Psychology of Computer Use: XXI. Effects of Text-Justification on Time to Read and Detect Typographical Errors from Crt-Displayed Text

Abstract

Although justified text (straight right margin) is generally preferred over unjustified text (ragged right margin), and most word-processing packages offer some type of justification option, justified text may degrade readability. Ninety-six university students participated in a study that examined the effects of text-justification on reading-rime and error-detection time when text was presented on a CRT display. Four justification conditions were compared: (a) even-gap justification (small spaces inserted proportionally between words), (b) fixed-spacing justification (a varying number of whole spaces inserted between words resulting in noticeable gaps), (c) unjustified text, and (d) unjustified text with varying numbers of spaces separating words. Analyses showed that text-justification had no effect on reading-time. However, error-detection time was faster with even-gap justification than in all other conditions and was faster with fixed-spacing justification and unjustified text than with unjustified text with varying numbers of interword spaces. The results were discussed in terms of the “positional uncertainty hypothesis,” i.e., the greater the uncertainty about the position of the next word, the greater the time to scan the text for errors.