Omaha fricative set

[Rankin, Robert L]

This sort of question is what that paper on "The Mediaeval Sibilants" is about.  Apical S's were fairly widespread in Europe.  They still appear in Greek, Basque, Castilian, Aragonese and Catalan (all but Greek in a narrow geographical area).  I can't remember about Leonese or Asturias, but I don't think so.  In English either apical or laminal pronunciation is accepted.  John mentioned Humphrey Bogart's S.  Jimmy Stewart is another apical speaker and the pronunciation is characteristic of central Pennsylvania English, since I have it sometimes as well.
 
"Features" can be looked at two ways.  You can ask whether phoneme X is realtively "distributed" with respect to phoneme (or phonological series) Y, or you can try to set some sort of inflexible physiological parameters for "distributed", like dyed-in-the-wool phoneticians try to do.  The latter almost always encounter failure in one or another language.  In phonology (i.e., linguistics) features are usually "relative" in the Jakobsonian sense.  In Speech departments, they attempt the phonetic definitions.  So, in English /s/ is not apical or laminal with respect to any other variety of S (since English only has one phoneme /s/).  English /s/ IS "non-distributed" with respect to /theta/, which IS "distributed".  It then differs from English /s^/ by a different feature.  The phonetic and phonological definitions of distinctive features can be a little confusing, because different specialists approach the topic with completely different assumptions/definitions.  

> >  So does this mean that in English /s/ is "apical" and /s^/ is
> > "distributed"?  
 
> My impression is that /s^/ in English at least (and probably most
European languages) is almost never apical. A pronunciation with the
tip of the tongue would cause the fricative surface to be too small
for a "distributed" specification. Rather, /s^/ for me at least seems
to be pronounced significantly behind the tip of the tongue. If I
attempt to pronounce an apical /s/ in the same site as /s^/, what I
get is a retroflex.