Humans have an instinctive need to communicate with each other, which we primarily accomplish through spoken language. However, this presents a challenge for deaf people, who struggle to learn and speak an auditory language. As a result, cultures have developed visual languages to replace spoken ones. While most people are aware of the existence of sign language, its complexity and history are not well-known.
Sign language is a form of communication that primarily consists if different hand gestures to demonstrate different concepts. Most sign languages consist of both a manual alphabet, where different hand positions represent specific letters that allow the signer to spell out new or difficult words, as well as a complex vocabulary of more complex signs that represent words, phrases, and ideas. Some signs may also incorporate body posture and facial expressions.
Forms of sign language have been documented in almost every culture in the world. For areas with small deaf communities, this sometimes takes the form of home sign, where each family with a deaf member develops their own unique language. Most countries have their own version of sign language, including France, Sweden, Denmark, the United States and more. Some hearing cultures have also developed sign languages for other reasons. The Native Americans of the Great Plains had a universal sign language they used to communicate with each other despite having different spoken languages.
Sign language is not a modern concept. The earliest known written mention of sign language may be a passing reference made by Socrates in the fifth century B.C.E. Several drawing of manual alphabets exist from the sixteenth and seventeenth centuries C.E., with further references to more complex languages. The details of those languages have been lost, however. The 19th century saw an increased interest in educating and communicating with deaf people and was when modern sign languages were developed and codified.
Prior to the widespread use and acceptance of sign language, many hearing people believed that deaf people were incapable of learning to communicate. This was largely due to the difficulty of communicating with them. Sign language changed things and showed that deaf people are just as intelligent and capable as hearing people. One famous pioneer in that regard was Helen Keller, who was both deaf and blind due to a childhood illness. She learned to speak and became a popular lecturer and public speaker, but she first learned to communicate using signs. Her teacher, Anne Sullivan, would sign words against Keller's palms so Keller could feel them.
Many people assume that signing is simply a physical representation of a particular spoken language, but that is untrue. Instead, sign languages are linguistically unique and often bear little or no resemblance to the primary language spoken in that country. For example, the United States, the United Kingdom, and New Zealand all have their own sign languages. The U.K. and New Zealand versions are closely related, but American Sign Language is closer to French Sign Language, despite English being the primary spoken language of all three countries. There are even regional dialects within a single language.
Language helps create and shape our cultures, which has led to many deaf people experiencing a slightly different culture than the hearing communities around them. Sign language has its own idioms, expressions and even forms of humor that may not translate well to spoken language. This is usually described as Deaf culture, with the "D" capitalized, although Deaf cultures can vary by region and country.
Beginning in the late 20th century, it became popular for parents to use a limited form of sign language with hearing infants. This can be an effective way to communicate with very young children since children are often able to understand and make simple signs before they can speak. However, baby sign is not a true sign language since it only works in conjunction with spoken language.
In areas where sign language is more common, most of the hearing community also knows some sign language and often signs while speaking for better conversation. Martha's Vineyard Sign Language is an example of this in the United States, though it has not been widely in use since the 1950s.
Sign language interpreters are also widely available to help deaf people interact with a broader community. They are often seen at major entertainment events, but they also perform a lot of one-on-one work behind the scenes.
Written forms of sign language are uncommon, as many deaf people can write in the spoken language of their country and don't believe they need a separate form of written communication. However, some people have tried to create a written version. Most are simple phonemic representations that do not capture many of the nuances of sign language, but they can be useful for transcription and research purposes.
One of the drawbacks of sign language is the difficulty in communicating by over-the-phone since two people need to see each other's signs. This was actually one of the driving forces between the development of video calling. A sign conversation was even used as a demonstration for the first effective video calling technology, which was unveiled at the 1964 World's Fair. A person in New York, where the fair was held, was able to hold a sign language conversation with a person in another city. Today, deaf people frequently use video calling apps to keep in touch.