Thanks for the link Rhody. Thanks to the anonymous member, too. I’m afraid this will be a rushed post.
Firstly, it was interesting for the differences between the two experiences that you mention.
The paper (which allows for various possibilities), regarding auditory-visual synaesthesia, says-
“The marker obtaining
the highest LOD score (D2S142, with HLOD ¼ 3.025) has
been linked to autism.32 Synesthesia is sometimes reported
as a symptom in autism-spectrum disorders,33 and sensory
and perceptual abnormalities are a significant feature of
ASDs.34,35 Clinical reports indicate a potentially elevated
prevalence of synesthesia among people with autism-spectrum
disorders, as well as sensory overload similar to that
reported by synesthetes (S.B.-C., unpublished data). Auditory
stimuli trigger responses in both auditory and nearby
visual brain regions in autistic individuals36 as well as auditory-
visual synesthetes.14 Neuropathological studies have
detected abnormally increased connectivity in the brains
of individuals with autism,37 and alterations in white
matter that could indicate increased connectivity have
been observed in the brains of synesthetes;15 neuropathological
studies of the brains of synesthetes would
contribute significantly to the further elucidation of the
underlying neural architecture. A recent case study indicates
that savantism, long thought to be connected with
autism, may in some cases result from the combination
of autism and synesthesia.38 “
As you say ASD and synaesthesia generally appear to feature differences in information processing.
Possibly these are contrasts as, generally, one may involve ritual, restricted interests and restricted imagination while the other is speculated to be related to creativity. Away from the topic a little, as there is nothing expressly about synaesthesia, this paper discusses the relationship between creative, artistic types (with a tendency to unusual experiences and their association with divergent thinking) and autism (with convergent thinking)-
http://www.staff.ncl.ac.uk/daniel.nettle/jrp.pdf
Another difference could be that one features difficulty with typical expressions of cross-modal perceptual experience, such as recognising faces and symbol interpretation, and the other consists of more cross-modality than seemingly usual.
Another difference could involve deficits in anticipation in autism. Ventriloquism and the McGurk effect are typical cross-modal illusions. Changizi says typical illusions may assist anticipation-
http://www.nytimes.com/2008/06/10/health/research/10mind.html . If these are anticipatory, than perhaps forms of intra or cross-modality which also respond in one mode to stimuli in another, but which are atypical, may also assist anticipation.
Also, another difference is that problems with social interaction, imitation and response to emotions are noted in one, whereas mirror synaesthesia, for example, involves imitative interaction and is linked with strong empathy, and generally, synaesthetic responses are notably emotional.
Thanks for the link to the Einstein thread, too. It is something I haven’t considered, but funnily enough, I’d mentioned Einstein’s thought processes in a post not long before your thread, that sound possibly cross-modal, although possibly not perceptual (perhaps even given Deheane’s work, and also that of Brouwer, and Davis and Hersh on the matter of mathematical perception), also possibly not involving a lot of other criteria that defines synaesthesia, whatever that may be, and possibly not atypical (but then, what way of coming up with Einstein’s theory of relativity is typical:) ).
In one instance, my post referred to a letter Einstein wrote in response to the mathematician, Hadamard’s survey about thought processes in fellow field medallists, etc., in which Einstein states that rather than thinking with words or communicable signs, there is first a “combinatory play” of visual and muscular(kinetic?) signs and images felt to be analogous to logical connections, as replicated here in pages 32 and 33-
http://books.google.co.uk/books?id=...=onepage&q=einstein hadamard muscular&f=false
And in another quote from an interview, which may be out of context, because he is talking about how important music is to him, with the “Saturday Evening Post”, 26, Oct, 1929, cited in Calaprice, 2000, Einstein said “…I often think in music”.
And regarding what is typical, regarding world class mathematicians intereviewed by Hadamard, Hadamard found that "Practically all of them...avoided the use of mental words ...as I do, (as well as) the mental use of algebraic or any other precise signs... The mental pictures...(used) are most frequently visual, but they may also be of another kind, for instance, kinetic. There can also be auditive ones, but even these quite generally keep their vague character." Although being world class may still set them apart from what is typical, too.
