Typography and Readability
Wheildon provides useful statistics on how typography affects readability. The main question is whether readers prefer serif or sans serif typeface for body text.
Tradition has always favored serif type. Wheildon cites a 1926 study by the British Medical Council that concluded that the absence of serifs caused an "optical effect where the lines of type intruded into the letters, setting up a form of light vibration, which militated against comfortable reading" (56).
Wheildon came to the same conclusion through his own research, and advises editors to use serif typeface for the body text. He found that the majority of his subjects reported trouble maintaining their concentration when sans serif body text was used instead(57).
Headline typeface was another matter, however. According to Wheildon, sans serif ranked higher when readers were rating headlines, but the statistical difference was negligible. He advises that editors choose a headline typeface based on what is most suitable to the image of their publication.