Return-sweeps in Reading: Processing Implications of Undersweep-Fixations

Models of eye movement control during reading focus on reading single lines of text. However, with multi-line texts, return-sweeps which bring fixation from the end of one line to the beginning of the next occur regularly and influence ~20% of all reading fixations. Our understanding of return sweeps is still limited. One common feature of return sweeps is the prevalence of oculomotor errors. Return sweeps, often initially under-shoot the start of the line. Corrective saccades then bring fixation closer to the line start. The fixation occurring between the undershoot and the corrective saccade (undersweep-fixation) has important theoretical implications for the serial nature of lexical processing during reading, as they occur on words ahead of the intended attentional target. Furthermore, since the attentional target of a return-sweep will lie far outside the parafovea during the prior fixation, it cannot be lexically pre-processed on the prior fixation. We explore the implications of undersweep-fixations for ongoing processing and models of eye movements during reading by analyzing two existing eye-movement data sets of multiline reading.