I have seen scholars claim that...
"sign languages are simultaneous whereas spoken languages are linear".
In my opinion, however, the notion of "linearity" vs. "simultaneity" is misleading at best.
Sure, the modality of sign languages, the "optical signal", makes it possible to view the articulatory gestures directly, whereas in spoken languages they are mostly invisible and only indirectly "transmitted" through the acoustic channel by means of speech signal.
Yet from the speech signal, by means of a complex bundle of frequency and amplitude information (which is an awful simplification, admittedly), quite a lot of meaningful linguistic information can be extracted simultaneously, such as vowel quality, pitch etc.
When we move on to morphology, we can clearly refer to the many kinds of non-concatenative/nonlinear morphology, such as apophony, be it manifested by tone and/or stress patterns, vowel/consonant gradation etc.
I have also seen people claim that...
spoken languages are 1D (one-dimensional), while sign languages are 3D (spatial).
That, too, seems somewhat strange to propose: apart from the reasons mentioned above, do articulatory gestures not occur in space? True, they cannot be seen, but we could just as well say that the articulatory gestures of sign languages cannot be heard.
I am not a user of a sign language and my knowledge of sign languages is extremely limited, but my impression has been that the options for employing simultaneity may well be considerably wider only thanks to the character of the communication channel, and that the options can be compared, albeit loosely, imperfectly and a bit ad hoc, for example, as follows:
- laryngeal / jaw angle / velum lowering ~ facial
- labial ~ left hand
- bilabiality / labiodentality / protrusion / compression ~ left-hand fingers and their configuration
- coronal ~ right hand
- tongue-tip/blade configuration ~ right-hand fingers and their configuration
- consonants ~ locations
- consonant transients in vowels ~ movements between locations
And so on... Just like with spoken language we may refer to the notion of tiers and autosegments, even if the feature geometries are largely, if not completely, different.
Would both experts on spoken and sign language agree if I stated that...
spoken languages are articulated internally and thus transmitted indirectly, while sign languages are articulated externally and thus transmitted [more] directly?
It could also be this very directness that would make iconicity easier to employ and, indeed, employ it more widely, transparently and systematically, whereas the indirectness of the spoken languages would make the use of iconicity more constrained and difficult to utilize.
On the other hand, I have also come across an article mentioning something that may, indeed, be unique to sign language, and even truly three-dimensional: spatial deixis. Although it effectively weakens, if not cancels, my anti-3D stance, we can still keep it apart from simultaneity and say that sign languages can employ the external 3D space to express spatial deixis, which spoken languages cannot.
I will be grateful for any relevant suggestions, references or simply comments.
P.S.: I have just discovered the question Simultaneity in natural languages? discusses somewhat similar issues, but, hopefully, mine is still different enough to deserve its existence. :-)