Though the exact status of color is a matter of current philosophical dispute, color is arguably a psychophysical phenomenon that exists only in our minds. (See Qualia, for some of that dispute.) A "red" apple does not give off "red light", and it is misleading to think of things that we see, or of light itself, as objectively colored at all. Rather, the apple simply absorbs light of various wavelengths shining on it to different degrees, in such a way that the unabsorbed light which it reflects is perceived as red. An apple is perceived to be red only because normal human color vision perceives light with different mixes of wavelengths differently—and we have language to describe that difference. language In 1931, an international group of experts called the Commission Internationale d'Eclairage (CIE) developed a mathematical color model. The premise used by the CIE is that color is the combination of three things: a light source, an object, and an observer. The CIE tightly controlled each of these variables in an experiment that produced the measurements for the system. Although Aristotle and other ancient scientists speculated on the nature of light and color vision, it was not until Newton that light was correctly identified as the source of the color sensation. Goethe studied the theory of colors, and in 1801 Thomas Young proposed his trichromatic theory which was later refined by Hermann von Helmholtz. That theory was confirmed in the 1960s and will be described below. Hermann von Helmholtz The retina of the human eye contains three different types of color receptor cells, or cones. One type, relatively distinct from the other two, is most responsive to light that we perceive as violet, with wavelengths around 420 nm (cones of this type are sometimes called short-wavelength cones, S cones, or, most commonly but quite misleadingly, blue cones). The other two types are closely related genetically, chemically and in response. Each type is most responsive to light that we perceive as green or greenish. One of these types (sometimes called long-wavelength cones, L cones, or, misleadingly, red cones) is most sensitive to light we perceive as yellowish-green, with wavelengths around 564 nm; the other type (sometimes called middle-wavelength cones, M cones, or misleadingly green cones) is most sensitive to light perceived as green, with wavelengths around 534 nm. The term "red cones" for the long-wavelength cones is deprecated as this type is actually maximally responsive to light we perceive as greenish, albeit longer wavelength light than that which maximally excites the mid-wavelength/"green" cones. The sensitivity curves of the cones are roughly bell-shaped, and overlap considerably. The incoming signal spectrum is thus reduced by the eye to three values, sometimes called tristimulus values, representing the intensity of the response of each of the cone types. Because of the overlap between the sensitivity ranges, some combinations of responses in the three types of cone are impossible no matter what light stimulation is used. For example, it is not possible to stimulate only the mid-wavelength/"green" cones: the other cones must be stimulated to some degree at the same time, even if light of some single wavelength is used (including that to which the target cones are maximally sensitive). The set of all possible tristimulus values determines the human color space. It has been estimated that humans can distinguish roughly 10 million different colors, although the identification of a specific color is highly subjective, since even the two eyes of a single individual perceive colors slightly differently. This is discussed in more detail below. The rod system (which vision in very low light relies on exclusively) does not by itself sense differences in wavelength; therefore it is not normally implicated in color vision. But experiments have conclusively shown that in certain marginal conditions a combination of rod stimulation and cone stimulation can result in color discriminations not based on the mechanisms described above. While the mechanisms of color vision at the level of the cones in the retina are well described in terms of tristimulus values (see above), color processing and perception above that base level are organized differently. A dominant theory of the higher neural mechanisms of color vision proposes three opponent processes, or opponent channels, constructed out of the raw input from the cones: a red-green channel, a blue-yellow channel, and a black-white ("luminance") channel. This theory tries to account for the structure of our subjective color experience (see discussion below). Blue and yellow are considered complementary colors, or opposites: you could not experience a bluish yellow (or a greenish red), any more than you could experience a dark brightness or a hot coldness. The four "polar" colors proposed as extremes in the two opponent processes other than black-white have some natural claim to being called primary colors. This is in competition with various sets of three primary colors proposed as "generators" of all normal human color experience (see below).

