The Effect of Orthographic Neighbourhood and Semantics on Lexical Processing in a Transparent Orthographic Language: A Pupilometry Study

A word’s neighborhood comprises orthographically similar words, yet neighborhood effects in transparent orthographies remain theoretically underspecified. We investigated how lexical status and orthographic distance modulate cognitive effort using pupil dilation during silent reading. Pupillary responses from thirty-four adults were analyzed using a combination of Linear Mixed-Effects models and Generalized Additive Mixed Models across real words (RWs), low-distance pseudowords (PWs), and high-distance nonwords (NWs). Results revealed a temporal hierarchy and a double dissociation between lexical and orthographic processing. Specifically, the lexicality effect (RW > PW) emerged early (1333–2667 ms), reflecting the sustained cognitive load of semantic integration and global activation once lexical access is achieved. In contrast, the orthographic neighborhood effect (PW > NW) appeared at a later stage (2152–2727 ms), manifesting as a delayed peak that reflects the intense lateral inhibition required to suppress competing lexical candidates in PWs. While RWs trigger faster but deeper semantic processing, PWs result in a delayed response reflecting the difficulty of resolving competition among orthographically similar forms. These dynamics refine neighborhood theories by demonstrating that pupillometry can dissociate early-stage semantic activation from late-stage inhibitory control driven by orthographic similarity.