African American Vernacular English : Features, Evolution, Educational Implications (Language in Society (Oxford, England), 26.) by John R. Rickford; the foreward is by Labov.
Or McWhorter, John H. The word on the street : fact and fable about American English. John McWhorter. New York : Plenum Trade, c1998.
They come to different conclusions. Here is an excerpt from the former; then the latter. I think Rickford is a prof at Stanford; McWhorter one at UC Berkeley. ________________________
Yet Ebonics is one of the most distinctive varieties of American English, differing from Standard English--the educated standard--in several ways. Consider, for instance, its verb tenses and aspects. ("Tense" refers to when an event occurs, "aspect" to how it occurs, whether habitual or ongoing.) When Toni Morrison referred to the "five present tenses" of Ebonics, she probably had usages like these--each one different from Standard English--in mind:
1. He runnin. ("He is running.")
2. He be runnin. ("He is usually running.")
3. He be steady runnin. ("He is usually running in an intensive, sustained manner.")
4. He bin runnin. ("He has been running.")
5. He BIN runnin. ("He has been running for a long time and still is.")
In Standard English, the distinction between habitual or nonhabitual events can be expressed only with adverbs like "usually." Of course, there are also simple present tense forms, such as "he runs," for habitual events, but they do not carry the meaning of an ongoing action, because they lack the "-ing" suffix. Note too that "bin" in example 4 is unstressed, while "BIN" in example 5 is stressed. The former can usually be understood by non-Ebonies speakers as equivalent to "has been" with the "has" deleted, but the stressed BIN form can be badly misunderstood. Years ago, I presented the Ebonics sentence "She BIN married" to 25 whites and 25 African Americans from various parts of the United States and asked them if they understood the speaker to be still married or not. While 23 of the African Americans said yes, only of the whites gave the correct answer. an real life a misunderstanding like this could be disastrous!) _________________________
Here's a review of McWhorter's book:
In the first section of this enlightening book, McWhorter (linguistics, Berkeley) examines language as "a system that is at all times on its way to changing into a different one." Not only are new slang and technical terms added, but sounds, structure, and meanings change over the centuries. McWhorter assures us that linguists have never "encountered any languages whose changes compromised their basic coherency and complexity." So in Part 2, he recommends "translating" Shakespeare into modem English, suggesting that foreigners appreciate the bard more than English speakers because his words are translated into their own vernacular. With wit and logic, McWhorter argues that word distinctions that enhance communication are worthwhile; quirky grammar roles are not. His concluding section based on research conducted during the 1996-97 Oakland classroom controversy, demonstrates that black English is a nuanced and coherent system of grammar. Provocative and recommended.