Clinical issues

If one or more types of a person's color-sensing cones are missing or less responsive than normal to incoming light, that person has a smaller or skewed color space and is said to be color deficient. Another term frequently used is color blind, although this can be misleading; only a small fraction of color deficient individuals actually see completely in black and white, and most simply have anomalous color perception. Some kinds of color deficiency are caused by anomalies in the number or nature of cones of the various types, as just described. Others (like central or cortical achromatopsia) are caused by neural anomalies in those parts of the brain where visual processing takes place. Some animals may have more than three different types of color receptor (most marsupials, birds, reptiles, and fish; see tetrachromat, below) or fewer (most mammals; these are called dichromats and monochromats). Humans and other old-world primates are actually rather unusual in possessing three kinds of receptors. An unusual and elusive neurological condition sometimes affecting color perception is synaesthesia.

Tetrachromat

A normal human is a trichromat (from Greek: tri=three, chroma=color). In theory it may be possible for a person to have four, rather than three, distinct types of cone cell. If these four types are sufficiently distinct in spectral sensitivity and the neural processing of the input from the four types is developed, a person may be a tetrachromat (tetra=four). Such a person might have an extra and slightly different copy of either the medium- or long-wave cones. It is not clear whether such people exist or that the human brain could actually process the information from such an extra cone type separately from the standard three. However, strong evidence suggests that such people do exist, they are all female by genetic imperative, and their brains gladly adapt to use the additional information. For many species, tetrachromacy is the normal case, although the cone cells of animal tetrachromats have a very different (more evenly-spaced) spectral sensitivity distribution than those of possible human tetrachromats.

Color perception

There is an interesting phenomenon which occurs when an artist uses a limited color palette: the eye tends to compensate by seeing any grey or neutral color as the color which is missing from the color wheel. E.g.: in a limited palette consisting of red, yellow, black, and white, a mixture of yellow and black will appear as a variety of green, a mixture of red and black will appear as a variety of purple, and pure grey will appear bluish. When the eye shifts attention after viewing a color for some time, then an afterimage of the complement of that color (the color opposite to it in the color wheel) is perceived by the eye for some time wherever it moves. This effect of color perception was utilised by Vincent van Gogh, a Post-Impressionist painter.

Effect of luminosity

Note that the color experience of a given light mixture may vary with absolute luminosity, because both rods and cones are active at once in the eye, with each having different color curves, and rods taking over gradually from cones as the brightness of the scene is reduced. This effect leads to a change in color rendition with absolute illumination levels that can be summarised in the "Kruithof curve".

Cultural influences

Different cultures have different terms for colors, and may also assign some color names to slightly different parts of the spectrum, or have a different color ontology: for instance, the Han character 青 (pronounced qīng in Mandarin and aoi in Japanese) has a meaning that covers both blue and green; blue and green are traditionally considered shades of 青; In more contemporary terms, they are 藍 (lán) and 綠 (lǜ) respectively. Similarly, languages are selective when deciding which hues are split into different colors on the basis of how light or dark they are. Apart from the black-grey-white continuum, English splits some hues into several distinct colors according to lightness: such as red and pink or orange and brown. To English speakers, these pairs of colors, which are objectively no more different that light green and dark green, are conceived as totally different. An Italian will make the same red-pink and orange-brown distinctions, but will also make a further distinction between blu and azzurro, which English speakers would simply call dark and light blue. To Italian speakers, blu and azzurro are as separate as red and pink or orange and brown. Color terms evolve. It is argued that there are a limited number of universal "basic color terms" which begin to be used by individual cultures in a relatively fixed order. For example, a culture would start with only two terms, meaning roughly 'dark' (covering black, dark colors and cold colors such as blue ) and 'bright' (covering white, light colors and warm colors such as red), before adding more specific color names, in the order of red; green and/or yellow; blue; brown; and orange, pink, purple, and/or gray. Older arguments for this theory also stipulated that the acquisition and use of basic color terms further along the evolutionary order indicated a more complex culture with more highly developed technology. A somewhat dated example of a universal color categories theory is Basic Color Terms: Their Universality and Evolution (1969) by Brent Berlin and Paul Kay. A more recent example of a linguistic determinism theory might be Is color categorisation universal? New evidence from a stone-age culture (1999) by Jules Davidoff et al. The idea of linguistically determined color categories is often used as evidence for the Sapir-Whorf hypothesis (Language, Thought, and Reality (1956) by Benjamin Lee Whorf). Additionally, different colors are often associated with different emotional states, values, or groups, but these associations can vary between cultures. In one system, red is considered to motivate action; orange and purple are related to spirituality; yellow cheers; green creates cosiness and warmth; blue relaxes; and white is associated with either purity or death. These associations are described more fully in the individual color pages, and under color psychology. See also: National colors

