One of the most recognizable traits of American speech in the South and Southwest is the so-called “pin/pen merger,” a shorthand phrase meant to designate the non-distinction of the front vowels /i/ and /e/ before the nasal consonants /m, n, ŋ/. The vowel that appears in this position is identified with the realization of the high front vowel in pin, whim, and sing. Speakers who have this trait do not distinguish between the pronunciation not only of minimal pairs like pin and pen or fin and fen but of any word that has a front vowel before a nasal consonant (whatever the spelling), so that one hears m[ɪ]mber for Standard American English m[ɛ]mber, m[ɪ]ntality for SAE m[ɛ]ntality, etc.
People who have this trait need not be speaking in an identifiable dialect. In fact, it may be the only remnant of a regionalism in what is otherwise SAE speech. For instance, just this morning I heard three announcers/reporters on NPR (Renée Montagne, Deborah Byrd, Richard Harris) who display this trait but are otherwise speakers of the standard.
Thus, despite the constant migration of people from place to place over their lifetimes, the impact of education and the media typically results in an American standard that is largely free of dialectal or regional traits––with the prominent exception of this one, which is properly to be labeled a NEUTRALIZATION. A neutralization is the reduction (G Aufhebung) of an opposition to one of its two terms. Technically, one speaks here of the realization of an opposition in a position of neutralization (= context). Typically, an opposition that is neutralized in a certain context is realized as (identified with) one of its two terms––to the exclusion of the other, but also of any third term: tertium non datur (there is no third term).
Despite the familiarity of the “pin/pen merger” to linguists as a fact of dialect geography, its status and attendant meaning specifically as a neutralization have not become part of language lore. Neutralizations throughout grammar (i.e. not only in phonology) have an interesting sign function. In positions of neutralization it is normal for the realization of the opposition to be identified with the unmarked (generic) term. Thus, for instance, when the sex of the referent is immaterial one finds words of the unmarked masculine gender referring to both sexes (“Man is an animal.”). In the case of the two front vowels in question, /ɪ/ as a high vowel is unmarked vis-à-vis the marked non-high /ɛ/ in the opposition high/non-high. Hence this phonological case conforms in sign function to the general principle that it is the unmarked member of the opposition that appears as the representative of the opposition in a position of neutralization.
In language, the sign function of neutralization is unitary––whatever the concrete realization depending on context, to which it is uniformly sensitive. Neutralization is a fundamental means by which both users (initially, qua learners) and analysts––unconsciously in the first case, consciously in the second––are provided with the material evidence that linguistic variation is not haphazard but structurally coherent, where coherence is measured by the systematic, patterned cooccurrence of units and contexts in tandem.