A subset of visual iconicity involves a spatial iconicity. However, their popularity is due to their iconicity. Signed languages are transmitted visually and this allows for a certain degree of iconicity. Bee dances are another example of iconicity in animal communication systems. Gunning states that a photograph must also have "iconicity". Despite this, a few captive chimpanzees have shown the beginning stages of iconicity. Iconicity occurs in rejective phono-semantic matching. Whether iconicity is a part of language is an open debate in linguistics. It has been suggested that iconicity can be used in the teaching of languages. As a result, iconicity as a whole was largely neglected in research of sign languages. Iconicity is expressed in the grammatical structure of sign languages called classifiers. Iconicity is independent of actual connection, even if it occurs because of actual connection.