Parafoveal processing of words and saccade computation during eye fixations in reading

Studied parafoveal word processing during eye fixations in reading to answer two questions: (a) Is the processing of parafoveally available words limited to the identification of beginning letters? (b) Does the parafoveal processing of words affect the following interword saccade? Reading afforded either no parafoveal preview, preview of beginning trigrams, preview of ending trigrams, or preview of the whole parafoveal word. Previews were controlled by replacing original letters either with X's or dissimilar letters. Preview benefits were larger for the whole word previews than for beginning or ending trigram previews. X-masks yielded preview benefits from intact beginning and ending trigrams but dissimilar letter masks yielded benefits from beginning trigrams only. Saccades were larger for whole word previews than for no previews. These results support Logogen-type models of word recognition and a model of saccade computation that posits a time-locked functional relation between the acquisition of parafoveal word information and the positioning of each fixation.     

Font size modulates saccade-target selection in Chinese reading

In alphabetic writing systems, saccade amplitude (a close correlate of reading speed) is independent of font size, presumably because an increase in the angular size of letters is compensated for by a decrease of visual acuity with eccentricity. We propose that this invariance may (also) be due to the presence of spaces between words, guiding the eyes across a large range of font sizes. Here, we test whether saccade amplitude is also invariant against manipulations of font size during reading Chinese, a character-based writing system without spaces as explicit word boundaries for saccade-target selection. In contrast to word-spaced alphabetic writing systems, saccade amplitude decreased significantly with increased font size, leading to an increase in the number of fixations at the beginning of words and in the number of refixations. These results are consistent with a model which assumes that word beginning (rather than word center) is the default saccade target if the length of the parafoveal word is not available.     

Effects of parafoveal word length and orthographic features on initial fixation landing positions in reading

Previous research has demonstrated that readers use word length and word boundary information in targeting saccades into upcoming words while reading. Previous studies have also revealed that the initial landing positions for fixations on words are affected by parafoveal processing. In the present study, we examined the effects of word length and orthographic legality on targeting saccades into parafoveal words. Long (8?C9 letters) and short (4?C5 letters) target words, which were matched on lexical frequency and initial letter trigram, were paired and embedded into identical sentence frames. The gaze-contingent boundary paradigm (Rayner, 1975) was used to manipulate the parafoveal information available to the reader before direct fixation on the target word. The parafoveal preview was either identical to the target word or was a visually similar nonword. The nonword previews contained orthographically legal or orthographically illegal initial letters. The results showed that orthographic preprocessing of the word to the right of fixation affected eye movement targeting, regardless of word length. Additionally, the lexical status of an upcoming saccade target in the parafovea generally did not influence preprocessing.     

Semantic codes are not used in integrating information across eye fixations in reading: Evidence from fluent Spanish-English bilinguals

The question of whether meaning can be extracted from unidentified parafoveal words was examined using fluent Spanish-English bilinguals. In Experiment 1, subjects fixated on a central cross, and a preview word was presented to the right of fixation in parafoveal vision. During the saccade to the parafoveal preview word, the preview was replaced by the target word, which the subject was required to name. In Experiment 2, subjects read sentences containing the target word, and, as in the naming task, a preview word was replaced by the target word when the subject’s saccade crossed a boundary location. In both experiments, preview words were identical to the target word, translations, orthographic controls for the translations, or unrelated words in the opposite language. In both experiments, the preview benefit from the translation conditions was no greater than would be predicted by the orthographic similarity of the preview to the target. Hence, the data indicated that subjects obtained no useful semantic information from words seen parafoveally that enabled them to identify them more quickly on the subsequent fixation.     

Direct lexical control of eye movements in reading: evidence from a survival analysis of fixation durations

Participants' eye movements were monitored in an experiment that manipulated the frequency of target words (high vs. low) as well as their availability for parafoveal processing during fixations on the pre-target word (valid vs. invalid preview). The influence of the word-frequency by preview validity manipulation on the distributions of first fixation duration was examined by using ex-Gaussian fitting as well as a novel survival analysis technique which provided precise estimates of the timing of the first discernible influence of word frequency on first fixation duration. Using this technique, we found a significant influence of word frequency on fixation duration in normal reading (valid preview) as early as 145ms from the start of fixation. We also demonstrated an equally rapid non-lexical influence on first fixation duration as a function of initial landing position (location) on target words. The time-course of frequency effects, but not location effects was strongly influenced by preview validity, demonstrating the crucial role of parafoveal processing in enabling direct lexical control of reading fixation times. Implications for models of eye-movement control are discussed.     

