Exploring three types of perceptual span during silent reading in Russian

Word length span, letter feature span, and letter identity span are typically grouped under the umbrella term "perceptual span", although they reflect different types of processing. This study aimed to differentiate and estimate these spans in Russian-speaking adults. Additionally, we compared reading on LED and CRT monitors. In four experiments with a moving window paradigm, young adults read sentences in three masked conditions, where all letters except for three letters to the left and 12, 14, or 16 letters to the right of the fixation point were replaced with a mask, and a control condition. In Experiment 1, which explored word length span, all letters outside the window, including spaces, were replaced with Xs. In Experiments 2 and 3, which explored letter feature span, letters were replaced with Xs, but the spaces were preserved. In Experiment 4, which explored letter identity span, we substituted letters outside the window with visually similar ones. Experiments 1 and 2 were conducted on an LED monitor, while Experiments 3 and 4 were conducted on a CRT monitor. Our results showed that parafoveal letter replacement and spacing affected saccade targeting and slowed down reading rate, which was highest in word length span and lowest in letter identity span. These effects might be attributed to the leftward boundary: we found that three letters to the left of fixation are not sufficient for undisturbed reading in Russian-speaking adults.