Increasingly in both spoken and written varieties of English, especially in America but not only, one hears/reads the subjective case pronoun form replacing the standard objective case form in coordinate constructions. For example, on May 24, 1993, the sentence “I’m picking you and I” emanated from the mouth of a commentator on the National Public Radio program “Morning Edition,” in a lame attempt at humor, admitting to the program’s host his inability to predict the winner of the doubles competition in the French Open Tennis Championships. This jarring solecism is more often to be found after prepositions, e. g., *between you and I, etc. The substitution of I for me here is what is usually called a hyperurbanism (hypercorrection), meaning the use of the wrong form as a result of the speaker’s wishing to sound educated. However, one can explore the possibility of there being a deeper reason for this substitution, and to propose a different interpretation, one that relies on an understanding of METANALYSIS or boundary shift.
First a short description of the grammatical facts. When grammatical government is involved, as it is in between you and I/me, the normal domain of the preposition extends to each constituent in the complement, as it does to the direct object of the verb in picking you and me. Thus whether there is a preposition preceding the coordinate phrase or not, the form of all constituents in the complement should be in the objective case. The second person pronoun you is syncretic; it does not differentiate the subjective from the objective form, but the first person does. Why do some speakers place the subjective form I in objective position?
The first thing to point out is the fact of a coordinate construction. We are dealing here not with a simple complement but with a compound. Even in nonstandard American English there are no attested instances of sentences like *He picks I or *She talks to I (although British dialects do have them). So the compound character of the complement is evidently a necessary precondition for the solecism.
Now, one property of a unit is its boundedness. In a compound unit, the boundaries envelop all of the constituents; otherwise the compound would lose its character as a unit. In other words, disregarding the conjunction, a coordinate phrase of the type you and I is bracketed [you and I] rather than [you] and [I]; it has only two major boundaries, at the two margins of the construction, rather than six minor boundaries––the number it would have if it were simply the additive product of two personal pronouns separated by a conjunction. In the solecistic construction, the individual constituents inside the boundaries that enclose the compound seem to be insulated from case government. They undergo no change, even while being syntactically liable to it, apparently because compounds of this type are analyzed by speakers who utter these solecisms as being unitary, undifferentiated gestalts. Such speakers ignore the internal noun phrase boundaries, assigning case only to the whole compound noun phrase. In standard American English, by contrast, the boundaries are observed, and each constituent receives its appropriate morphological inflection.
The grammatical solecism can thus be understood as the effect of boundaries being suppressed, specifically the minor boundaries around the pronouns. (This might also explain why solecisms like *to he and I are heard, but not *to him and I.)
Which is not to say that the boundaries on either side of the individual constituents cease to exist just because the coordinate construction has boundaries enclosing it. Not at all. Here we have an example of the variable strengths of linguistic boundaries. In the hierarchy of boundaries involved in the phrase at issue, the supervening compound boundary is the major or salient one, while the remaining minor ones are present but not germane.