Color constancy

The trichromatric theory discussed above is strictly true only if the whole scene seen by the eye is of one and the same color, which of course is unrealistic. In reality, the brain compares the various colors in a scene, in order to eliminate the effects of the illumination. If a scene is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colors of the scene will nevertheless appear constant to us. This was discovered by Edwin Land in the 1970s and led to his retinex theory of color constancy.

Contrast

Note: the following comparison requires an all-digital display setup (commonly, a laptop or DVI-connected LCD) to avoid errors caused by an unfortunate interaction between frequency response and gamma curves. Compare the visibility of the RGB primary and secondary colors against a white background:

red

green

blue

red+green

green+blue

red+blue

red+green+blue

zero light

Again, compare variations on gray backgrounds—#7f7f7f, #5f5f5f & #9f9f9f—the eight RGB primaries are equidistant from #7f7f7f in a 3-d geometrical representation of RGB color space—a reminder of the importance of background color for color perception. Background = #7f7f7f

red

green

blue

red+green

green+blue

red+blue

red+green+blue

zero light

And let's look at black again, for completeness. (Note that your monitor background probably is not perfectly black, as you can see by switching off the monitor.) Background = #000000

red

green

blue

red+green

green+blue

red+blue

red+green+blue

zero light

Measurement and reproduction of color

monitor Two different light spectra which have the same effect on the three color receptors in the human eye will be perceived as the same color. This is exemplified by the white light that is emitted by fluorescent lamps, which typically has a spectrum consisting of a few narrow bands, while daylight has a continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although reflected colors from objects can look different. (This is often exploited e.g. to make fruit or tomatoes look more brightly red in shops.) Similarly, most human color perceptions can be generated by a mixture of three colors called primaries. This is used to reproduce color scenes in photography, printing, television, and other media. There are a number of methods or color spaces for specifying a color in terms of three particular primary colors. Each method has its advantages and disadvantages depending on the particular application. No mixture of colors, though, can produce a fully pure color perceived as completely identical to a spectral color, although one can get very close for the longer wavelengths, where the chromaticity diagram above has a nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green. Because of this, and because the primaries in color printing systems generally are not pure themselves, the colors reproduced are never perfectly saturated colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the gamut. The CIE chromaticity diagram can be used to describe the gamut. Another problem with color reproduction systems is connected with the acquisition devices, like cameras or scanners. The characteristics of the color sensors in the devices are often very far from the characteristics of the receptors in the human eye. In effect, acquisition of colors that have some special, often very "jagged", spectra caused for example by unusual lighting of the photographed scene can be relatively poor. Species that have color receptors different from humans, e. g. birds that may have four receptors, can differentiate some colors that look the same to a human. In such cases, a color reproduction system `tuned' to a human with normal color vision may give very inaccurate results for the other observers. The next problem is different color response of different devices. For color information stored and transferred in a digital form, color management technique based on color profiles attached to color data and to devices with different color response helps to avoid deformations of the reproduced colors. The technique works only for colors in gamut of the particular devices, e.g. it can still happen that your monitor is not able to show you real color of your goldfish even if your camera can receive and store the color information properly and vice versa.

Pigments and reflective media

When producing a color print or painting a surface, the applied paint changes the surface; if the surface is then illuminated with white light (which consists of equal intensities of all visible wavelengths), the reflected light will have a spectrum corresponding to the desired color. If a dab of paint looks red in white light, that is because the reflection of all non-red wavelengths is interrupted by the pigment, such that only red light is reflected into one's eye.

Structural color

Structural color is a property of some surfaces that are scored with fine parallel lines, formed of many thin parallel layers, or otherwise composed of periodic microstructures on the scale of the color's wavelength, to make a diffraction grating. The grating reflects some wavelengths more than others due to interference phenomena, causing white light to be reflected as colored light. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle. Structural color is studied in the field of thin-film optics. A layman's term that describes particularly the most ordered structural colors is iridescence.

