Reading Online Text: A Comparison of Four White Space Layouts
http://psychology.wichita.edu/surl/usabilitynews/62/whitespace.htm

Chaparro, Barbara S., J. Ryan Baker, A. Dawn Shaikh, Spring S. Hull and Laurie Brady
Usability News
2004

Abstract:

In this study, reading performance with four white space layouts was compared. Margins surrounding the text and leading (space between lines) were manipulated to generate the four white space conditions. Results show that the use of margins affected both reading speed and comprehension in that participants read the Margin text slower, but comprehended more than the No Margin text. Participants were also generally more satisfied with the text with margins. Leading was not shown to impact reading performance but did influence overall user preference.