Why does removing inter-word spaces produce reading deficits? The role of parafoveal processing.

To examine the role of inter-word spaces during reading, we used a gaze-contingent boundary paradigm to manipulate parafoveal preview (i.e., valid vs. invalid preview) in a normal text condition that contained spaces (e.g., "John decided to sell the table") and in an unsegmented text condition that contained random numbers instead of spaces (e.g.,"John4decided8to5sell9the7table"). Preview effects on mean first-fixation durations were larger for normal than unsegmented text conditions, and survival analyses revealed a delay in the onset of both preview validity and word-frequency effects on first-fixation durations for unsegmented relative to normal text. Taken together with simulations that were conducted using the E-Z Reader model, the present findings indicated that unsegmented text deficits reflect disruptions to both parafoveal processing and lexical processing. We discuss the implications of our results for models of eye-movement control.