Are Eye Movements and EEG on the Same Page?: A Coregistration Study on Parafoveal Preview and Lexical Frequency

published Online: September 15, 2022
Readers extract visual and linguistic information not only from fixated words but also upcoming parafoveal words to introduce new input efficiently into the language processing pipeline. The lexical frequency of upcoming words and similarity with subsequent foveal information both influence the amount of time people spend once they fixate the word foveally. However, it is unclear from eye movements alone the extent to which parafoveal word processing, and the integration of that word with foveally obtained information, continues after saccade plans have been initiated. To investigate the underlying neural processes involved in word recognition after saccade planning, we coregistered electroencephalogram (EEG) and eye movements during a gaze-contingent display change paradigm. We orthogonally manipulated the frequency of the parafoveal and foveal words and measured fixation related potentials (FRPs) upon foveal fixation. Eye movements showed primarily an effect of preview frequency, suggesting that saccade planning is based on the familiarity of the parafoveal input. FRPs, on the other hand, demonstrated a disruption in downstream processing when parafoveal and foveal input differed, but only when the parafoveal word was high frequency. These findings demonstrate that lexical processing continues after the eyes have moved away from a word and that eye movements and FRPs provide distinct but complementary accounts about oculomotor behavior and neural processing that cannot be obtained from either method in isolation. Furthermore, these findings put constraints on models of reading by suggesting that lexical processes that occur before an eye movement program is initiated are qualitatively different from those that occur afterward.