4.2 Functional categories of gestures

As illustrated in Table 1, CoGesT classifies gestures as either gestural idioms or non-conventionalised gestures. This is a theoretical classification which still needs to be verified empiricaly. Both types of gestures can occur with or without parallel speech. When gestures function as gestural idioms, they have one particular meaning associated with them, which is understood in a particular cultural group. Two types of gestural idioms can be distinguished: The first type of gestural idioms in conversation have the same lexical status as signs in sign languages. This type of gesture includes gestures called ``emblematic'' by Kendon (1988) and McNeill (1992). Gestures classified as ``deictic'' (e.g. pointing at someone or something or a direction in space) by McNeill (1992) are also subsumed in this category when or when not accompanied by speech. An example for a gestural idiom of type one without speech is nodding in German, which stands for `yes' and wagging the forefinger from one side to the other, which is understood as a warning `no' or `don't'. Gestural idioms type one can also be produced parallel to speech, for example, when giving the `ok' sign in English by forming an `O' with the thumb and forefinger and saying ``ok'' at the same time. In some conversational situations (depending very strongly on the knowledge and the degree of familiarity among the participating conversational partners), such an overlap might be perceived as redundant information by the interlocutor(s). The second type of gestural idioms does not have a lexical but rather a discourse-structuring meaning. A gestural idiom type 2 is for example the rotation of the wrist while snapping one's fingers which signifies that the speaker is searching for a word and wishes to keep her turn. Some held postures can probably also be classified as gestural idioms of this second type. A person folding their arms in front of their chest might be regarded by an observer as expressing ``a defensive or negative attitude'' (Pease, 1997, p. 60).

Non-conventionalised gestures do not have an immediately apparent meaning by themselves. They can, in some situations, serve to embellish or underline the meaning of the speech produced. An example of this type of gesture produced parallel to speech is a movement of the hand to illustrate the shape of a leg whilst describing someone's legs. It is theoretically possible to produce such a gesture with a time lag to the corresponding unit of speech. However, further research will show whether this really occurs, and how big the time window for such a case is. This category comprises what Wundt (1973) calls ``affective gestures,'' and McNeill (1992) classifies as ``metaphoric.'' They also comprise Ekman & Friesen's ``kinetographs'' and ``ideographs'' (see Ekman and Friesen, 1969). This category also subsumes the category of ``beats'' as described in McNeill (1992), which have been claimed to be aligned with prominence and rhythmic patterns, and ``batons'' (Ekman and Friesen, 1969) which have been claimed to coincide with speech rhythm.