Lower-level oculomotor deficits in schizophrenia during multi-line reading: Evidence from return-sweeps

Abstract

Reading fluency deficits in schizophrenia (Sz) have been attributed to dysfunction in both lower-level, oculomotor processing and higher-level, lexical processing, according to the 2-hit deficit model (Dias et al., 2021). Given that prior work examining reading deficits in readers with Sz has primarily focused on single-line and single-word reading tasks, eye-movements that are unique to passage reading, such as return-sweep saccades, have not yet been examined in Sz. Return-sweep saccades are large eye-movements that are made when readers move from the end of one line to the beginning of the next line during natural passage reading. Examining return-sweeps provides an opportunity to examine lower-level, oculomotor deficits during reading under circumstances when upcoming higher-level, lexical information is not available for visual processing because visual acuity constraints do not permit detailed lexical processing of line-initial words when return-sweeps are programmed. To examine the source of reading deficits in Sz, we analyzed an existing dataset (Dias et al., 2021) in which participants read multi-line passages with manipulations to line-spacing. Readers with Sz made significantly more return-sweep targeting errors followed by corrective saccades compared to healthy controls. Both groups showed similar effects of line spacing on return-sweep targeting accuracy, suggesting similar sensitivities to visual crowding during reading. Furthermore, the patterns of fixation durations in readers with Sz corroborates prior work indicating reduced parafoveal processing of upcoming words. Together, these findings suggest that lower-level visual and oculomotor dysfunction contribute to reading deficits in Sz, providing support for the 2-hit deficit model (Dias et al., 2021).