Semantic parafoveal processing in natural reading: Insight from fixation-related potentials & eye movements

Parafoveal and foveal N400 effects in natural reading: A timeline of semantic processing from fixation-related potentials

The depth at which parafoveal words are processed during reading is an ongoing topic of debate. Recent studies using RSVP-with-flanker paradigms have shown that implausible words within sentences elicit an N400 component while they are still in parafoveal vision, suggesting that the semantics of parafoveal words can be accessed to rapidly update the sentence representation. To study this effect in natural reading, we combined the coregistration of eye movements and EEG with the deconvolution modeling of fixation-related potentials (FRPs) to test whether semantic plausibility is processed parafoveally during Chinese sentence reading. For one target word per sentence, both its parafoveal and foveal plausibility were orthogonally manipulated using the boundary paradigm. Consistent with previous eye movement studies, we observed a delayed effect of parafoveal plausibility on fixation durations that only emerged on the foveal word. Crucially, in FRPs aligned to the pretarget fixation, a clear N400 effect emerged already based on parafoveal plausibility, with more negative voltages for implausible previews. Once participants fixated the target, we again observed an N400 effect of foveal plausibility. Interestingly, this foveal N400 was absent whenever the preview had been implausible, indicating that when a word's (im)plausibility is already processed in parafoveal vision, this information is not revised anymore upon direct fixation. Implausible words also elicited a late positive component (LPC), but exclusively when in foveal vision. Our results not only provide convergent neural and behavioral evidence for the parafoveal uptake of semantic information, but also indicate different contributions of parafoveal versus foveal information toward higher level sentence processing.

Altered Eye Movements During Reading With Simulated Central and Peripheral Visual Field Defects

Purpose

Although foveal vision provides fine spatial information, parafoveal and peripheral vision are also known to be important for efficient reading behaviors. Here we systematically investigate how different types and sizes of visual field defects affect the way visual information is acquired via eye movements during reading.

Methods

Using gaze-contingent displays, simulated scotomas were induced in 24 adults with normal or corrected-to-normal vision during a reading task. The study design included peripheral and central scotomas of varying sizes (aperture or scotoma size of 2°, 4°, 6°, 8°, and 10°) and no-scotoma conditions. Eye movements (e.g., forward/backward saccades, fixations, microsaccades) were plotted as a function of either the aperture or scotoma size, and their relationships were characterized by the best fitting model.

Results

When the aperture size of the peripheral scotoma decreased below 6° (11 visible letters), there were significant decreases in saccade amplitude and velocity, as well as substantial increases in fixation duration and the number of fixations. Its dependency on the aperture size is best characterized by an exponential decay or growth function in log-linear coordinates. However, saccade amplitude and velocity, fixation duration, and forward/regressive saccades increased more or less linearly with increasing central scotoma size in log-linear coordinates.

Conclusions

Our results showed differential impacts of central and peripheral vision loss on reading behaviors while lending further support for the importance of foveal and parafoveal vision in reading. These apparently deviated oculomotor behaviors may in part reflect optimal reading strategies to compensate for the loss of visual information.

Semantic plausibility preferentially affects the semantic preview benefit in Chinese reading: evidence from an eye-movement study

Background

Numerous studies have confirmed that skilled readers can benefit from a semantically related preview word (i.e., semantic preview benefit, SPB), suggesting that readers can extract semantic information from the parafovea to achieve efficient reading. It is still under debate whether the occurrence of this benefit is because of the semantic association between the preview and target words or because of the contextual fit of the preview word in the sentence context.

Methods

Two independent factors, preview plausibility (preview plausible/implausible) and semantic relatedness (semantically related/unrelated), were manipulated, and we further strictly controlled for syntactic plausibility in the present study.

Results

The results showed that the first-pass reading times of the target words were significantly shorter in the plausible preview condition than in the implausible preview condition. However, the main effect of semantic relatedness was found only in the gaze duration measure.

Discussion

The pattern of results revealed that semantic plausibility affects the semantic preview benefit preferentially in Chinese reading, supporting the contextual fit account. Our findings have implications for a better understanding of parafoveal processing and provide empirical support for the eye-movement control model.

Parafoveal preview benefit in a conflicting sentential context: Evidence from ERPs

In natural reading, the reader's processing of a word starts when the word is located in parafoveal vision. Relative to a situation with an invalid preview, fixations are significantly shorter after a fully valid, identical preview. Although research on the identity preview benefit has been ongoing for more than 40 years, the mechanism of this preview benefit, the level of lexical processing it occurs, and its relationship to the sentential context remain unclear. This study employed EEG brain component analysis technology to address these questions in Chinese sentence reading. We manipulated the sentential context to make the target word plausible or not plausible with the sentence and manipulated the target word present or not present in preview. EEG results showed that the identity preview benefit can affect not only the early preview positivity, reflecting the early orthographic processing of words, but also the N400 and LPC components, reflecting the late and in-depth semantic processing of words. Conflicting sentential context, in which the target word is implausible and cannot be integrated into the sentence, can interfere temporarily with these processes. These findings suggest that in the process of sentence reading, an identical preview word can promote the subsequent reading process at multiple levels, and its role is modulated by contextual information.

Parafoveal words can modulate sentence meaning: Electrophysiological evidence from an RSVP-with-flanker task

During natural reading, readers can take up some visual information from not-yet-fixated words to the right of the current fixation and it is well-established that this parafoveal preview facilitates the subsequent foveal processing of the word. However, the extraction and integration of word meaning from parafoveal words and their possible influence on the semantic content of the sentence are controversial. In the current study, we recorded event-related potentials (ERPs) in the RSVP-with-flankers paradigm to test whether and how updates of sentential meaning, based only on parafoveal information, may influence the subsequent foveal processing. In Chinese sentences, the congruency of parafoveal and foveal target words with the sentence was orthogonally manipulated. In contrast to previous research, we also controlled for potentially confounding effects of parafoveal-to-foveal repetition priming (identity preview effects) on the N400. Crucially, we found that the classic effect of foveal congruency on the N400 component only appeared when the word in preview had been congruent with sentence meaning; in contrast, there was no N400 as a function of foveal incongruency when the preview word had also been incongruent. These results indicate that sentence meaning rapidly adapts to parafoveal preview, altering the semantic context for the subsequently fixated word. We also show that correct parafoveal preview generally attenuates the N400 once a word is fixated, regardless of congruency. Taken together, our findings underline the highly generative and adaptive framework of language comprehension.