A commenter at Steve Sailer's asked what they hell I meant by social signalling, in discussing language usage. We have used the term often enough here that I have fallen into the assumption that I am being clear. Let me make sure.
The dominant dialect in any language is often rather accidental. The ruling class usually declares its dialect to be standard, officially or not. Most frequently, this is the dialect from around the capital city. If you come from the provinces, your charming accent and phrasing, which sounds like the Only True Frubish to you, will brand you as a stupid person.
That's the simplest form. In actual countries there may be competing dialects, or a particular brand may be considered especially well-suited for a certain type of person, such as a preacher to the masses, or an international trader. It can get complicated - no need to go into that here.
In America, standard English tracks central Ohio pretty well, at least as I was taught in the 1970's. What we consider accentless has spread far enough by mass media that many regional accents are barely noticeable. Both Portlands speak a similar dialect*. Those regions or groups which retain identifiable accents sometimes suffer under stigma. In America, we can get assertive rather than apologetic about this and make the stigma swing the other way for our own purposes. Obama was being held at arms length by much of the black community until he verged into mild black dialect - most famously on Oprah; newscasters with NYC accents are not going to get jobs in some places, and certainly not in Chattanooga.
The most prestigious dialect in America varies by listener. The more one is a reader of older material, the more one likes a speaking style that tracks written standards. This style uses slight archaisms, pronounces consonants (because the written form is present in the mind), keeps track of implied punctuation, and uses slang for effect rather than naturally. None of us has a speaking style that is all that close to written English, actually. But some dialects are much closer than others.
Less formal, folksier dialects are preferred by a great many Americans, including some extremely well-educated ones. In Australia as well, there is a tradeoff of sounding too educated - not because education is not prized, but in the subtle twists of social communication, veering too far into formal, written dialect raises the question whether you might not be truly egalitarian, truly American.
A young African-American man from mid Long-Island was admitted today, and his accent mixed New York and black styles. He said cooffee, he said breave (for breathe). His vocabulary seemed large enough and expression clear enough that he is likely above average intelligence. But outside of his region or race he will certainly sound strange, and probably less intelligent. If he wished to live elsewhere or enter many professions, he would have to learn an American dialect closer to Ohio white, using his familyspeak selectively or for effect. This partly true for all of us - I am quite aware that my dialect has changed slightly over the years - but more for some than others.
He is a native English speaker, and a linguist would regard his dialect as being "as good" - whatever that means - as North Georgian, Rural Vermont, or Upper Peninsular. But using dialect signals who we are, or want to appear to be. Why do African Americans give their children more unique or eccentric names, in contrast to earlier onomastics of naming after famous people? Likely, to show solidarity with the black community and independence from the implied one-down-ness of imitation. Why do New Yorkers keep that accent they know everyone else hates? Because they consider much of the hatred to be envy, and want to identify with The City.
Not splitting an infinitive marks one as trained in a certain era with certain aspirational values and attention to detail. No one does it naturally, it can only be learned by attention and practice. I no longer worry about it (much), which signals something about me.
*Yes, they might have because of founder effect anyway, but really - not really.