Many forms of signing exist. Sign systems of various forms have been developed among Trappist monks, for children with certain learning disabilities, and for various other reasons. This entry, though, is concerned only with actual signed languages - the natural languages of the world's deaf communities.
These make use of a spatial grammar, which is in many respects quite different to the linear grammar of spoken languages. Signed languages therefore provide a lot of valuable information for researchers examining linguistic universals: which aspects of grammar are common to all languages, and which are peculiar to certain families or modes (spoken, signed, written) of language?
It is hard (perhaps impossible) to study a language without having some way to write it down. You certainly need to annotate examples in published research papers. Signed languages are often glossed into another language: words from a spoken language are written in sign order, and annotations inserted for other aspects of the language, such as head shakes and nods, blinks, direction of 'eyegaze', and indexing (pointing).
Glossing, though, is unsatisfactory for many reasons. The most obvious is that many words do not have a simple one-to-one correspondence between languages, so the spoken-language word chosen to represent a certain sign is to some extent arbitrary. Also, the annotations are not perfect, and cannot represent the bare, unanalysed data. Some interpretation (such as the focus of an index) is done by the person writing the gloss, so the gloss itself is not an unbiased source for other researchers.
In the course of his research, Stokoe created a notation system for writing signs. And Stokoe notation became popular with sign linguists. Although it was created for ASL, it could be adapted for other sign languages. Indeed, Stokoe notation is used in the gigantic Dictionary of British Sign Language1.
Stokoe notation consisted of three elements: the handshape (dez), location (tab) and movement (sig). Symbols for each of these are written in a set order to describe signs. The British Sign Language (BSL) dictionary lists 57 handshapes. It also uses a set of symbols for orientation (ori). The same symbols are used for palm and finger orientation, which is one reason why a strict order of writing the signs is necessary.
For single-dez signs (using only one hand), the standard order used is 'tab-dez-ori-ori-sig'. For manual tab signs, where two hands are involved but only one moves, the standard order is 'tab-ori-ori-(ha)-dez-ori-ori-sig'2. And for double-dez signs, where both hands move, the standard order is 'tab-dez-ori-ori-(ha)-dez-ori-ori-sig'. When sig symbols are written in a vertical column, the movements are all happening at once. When they are in horizontal rows, the movements happen one after the other (reading from left to right). For movement and orientation symbols, the words 'left' and 'right' refer to the signer's perspective, not that of the audience.
Stokoe notation is useful for encoding signs in a dictionary or the study of sign linguistics. But using it to actually write signed languages is near impossible. The symbols cannot be read fluently. Indeed, Karen van Hoek compared Stokoe notation with writing English with all the letters in alphabetical order, with little numbered subscripts to tell the order in which to pronounce them. H2i3s4t1 i1s2 a9b10c3d1e2e7e12h6i4l11p5r8, b1t3u2 a2d4h1l5r3y6 e9i1i5i7n2t3t6u4v8.
Stokoe notation does not encode any information about non-manual features, which includes facial expressions and movements of the head, shoulders and trunk. The introduction to the BSL dictionary lists 46 non-manual features, including 'The eyebrows are raised', 'The eyebrows are furrowed', 'The cheeks are puffed out', 'The lips vibrate', 'The tongue protrudes', 'The tongue tip is held between the lower lip and the bottom teeth', 'The eyegaze is directed down and forwards', 'The eyegaze is directed in line with the movement of the hand', 'The eyes open', 'The eyes close', 'The eyes are closed', and 'The shoulders are hunched'. These are all essential parts of the signs in which they occur3.
One problem with Stokoe notation is that the labels given to handshapes are to some extent derived from the US manual alphabet4. This makes it a bit strange when applied to signed languages with different manual alphabets. For example, the Irish manual alphabet handshape for 'G' is called an 'F-handshape' in Stokoe notation. When applied to the British manual alphabet, which is two-handed, the system seems arbitrary.
Stokoe notation will only take us so far; it is not detailed enough for some researchers. So another method was developed. HamNoSys (or the Hamburg Sign Notation System) is, like Stokoe notation, a linear method of writing signs. It can show wrist orientation in far more detail than Stokoe notation.
The symbols for handshapes are far more iconic than Stokoe's, so they are easier to learn and universally applicable.
HamNoSys was developed by a group of deaf and hearing people at the University of Hamburg, as a research tool. It was first made publicly available in 1989.
Sutton SignWriting is very different to other sign notation systems. For a start, it was created not by a linguist, but a dancer. The US citizen Valerie Sutton was training as a dancer when she created a system to record dance steps; she worked with the Royal Danish Ballet to record historic dance steps which were in danger of being forgotten.
In 1974, a group of sign researchers headed by Lars von der Lieth at the University of Copenhagen came across articles about Sutton DanceWriting. They approached Sutton and asked her to create a similar system for notating signed languages.
She watched hours of sign language videos which she did not understand, so created the first sign notation system which is purely descriptive, and not at all based on underlying grammatical principles. Sutton SignWriting is not a linear method: information about hand orientation, location and shape is all written together. Being the most iconic form of notation, it is also the easiest to learn. It is not, however, as detailed as HamNoSys.
The system was gradually improved over the years, with Sutton always involved.
The other major difference between Sutton's method and the others is that it is very easy to simplify SignWriting slightly to create a writing system. HamNoSys and Stokoe notation are exactly that: notations used by linguists. Sutton SignWriting is also often used by linguists, but can also be used to write letters, newspapers, even, potentially, novels. Being purely physically descriptive - not based on the grammar of handshape - it can also be used to write almost any sign language. And, because it is related to Sutton DanceWriting5, it can be easily expanded for those occasions when a signer gets excited (or starts playing with language, as in poetry or humour) and moves outside the normal constraints of the language to use leg, feet or full body movements.