The New York Times ran this article in its "Fashion and Style" section on the anxiety that can be caused by the "typing awareness indicator"- that little gray bubble with the ellipses that pops up on your iPhone while the person on the other end of your text message is writing a response. Although this article does not describe an experiment, it is such a rich topic for experimentation!
Read the article from the New York Times here: Bubbles Carry a Lot of Weight