Footnotes

# The spelling color is predominant in American English, while colour is used in Commonwealth English. See our/or.

External links and sources

- [http://www.physicstoday.org/vol-55/iss-7/p43.html Comparative Article examining Goethean and Newtonian Color]
- [http://palimpsest.stanford.edu/waac/wn/wn21/wn21-3/wn21-308.html Kruithof curve citation]
- [http://www.soluxtli.com/edu13.htm Article by technical lighting manufacturer on rod/cone vision, with cites to literature]
- [http://www.angelfire.com/psy/reading/Colour.html The Psychology of Colour]
- [http://plato.stanford.edu/entries/color/ Stanford Encyclopedia of Philosophy entry]
- [http://webexhibits.org/causesofcolor/ Why are things colored?]
- [http://www.research.ibm.com/people/l/lloydt/color/color.HTM Why Should Engineers and Scientists Be Worried About Color?]
- [http://poynterextra.org/cp/colorproject/color.html Color, Contrast & Dimension in News Design] Category:Color Category:Image processing Category:Vision ko:색 ja:色 simple:Color

World War I

, and the use of new, devastating weapons - tanks, aircraft, machine guns, and poison gas.]] World War I, also known as the First World War, the Great War, the War of the Nations and the War to End All Wars, was a world conflict lasting from 1914 to 1919, with the fighting lasting until 1918. The label World War I or First World War did not come into general use until after the outbreak of World War II in 1939, and until then it was known as the Great War or the World War. The war was fought by the Allied Powers on one side, and the Central Powers on the other. No previous conflict had mobilized so many soldiers or involved so many in the field of battle. By its end, the war had become the second bloodiest conflict in recorded history (behind the Taiping Rebellion), though it was surpassed within a generation by World War II. World War I became infamous for trench warfare; this was especially true of the Western Front. The trenches went from the North Sea to the border of Switzerland in Europe. More than 9 million died on the war's battlefields, and nearly that many more on the home fronts because of food shortages, genocide, and ground combat. Among other notable events, the first large-scale bombing from the air was undertaken and some of the century's first large-scale civilian massacres took place, as one of the aspects of modern efficient, non-chivalrous warfare. In the First World War 5% of casualties were civilian. In the Second World War that was 50%. World War I proved to be the decisive break with the old world order, marking the final demise of absolutist monarchy in Europe. Four empires were shattered: the German, the Austro-Hungarian, the Ottoman, and the Russian. Their four dynasties, the Hohenzollerns, the Habsburgs, the Ottomans, and the Romanovs, who had roots of power back to the days of the Crusades, all fell during or after the war. The post-war failure to deal effectively with many of the causes and results of the War would lead to the rise of Fascism in Italy, Nazism in Germany and the outbreak of World War II within a generation. The War was the catalyst for the Bolshevik Russian Revolution, which would inspire later Communist revolutions in countries as diverse as China and Cuba, and would lay the basis for the Cold War standoff between the Soviet Union and the United States. In the east, the demise of the Ottoman Empire paved the way for a modern democratic successor state, Turkey. In Central Europe, new states such as Czechoslovakia and Yugoslavia were born and Poland was re-created. __TOC__

Causes

Poland of Franz Ferdinand. The murder was the igniting torch of World War I.]] :See also: Causes of World War I and Participants in World War I On June 28, 1914, Franz Ferdinand, Archduke of Austria and heir to the Austro-Hungarian throne, was assassinated in Sarajevo by Gavrilo Princip, a Bosnian Serb student. He was part of a group of fifteen assassins, acting with support from the Black Hand, a secret society founded by pan-Serbian nationalists, with links to the Serbian military. The assassination sparked little initial concern in Europe. The Archduke himself was not popular, least of all in the Austro-Hungarian Empire. While there were riots in Sarajevo following the Archduke's death, these were largely aimed at the Serbian minority. Though this assassination has been linked as the direct trigger for World War I, the war's real origins lie further back, in the complex web of alliances and counterbalances that developed between the various European powers after the defeat of France and formation of the German state under the leadership of Otto von Bismarck in 1871.

