There are studies. Quite a few of them. (Score 1)

If you are truly interested, read Norbert Wiener's short and enjoyable book, Cybernetics: Or the Control and Communication in the Animal and the Machine. You will find an entire field and 60 year's worth of studies on interface efficiency (among other things). The people who designed fighter planes in WWII were quite concerned about readability, and this interest has not waned.