副中央凹中字N+2的预视对汉语阅读眼跳目标选择影响的眼动研究

采用边界范式, 在副中央凹呈现一个双字词或两个单字词, 操纵字N+2的预视(目标预视和假字预视), 来考察副中央凹中词汇特征是否影响读者随后的眼跳长度及注视位置。结果发现, 读者能够获得字N+2的预视; 双字词与两个单字词条件下注视位置没有显著地差异; 当副中央凹中为双字词时, 字N+2为目标预视时随后的眼跳长度显著地长于假字预视条件, 随后的注视位置距离词首更远; 当副中央凹中为两个单字词时, 两种预视条件下随后的眼跳长度及注视位置没有显著的差异。本研究结果提示：在汉语阅读中, 读者能够对字N+2进行预视加工, 这种加工的影响只发生在当副中央凹中为双字词时。     

How preview space/time translates into preview cost/benefit for fixation durations during reading

Eye-movement control during reading depends on foveal and parafoveal information. If the parafoveal preview of the next word is suppressed, reading is less efficient. A linear mixed model (LMM) reanalysis of McDonald (2006) confirmed his observation that preview benefit may be limited to parafoveal words that have been selected as the saccade target. Going beyond the original analyses, in the same LMM, we examined how the preview effect (i.e., the difference in single-fixation duration, SFD, between random-letter and identical preview) depends on the gaze duration on the pretarget word and on the amplitude of the saccade moving the eye onto the target word. There were two key results: (a) The shorter the saccade amplitude (i.e., the larger preview space), the shorter a subsequent SFD with an identical preview; this association was not observed with a random-letter preview. (b) However, the longer the gaze duration on the pretarget word, the longer the subsequent SFD on the target, with the difference between random-letter string and identical previews increasing with preview time. A third pattern—increasing cost of a random-letter string in the parafovea associated with shorter saccade amplitudes—was observed for target gaze durations. Thus, LMMs revealed that preview effects, which are typically summarized under “preview benefit”, are a complex mixture of preview cost and preview benefit and vary with preview space and preview time. The consequence for reading is that parafoveal preview may not only facilitate, but also interfere with lexical access.     

Early parafoveal processing in reading Chinese sentences

The possibility that during Chinese reading information is extracted at the beginning of the current fixation was examined in this study. Twenty-four participants read for comprehension while their eye movements were being recorded. A pretarget-target two-character word pair was embedded in each sentence and target word visibility was manipulated in two time intervals (initial 140 ms or after 140 ms) during pretarget viewing. Substantial beginning- and end-of-fixation preview effects were observed together with beginning-of-fixation effects on the pretarget. Apparently parafoveal information at least at the character level can be extracted relatively early during ongoing fixations. Results are highly relevant for ongoing debates on spatially distributed linguistic processing and address fundamental questions about how the human mind solves the task of reading within the constraints of different writing systems.     

Parafoveal preview benefits during silent and oral reading: Testing the parafoveal information extraction hypothesis

The preview of a parafoveally visible word conveys benefits when it is subsequently fixated. The current study examined whether these benefits are determined by the effectiveness of parafoveal information extraction, as implied by current models of eye movement control during reading, or by the effectiveness with which extracted information is integrated when a previewed word is fixated. For this, the boundary technique was used to manipulate the extent to which parafoveal information could be extracted, and text was read silently or orally. Consistent with prior work, a parafoveal target word preview conveyed fewer benefits when less parafoveal information could be extracted, target viewing durations were longer during oral than during silent reading, and the two factors interacted in the target fixation data, with smaller preview benefits during oral than during silent reading. Survival analyses indicated that this occurred because parafoveal information use occurred at later point in time during oral reading. Diminished opportunity for parafoveal information extraction also diminished target skipping rate, and it resulted in smaller saccades to target words, but these effects were not influenced by reading mode. Parafoveally extracted information was thus used less effectively during oral reading only when it involved the integration of parafoveally extracted information during subsequent target viewing. The dissociation of extraction from integration challenges current models of eye movement control.     

