I hope you can help me with this matter about phonetics. I couldn't prove that there actually existed progressive assimilation for /s/ to become /ʃ/. […]
I have been doing some online research about it, but didn't manage to find anything about it. I also asked around, but it was denied that there existed such assimilation. Your dictionary also states that there [is] only regressive assimilation.
Nevertheless , the notes I was given by my Phonetics teacher included this type of assimilation. Here is an example of it:
bookish style /bʊkɪʃ staɪl/. If there is assimilation: /bʊkɪʃ ʃtaɪl/
Have you ever heard of this before?
No, I haven’t. My immediate reaction was that this type of assimilation simply doesn’t happen. That’s why Ernesto can’t prove that it does, and also why he can find no reference to it in his on-line search.
However, phonetic research is not just a matter of finding out what published descriptions say about this or that phenomenon (in this case, they seem to say nothing). Genuine research involves making observations: observing and analysing what speakers actually say. I told Ernesto he should
Collect some evidence, and see what you find.
The phonetic context we are interested in is by no means unusual. Plenty of possible examples come to mind.
cash some cheques
wash six pairs of socks
Does anyone know of any research into the phonetics of such ʃs sequences?
Introspecting, I feel pretty confident in saying that full-blown progressive (= perseverative) assimilation, thus ˈbrɪtɪʃ ˈsɪtɪzn̩ → ˈbrɪtɪʃ ˈʃɪtɪzn̩, just doesn’t happen. Nor does full-blown regressive assimilation, thus ˈbrɪtɪs ˈsɪtɪzn̩. However some kind of intermediate allophonic regressive assimilation, perhaps ˈbrɪtɪɕ ˈsɪtɪzn̩ or somethinɡ similar, seems possible.
I stick by my view that in English progressive assimilation is restricted to
(i) morphological assimilation of voicing, producing s in cats and t in kissed (compare dogs with z and raised with d);
(ii) assimilation of syllabic n̩ to the place of a preceding obstruent, as in ribbon (ˈrɪbən →) ˈrɪbn̩ → ˈrɪbm̩.
I think Ernesto’s phonetics teacher was wrong. In English phonology, features typically spread leftwards, not rightwards.