Reasons & Responsibilities

- See also: Causes of World War I There are many different hypotheses that try to explain who, or what, is to blame for the outbreak of the First World War. Early explanations, prominent in the 1920s and 1930s, stressed the official version of responsibility as described in the Treaty of Versailles and Treaty of Trianon, that Germany and its allies were solely responsible for the war. However, as time progressed, scholars began looking toward the rigidity of both German and Russian military planning, each of which stressed the importance of striking first and executing plans quickly. The fact that for many decades the British had been accustomed to colonial wars which were won relatively easily against much weaker adversaries certainly helped build enthusiasm for the Great war. In addition, the fact that no major political force opposed the war meant that those who did not agree with it had little organisational power to build opposition, though small protests continued throughout the war. Another cause of the war was the building of alliances and arms races. An example of the latter is the launch of HMS Dreadnought, a revolutionary battleship that rendered all previous ships obsolete as "pre-dreadnoughts", in 1906. This weakened Britain's power as a seafaring nation and sparked a major naval arms race in shipbuilding, particularly between Britain and Germany due to new imperialism. Overall, nations in the Triple Entente became fearful of the Triple Alliance and vice versa. The civilian leaders of the European powers also found themselves facing a wave of nationalist zeal that had been building across Europe for years. This left governments with ever fewer options and little room to manoeuvre as the last weeks of July 1914 slipped away. Frantic diplomatic efforts to mediate the Austrian-Serbian quarrel simply became irrelevant, as the automatic military escalations between Germany and Russia reinforced one another. Furthermore, the problem of communications in 1914 should not be underestimated; all nations still used telegraphy and ambassadors as the main form of communication, resulting in delays from hours to even days. There is probably no single concise or conclusive assessment of the exact cause of the First World War.

Outbreak of war

ambassadors are depicted in green, the Central Powers in red, and neutral countries in yellow.]] Austria–Hungary was created in the "Ausgleich of 1867" after Austria was defeated by Prussia. As agreed in 1867, the Habsburgs were the Emperors of the Austrian Empire. With the formation of the Dual Monarchy, Franz Josef became leader of a nation with sixteen ethnic groups and five major religions speaking no fewer than nine languages. In large measure because of the vast disparities that existed within the Empire, Austrians and Hungarians always viewed growing Slavic nationalism with deep suspicion and concern. Thus the Austro-Hungarian government grew worried with the near-doubling in size of neighbouring Serbia's territory as a result of the Balkan Wars of 1912–1913. Serbia, for its part, made no qualms about the fact that it viewed all of Southern Austria–Hungary as part of a future Great South Slavic Union. This view had also garnered considerable support in Russia. Many in the Austrian leadership, not least Habsburg Emperor Franz Joseph, and Conrad von Hötzendorf, worried that Serbian nationalist agitation in the southern provinces of the Empire would lead to further unrest among the Austro-Hungarian Empire's other disparate ethnic groups. The Austro-Hungarian government worried that a nationalist Russia would back Serbia to annex Slavic areas of Austria–Hungary. The feeling was that it was better to destroy Serbia before they were given the opportunity to launch a campaign. After the assassination of Franz Ferdinand by Gavrilo Princip and nearly a month of debate the government of Austria–Hungary sent a 10-point ultimatum to Serbia (July 23, 1914) — the so called July Ultimatum — to be unconditionally accepted within 48 hours. The ultimatum was the first of a series of diplomatic events known as the July Crisis which set off a chain reaction and a general war in Europe. The Serbian government agreed to all but one of the demands in the ultimatum, noting that participation in its judicial proceedings by a foreign power would violate its constitution. Austria–Hungary nonetheless broke off diplomatic relations (July 25) and declared war (July 28) through a telegram sent to the Serbian government. The Russian government, which had pledged in 1909 to uphold Serbian independence in return for Serbia's acceptance of the Bosnia annexation, mobilised its military reserves on 30 July following a breakdown in crucial telegram communications between Kaiser Wilhelm and Tsar Nicholas II (the famous "Willy and Nicky" correspondence), who was under pressure by his military staff to prepare for war. Germany demanded (31 July) that Russia stand down its forces, but the Russian government persisted, as demobilization would have made it impossible to re-activate its military schedule in the short term. Germany declared war against Russia on August 1 and, two days later, against the latter's ally France. The outbreak of the conflict is often attributed to the alliances established over the previous decades — Germany-Austria-Italy vs France-Russia; Britain and Serbia being aligned with the latter. In fact, none of the alliances were activated in the initial outbreak, though Russian general mobilization and Germany's declaration of war against France were motivated by fear of the opposing alliance being brought into play. Britain declared war against Germany on August 4. This was ostensibly provoked by Germany's invasion of Belgium on August 4 1914, whose independence Britain had guaranteed to uphold in the Treaty of London of 1839, and which stood astride the planned German route for invasion of Russia's ally France. Unofficially, it was already generally accepted in government that Britain could not remain neutral, since without the co-operation of France and Russia its colonies in Africa and India would be under threat, while German occupation of the French Atlantic ports would be an even larger threat to British trade as a whole.