眼跳发起位置对预视效应的影响

本文试图用实验的方法，通过调整目标词在句子中的位置，操纵目标词上注视点的眼跳发起位置，考察该变量对预视效应的影响。主要结果发现，和目标词上注视点的眼跳发起距离近的条件相比，眼跳发起距离远时凝视时间和回视路径时间的预视效应更大；但对数据的进一步分析表明这是一种阻碍效应。虽然“预视效益”这个词常用来代表预视加工，它实质包含了预视促进和阻碍两种不同的加工。本研究的结果有助于大家理解这两种不同性质的加工及其可能的影响因素。     

Integrating information across eye fixations in reading: the role of letter and word units

Eye movements and eye fixations were recorded to study the integration of letter/word information across interword fixations in reading. Two hypotheses were examined. One hypothesis posits that readers obtain effective information from the beginning two or three letters of a parafoveal word. This information facilitates the recognition of the word when it is being fixated. The alternative posits that effective information is obtained from the complete parafoveal word. The results of the present study showed faster reading rates when parafoveal previews comprised complete words than when they comprised beginning letters alone. Furthermore, the usability of parafoveally available partial word information from beginning and ending letters was not affected by small variations in retinal eccentricity. Both findings were taken as evidence that readers gain useful information from all letters of the parafoveally available word and that whole word information, rather than specific letter information, is integrated across interword fixations in reading.     

Parafoveal processing in word recognition

Two experiments investigated the degree to which properties of a word presented in the parafovea influenced the time to process a word undergoing concurrent foveal inspection. In Experiment 1, subjects viewed a set of five-letter words at a fixed point, with words in parafoveal vision varying in length, word frequency, and both the type and token frequency of occurrence of their initial three letters. The results showed that the frequency of the target and the type frequency of its initial letters influenced foveal fixation time. In Experiment 2, subjects executed a sequence of saccades before initial fixation on the experimental items. Under these circumstances, fixation time was shorter overall. Lexical properties of parafoveal words had no effect on foveal processing, but the length and the type frequency of their initial letters exerted a strong influence. Parafoveal-on-foveal effects of this form are incompatible with models of reading in which attention is allocated sequentially to successive words. The data are more consistent with the proposition that foveal and parafoveal processing occurs in parallel, with processing distributed over a region larger than a single word. Subsidiary analyses showed little influence of any of the manipulated variables on saccade extent.     

An anatomically constrained, stochastic model of eye movement control in reading

This article presents SERIF, a new model of eye movement control in reading that integrates an established stochastic model of saccade latencies (LATER; R. H. S. Carpenter, 1981) with a fundamental anatomical constraint on reading: the vertically split fovea and the initial projection of information in either visual field to the contralateral hemisphere. The novel features of the model are its simulation of saccade latencies as a race between two stochastic rise-to-threshold LATER units and its probabilistic selection of the target for the next saccade. The model generates simulated eye movement behavior that exhibits important characteristics of actual eye movements made during reading; specifically, simulations produce realistic saccade target distributions and replicate a number of critical reading phenomena, including the effects of word frequency on fixation durations, the inverted optimal viewing position effect, the trade-off between first and second fixation durations of refixated words, and the dependence of parafoveal preview benefit on eccentricity.     

The effect of preview eccentricity in a lexical decision task

We report lexical decision experiments in which eye movements and lexical decision time were analysed. The results show that nonwords produced more fixation than words, and that the time to make a lexical decision was also greater for nonwords. Further, a preview of the stimulus was presented on some occasions either at fixation or peripherally. When the presentation was peripheral the number of refixations and lexical decision times were reduced. Parafoveal previews of words also reduced word length effects on refixations and lexical decision time. These effects decreased (for nonwords) when the case of the letters was changed in the preview. These results are compatible with the idea that the peripheral preview benefit derives from word visual structure in addition to information about word length, word envelope, and single letter identities.     

Eye Movement Control During Reading: Foveal Load and Parafoveal Processing

We tested theories of eye movement control in reading by looking at parafoveal processing. According to attention-processing theories, attention shifts towards word n+1 only when processing of the fixated word n is finished, so that attended parafoveal processing does not start until the programming of the saccade programming to word n+1 is initiated (Henderson & Ferreira, 1990; Morrison, 1984), or even later when the processing of word n takes too long (Henderson & Ferreira, 1990). Parafoveal preview benefit should be constant whatever the foveal processing load (Morrison, 1984), or should decrease when processing word n outlasts an eye movement programming deadline (Henderson & Ferreira, 1990). By manipulating the frequency and length of the foveal word n and the visibility of the parafoveal word n+1 , we replicated the finding that the parafoveal preview benefit is smaller with a low-frequency word in foveal vision. Detailed analyses, however, showed that the eye movement programming deadline hypothesis could not account for this finding which was due not to cases where the low-frequency words n had received a long fixation, but to cases of a short fixations less than 240 msec. In addition, there was a spill-over effect of word n to word n+1 , and there was an element of parallel processing of both words. The results are more in line with parallel processing limited by the extent to which the parafoveal word processing on fixation n can be combined with the foveal word processing on fixation n+1 .     

