The Greater Potential Of Gestural Resources For Iconicity

Halliday & Matthiessen (1999: 534):

Gestural systems, by contrast, have a far greater potential for construing experience iconically. Thus in Johnston (1989: 16) "signs are roughly graded into four classes of transparent, translucent, obscure and opaque signs, depending on how iconic a sign is"; and while most signs fall in between the two extremes — Johnston grades them as obscure or translucent, rather than opaque or transparent — many of those he labels "obscure" have a popular explanation in iconic terms (e.g. 2388: n. CAMERA, v. TAKE A PICTURE, PHOTOGRAPH. Obscure action. Popular explanation: 'holding a camera and depressing the shutter button' [p. 301]). This suggests that even if particular explanations are "nothing more than deaf folklore" (p. 16), the system as a whole is perceived as prototypically iconic; and this feature is borne out in two important respects. 

One is that many of the signs construing basic categories of experience that would be learnt very early in childhood, in the transition from protolanguage to mother tongue — examples are 1291 GET; 1479 HOLD; 1824 RUN; 2473 BIRD; 2759 DRINK, CUP; 36 BED; 163 UP — are clearly iconic, and so would tend to establish iconicity as the norm. 

The other is that individual signs may be modified in a distinctively iconic fashion; e.g. 1471 "v LARGE, BIG, (with amplification) great, (with amplification and stress) enormous, huge, immense"; see in particular the section on "sign modification" in Johnston (1989: 494-9). As Johnston comments (p. 513), "A language which is itself visual and spatial has far more opportunities than an auditory one to map onto itself those very visual and spatial qualities of the world it wishes to represent".

The Limited Potential Of Vocal Resources For Iconicity

Halliday & Matthiessen (1999: 533-4):

We have referred all along to the primarily visual nature of human experience: how much of it is constituted as location, and especially movement, in space. Now, both gestural and vocal resources involve positioning and moving the organs of articulation in space; but the position and movement of the vocal organs, besides being largely out of sight of the listener, is very much mote constrained; and while this permits a limited degree of iconicity (association of close vowels with 'small', open with 'large', for example) this can never be more than a marginal feature of the system as a whole. Thus even allowing for the additional iconic potential of loudness and length, the expression systems of spoken languages must remain prototypically conventional. This is the familiar principle of the "arbitrariness" (i.e. conventionality) of the linguistic sign.

The Potential Of Vocal And Gestural Expressions For Construing Wording

Halliday & Matthiessen (1999: 533):

In the most immediate sense, as regards their potential for construing signifiers — elements of wording and their arrangement in combination — both these forms of expression, vocal and gestural, are open-ended. Neither of them imposes a limit on the inventory of morphemes or their configuration in grammatical structures. Nevertheless they are significantly different in the kinds of resource they offer for making meaning. Perhaps the major difference between the two is their potential for iconicity.

The Construal Of Experience As Semantic Space In Signed Languages

Halliday & Matthiessen (1999: 535):

From Sign, we get further insight into the construal of experience as ideational meaning because of its greater potential for iconicity in the expression. Semantic space can be construed iconically in signing with continuous space-time, constituted as bodily experience for the signer and as part of shared visual experience for signer and addressee.