These studies show how people with mediocre window manager and that doesn't know how to manage their windows benefits from a second screen. That's not my case and I am pretty sure I could show that one monitor is the fastest and most productive environment. I am pretty sure that tiling window managers, clever keybindings that never makes you need to move from the home row, replacement of the mouse by a keyboard based solution and vimification of the desktop are faster on a single monitor, and that they are faster than normal desktop on several monitors.