Does Extra Interletter Spacing Help Text Reading in Skilled Adult Readers?

A number of experiments have shown that, in skilled adult readers, a small increase in interletter spacing speeds up the process of visual word recognition relative to the default settings (i.e., judge faster than judge). The goal of the present experiment was to examine whether this effect can be generalized to a more ecological scenario: text reading. Each participant read two stories (367 words each) taken from a standardized reading test. The stories were presented with the standard interletter spacing or with a small increase in interletter spacing (+1.2 points to default) in a within-subject design. An eyetracker was used to register the participants' eye movements. Comprehension scores were also examined. Results showed that, on average, fixation durations were shorter while reading the text with extra spacing than while reading the text with the default settings (237 vs. 245 ms, respectively; eta(2) = .41, p = .01). However, the number of fixations (while nonsignificant) was slightly higher in the text with extra spacing than in the text with the default spacing, and cancelled out the effect of interletter spacing in total reading times (F < 1). Comprehension scores were similar in the two spacing conditions (F < 1). Thus, at least for skilled adult readers, interletter spacing does not seem to play a consistently facilitative role during text reading.