The spread of war

;1914
- July 23: Austria-Hungary ultimatum to Serbia.
- July 28: Austria-Hungary declares war on Serbia.
- July 31: Russia begins mobilization.
- August 1: Germany declares war on Russia.
- August 2: German troops occupy Luxembourg.
- August 3: Germany declares war on France.
- August 4: Germany invades neutral Belgium; the United Kingdom declares war on Germany in response.
- August 6: Montenegro sides with its traditional ally, Serbia, and declares war on Austria-Hungary.
- August 10: Austria-Hungary declares war on Russia.
- August 12: The United Kingdom and France declare war on Austria-Hungary.
- August 23: Japan declares war on Germany.
- September: Unity Pact signed by France, Britain, and Russia.
- October 9: Belgium falls to German troops at the Siege of Antwerp.
- October 29: The Ottoman Empire enters the war on the side of Germany and Austria-Hungary.
- November 2: Russia declares war on the Ottoman sultanate.
- November 5: France and United Kingdom declare war on the Ottoman sultanate.
- December 25: Christmas Truce in the Trenches. ;1915
- April 25: Gallipoli campaign commences. Turks defeat Allies crushingly.
- April 26: Italy secretly signs the London Pact with the Triple Entente.
- May 23: Italy declares war on Austria-Hungary.
- October 14: Bulgaria declares war on Serbia and enters the war on the side of Germany and Austria-Hungary. ;1916
- March 9: Germany declares war on Portugal (see Portugal in the Great War).
- August 27: Romania declares war on Austria-Hungary.
- August 28: Italy declares war on Germany. ;1917
- January 16: Germany sends the Zimmermann Telegram to Mexico, proposing an alliance against the United States.
- April 6: The United States declares war on Germany.
- June 27: Greece enters the war on the side of the Entente.
- July 6: Arab Revolt troops under Lawrence Of Arabia capture Aqaba, a main sea port for the Ottoman Empire.
- August 14: The Republic of China declares war on Germany.
- October 26: Brazil declares war on Germany.
- November 7: The October Revolution takes place in Russia.
- December 7: United States declares war on Austria-Hungary. ;1918
- January 8: President Woodrow Wilson made his famous Fourteen Points address, introducing the idea of a League of Nations.
- 3 March: Russia and the Central Powers sign the Treaty of Brest-Litovsk, marking Russia's exit from World War I.
- October 30: Mudros/Turkish Armistice signed opening Turkish territory to Entente military operations.
- November 11: Armistice signed, end of World War I. ;1919
- 28 June: Treaty of Versailles, official end to World War I between the Entente and Germany. ;1920
- 4 June: Treaty of Trianon, partition of Austro-Hungarian Empire's Kingdom of Hungary. ;1923
- 24 July: Treaty of Lausanne, peace made with Turkey.
- 29 October: Turkey changes its government to republic.

