American Sign Language

American sign language, or ASL, is a communications-based decryption element, established as a visual way of communicating for deaf or hearing-impaired people. While less commonly-used in puzzle hunts than other communications-based elements, it and finger binary remain the two most prominent ways of expressing individual letters via hand positions.

Background
See also: American Sign Language

Sign language as a whole has a long history beyond its modern use as a deaf aid. Original use was to allow communication across linguistic and cultural boundaries, and is documented at least as far back as 1541, when its use by natives of the Great Plains was recorded by Francisco Vásquez de Coronado.

Modern sign language for use by/with deaf people in the US has origins in New England, where a trifecta of sign languages emerged in the communities of Martha's Vineyard, Henniker, and Sandy River Valley. Martha's Vineyard Sign Language, or MVSL, was particularly well-developed, due to the high rate of genetic deafness in the community, and the necessity of communicating with deaf community members. What we now know as ASL, however, likely originated in Hartford, Connecticut at the American School for the Deaf, when a large group of people from all three of these communities attended during the first few years of the institute being open. A mix of the three sign languages, as well as the French Sign Language taught by the first teacher at the school, ended up evolving into today's American Sign Language.

Puzzle Applications
Despite (or perhaps because of) the wide range of words. phrases, and dialects available across all of ASL, the most common way the language is used in puzzles is via the American Manual Alphabet, or AMA. Since the AMA is taught even to non-ASL speakers, it's often considered to be common knowledge (to some degree). Additionally, all of the letters are displayed single-handedly, which allows them to be hidden within pictures and videos without making it totally obvious that ASL is being used.

Puzzles tend to use AMA in one of two cases: either as an extraction method, wherein a small number of hand symbols are presented to get across a short word or phrase; or as a full encryption, wherein long strings of text are replaced with video/images of someone performing a string of hand symbols or with hand drawings/Unicode characters.

When puzzles do use words and phrases in ASL, they'll often use a specific source, as varying referenced may result in gestures coming from different dialects. Conversely, puzzles rarely use translations from written English to ASL, particularly due to the large number of varying sources. For example, the word "about" has at least six different ways to sign it depending on use and locale. As such, unless a source is specified or connecting factors are included that allow solvers to identify the correct source, English-to-ASL word translations should be avoided.

Played Straight

 * Quagmire (MITMH 2004) - After the maze in the puzzle is solved, the path taken traces out some AMA letters, spelling out the final clue phrase.
 * Louder Than Words (MITMH 2006) - A rare case of English-to-ASL translation. Uses groupings based on common hand-shapes to help determine a consistent source.