(1) I ate all the chocolate, even though I shouldn't have done .

(2) I ate all the chocolate, even though I shouldn't have .

I particularly wonder if the American formulation is as jarring to British ears as theirs is to mine.

but

I ate all the chocolate

I shouldn't have (done)

eat

all the chocolate.

eat all the chocolate

(3) I shouldn't have [eaten all the chocolate].

Bit

(have)

pro-predicate

(4) I ate all the chocolate, but I shouldn't have eaten it.

it

all the chocolate

do

done

eat(en) all the chocolate.

pro-predicate

do

eat

support verbs

(5) I ate all the chocolate, but I shouldn't have done it. [ do= 'eat']



(6) I ate some chocolate, and Better Half did too. [ do = 'eat some chocolate']

do

do

American Speech

do

Have you sent Lynne any chocolate yet?

I have done.

I haven't done.

I will do.

I might have done.

I could do.

I could have done.

I should do.

I should have done.

(etc.)

Butters (1983 ["Syntactic change in British English propredicates" Journal of English Linguistics 16:1-6]) adds that pro- do was possible as long ago as Middle English although it was not common in England until about the 1920s in the written sources which have been examined. Butters also presents historical evidence suggesting that pro- do spread from subordinate clauses to main clauses in the early part of this century. Most dialects of present-day English, including American English, probably preserve the conservative forms in dependent clauses, as in the following example:

[...] I usually kinda take a back seat, which I know I shouldn't DO but...

do

which I know I shouldn't do

do

do

even though

shouldn't have (done)

do

(7) I usually take a back seat, even though I know I shouldn't do.

even though

which

do

do