Opening battles

republic Some of the very first actions of the war occurred far from Europe, in Africa and in the Pacific Ocean. On August 8 1914 a combined French and British Empire force invaded the German protectorate of Togoland. On August 10 German forces based in South-West Africa attacked South Africa. New Zealand occupied German Samoa (30 August 1914) and on September 11 the Australian Naval and Military Expeditionary Force landed on the island of Neu Pommern, which formed part of German New Guinea. Within a few months the Entente forces had accepted the surrender of or driven out German forces in the Pacific. Sporadic and fierce fighting continued in Africa for the remainder of the war. In Europe, Germany and Austria-Hungary suffered from miscommunication regarding each army's intentions. Germany had originally guaranteed to support Austria-Hungary's invasion of Serbia, but the interpretations of this idea differed. Austro-Hungarian leaders thought Germany would cover her northern flank against Russia, but Germany had planned for Austria-Hungary to focus the majority of its troops on Russia while Germany dealt with France on the Western Front. This confusion forced the Austro-Hungarian army to split its troop concentrations from the south in order to meet the Russians in the north. The Serb army, coming up from the south of the country, met the Austrian army at the Battle of Cer on 12 August 1914. The Serbians occupied defensive positions against the Austrians. The first attack came on August 16th, between parts of the 21st Austro–Hungarian division and parts of the Serbian Combined division. In harsh night-time fighting the battle ebbed and flowed, until Stepa Stepanovic rallied the Serbian line. Three days later the Austrians retreated across the Danube, having suffered 21,000 casualties as against 16,000 Serbian. This marked the first major Allied victory of the war. The Austrians had not achieved their main goal of eliminating Serbia, and it became increasingly likely that Germany would have to maintain forces on two fronts. Germany's plan (named the Schlieffen plan) to deal with the Franco-Russian alliance involved delivering a knock-out blow to the French and then turning to deal with the more slowly mobilized Russian army. Rather than invading eastern France directly, German planners deemed it prudent to attack France from the north. To do so, the German army had to march through Belgium. Germany demanded free passage from the Belgian government, promising to treat Belgium as Germany's firm ally if the Belgians agreed. When Belgium refused, Germany invaded and began marching through Belgium anyway, after first invading and securing Luxembourg. It soon encountered resistance before the forts of the Belgian city of Liège, although the army as a whole continued to make rapid progress into France. Britain sent an army to France (the British Expeditionary Force, or BEF), which advanced into Belgium. Initially the Germans had great successes in the Battle of the Frontiers (14–24 August 1914). However, the delays brought about by the resistance of the Belgian, French and British forces; the unexpectedly rapid mobilization of the Russians; and the overly-ambitious objectives upset the German plans. Russia attacked in East Prussia, diverting German forces intended for the Western Front. Germany defeated Russia in a series of battles collectively known as the Second Battle of Tannenberg (17 August – 2 September). This diversion exacerbated problems of insufficient speed of advance from railheads, not allowed for by the German General Staff, and allowed French and British forces to finally halt the German advance on Paris at the First Battle of the Marne (September 1914) as the Entente forced the Central Powers into fighting a war on two fronts. The German army had fought its way into a good defensive position inside France and had permanently incapacitated 230,000 more French and British troops than it had lost itself in the months of August and September. Yet staff incompetence and leadership timidity, as Ludendorff had needlessly transferred troops from the right to protect Sedan, cost Germany the chance for an early knockout.

Early stages: from romanticism to the trenches

Sedan, 1917]] The perception of war in 1914 was romanticized by many people, and its declaration was met with great enthusiasm by these people. The common view was that it would be a short war of manoeuvre with a few sharp actions (to "teach the enemy a lesson") and would end with a victorious entry into the enemy capital, then home for a victory parade or two and back to "normal" life. However, many people regarded the coming war with great pessimism and worry. Many military figures, such as Lord Kitchener and Erich Ludendorff, predicted the war would be a long one. Other political leaders, such as Bethmann Hollweg in Germany, were concerned by the potential social consequences of a war. International bond and financial markets entered severe crises in late July and early August reflecting worry about the financial consequences of war. The perceived excitement of war captured the imagination of many in the warring nations. Spurred on by propaganda and nationalist fervor, many eagerly joined the ranks in search of adventure. Few were prepared for what they actually encountered at the front. See also: Recruitment to the British Army during WW I

Trench warfare begins

:Main article: Western Front (World War I) Advances in military technology meant