Malik, S., Findlater, L. (August 2013)
Non-alphanumeric symbols are rarely considered in text input research even though some punctuation is more frequent than the least common English letters. In this paper, we first evaluate punctuation frequency in two contrasting sources (Twitter and Google N-Grams). We then present a controlled study to compare existing techniques for ten-finger punctuation input on touchscreens, particularly looking at the cost of switching to and from punctuation input mode: (1) a status quo keyboard, which provides an alternate keyboard layer with punctuation symbols, and (2) an approach where users draw punctuation symbols atop the Qwerty keyboard itself . Our findings underscore the importance of considering punctuation input in keyboard design and highlight the cost of mode-switching to enter punctuation marks.