I guess perceptual shifting is standard to some degree in theater (just the nature of sets changing, but also the way say in Shakespeare we have random ghosts and spirits appearing all the time) but the way it's used in this play is a lot more conceptually intricate, more like complex movies

I think it borrows from novels - it's basically a novelistic technique - but sort of depends on the rise of modernism in novels. So I'd say novels, including and post Moby-Dick and Alice in Wonderland/Through the Looking Glass.

But it was a feature in movies already by the early 40s, so it probably entered movies early. I'd argue this is what's going on through the first two reels in It's a Wonderful Life (1946).

And of course there's A Christmas Carol which is full of dreamy timeshifting. Book published 1843-4, first movie 1938.

I bet there are other examples than these seasonal ones, but for obvious reasons they come right to mind.

Try Thornton Wilder's play Our Town.

http://en.wikipedia.org/wiki/Expressionism#Drama

Common use starting in Europe in the early 1900's - Strindberg and Wedekind are the two that came to my mind. Miller, of course, used the influences, but created his own unique story/take on the style.

Geez, sorry, been so long since I shared a link.

that's interesting. thanks for the pointers.