Eye movements when reading transposed text: the importance of word-beginning letters

Participants' eye movements were recorded as they read sentences with words containing transposed adjacent letters. Transpositions were either external (e.g., problme, rpoblem) or internal (e.g., porblem, probelm) and at either the beginning (e.g., rpoblem, porblem) or end (e.g., problme, probelm) of words. The results showed disruption for words with transposed letters compared to the normal baseline condition, and the greatest disruption was observed for word-initial transpositions. In Experiment 1, transpositions within low frequency words led to longer reading times than when letters were transposed within high frequency words. Experiment 2 demonstrated that the position of word-initial letters is most critical even when parafoveal preview of words to the right of fixation is unavailable. The findings have important implications for the roles of different letter positions in word recognition and the effects of parafoveal preview on word recognition processes.     

The acquisition of parafoveal word information in reading

A somewhat counterintuitive finding has emerged from experiments that restrict the "window" of visual information available on a fixation during reading: fixation duration increases even though there is less information to process on a fixation. The two most likely explanations for this phenomenon are: (1) that the reader extracts abnormal information outside the window and this slows down processing; (2) that a restricted window does not allow a preview of a word before it is fixated, and hence identification of the word is slower when the word subsequently is fixated. In the present experiments, these two alternatives were tested. Conditions in which the size of the window alternated between fixations were compared with conditions in which the size of the window remained constant from fixation to fixation. This manipulation allowed us to separate effects due to restriction of the size of the window on the current fixation from preview benefits (which would be due to restriction of the size of the window on the prior fixation). Two experiments demonstrated clear beneficial effects on fixation duration due to receiving a preview of a word on the fixation prior to when it was fixated. In contrast, restriction of the size of the window had only marginal effects on the fixation on which that restriction occurred. In addition, a subsidiary analysis suggested that the benefit of previewing a word was influenced by its length; for short words, a preview primarily allowed the reader to skip the word more frequently, whereas for longer words, a preview primarily shortened the fixation time on the word when it was later fixated.     

Evidence for delayed parafoveal-on-foveal effects from word n+2 in reading

During reading information is acquired from word(s) beyond the word that is currently looked at. It is still an open question whether such parafoveal information can influence the current viewing of a word, and if so, whether such parafoveal-on-foveal effects are attributable to distributed processing or to mislocated fixations which occur when the eyes are directed at a parafoveal word but land on another word instead. In two display-change experiments, we orthogonally manipulated the preview and target difficulty of word n+2 to investigate the role of mislocated fixations on the previous word n+1. When the eyes left word n, an easy or difficult word n+2 preview was replaced by an easy or difficult n+2 target word. In Experiment 1, n+2 processing difficulty was manipulated by means of word frequency (i.e., easy high-frequency vs. difficult low-frequency word n+2). In Experiment 2, we varied the visual familiarity of word n+2 (i.e., easy lower-case vs. difficult alternating-case writing). Fixations on the short word n+1, which were likely to be mislocated, were nevertheless not influenced by the difficulty of the adjacent word n+2, the hypothesized target of the mislocated fixation. Instead word n+1 was influenced by the preview difficulty of word n+2, representing a delayed parafoveal-on-foveal effect. The results challenge the mislocated-fixation hypothesis as an explanation of parafoveal-on-foveal effects and provide new insight into the complex spatial and temporal effect structure of processing inside the perceptual span during reading.     

Is emotional content obtained from parafoveal words during reading? An eye movement analysis

An eye-movement-contingent display change technique was employed to study whether adult readers extract semantic information from parafoveal words during reading. Three types of parafoveal preview conditions were contrasted: an emotional word, a neutral word, and an identical word condition. To have a maximally effective parafoveal manipulation, high-arousal emotional words (sex- and threat-related and curse words) were used as parafoveal previews. Readers' eye fixation patterns around the target word revealed no evidence for parafoveal semantic processing. Furthermore, the pupil size showed no signs for an emotional response triggered by an emotional word previewed parafoveally. These results are consistent with the view that, as a rule, only the fixated word is processed to a semantic level during reading.