When Layout Meets Syntax: The Role of Line Break Placement in Sentence Reading

Typographic features such as font type, character size, and spacing are well known to influence visual and cognitive processing during reading. By contrast, the effects of other typographic variables, including layout and line-break placement, remain comparatively underexplored. Notably, most printed materials are fully justified rather than left-aligned, and line breaks are therefore determined by spatial constraints rather than linguistic factors. This raises the question of whether line-break placement influences reading fluency. The present study investigates how line-break placement interacts with syntactic structure during reading, and whether alignment or misalignment between visual and syntactic segmentation affects reading fluency. Short sentences were presented on screen: in the aligned condition, breaks respected natural syntactic groupings; in the misaligned condition, they disrupted closely related constituents (e.g., noun phrases), creating a mismatch between visual segmentation and syntactic structure. Twenty-four university students read the sentences silently while sentence-level reading times were recorded. Comprehension questions ensured attentive reading. Results indicate that less predictable line breaks lead to longer reading times, particularly when they disrupt strong syntactic constituents. This pattern suggests increased processing costs due to disrupted parsing. Crucially, this effect emerges even in skilled adult readers under relatively naturalistic reading conditions. Moreover, it remains significant when controlling for sentence length and is observed both across participants and items. These findings highlight the role of typographic layout in reading and demonstrate that subtle formatting choices, such as line-break placement, can influence reading fluency, with important implications for the design of accessible texts, especially for readers with reading difficulties.