Encoding multiple words simultaneously in reading is implausible

Towards a model of eye-movement control in Chinese reading

The Chinese writing system has several features that make it markedly different from the alphabetic systems that have most often been examined in reading research, including the fact that individual words consist of various uniformly sized, box-shaped characters whose boundaries are not clearly demarcated (e.g., by blank spaces). These features raise the question: How do readers of Chinese "know" where to move their eyes for the purpose of efficiently segmenting and/or identifying words? To answer this question, we used the E-Z Reader model of eye-movement control in reading to run an 'experiment' involving a series of simulations in which two saccade-targeting assumptions (i.e., directing the eyes towards default targets vs. adjusting saccade length as a function of parafoveal processing difficulty) were factorially manipulated with three word-segmentation heuristics (i.e., ideal-observer knowledge of word boundaries vs. probabilistic guessing vs. familiarity-based segmentation) to examine which combination of assumptions provide the best quantitative account of eye-movement control during the reading of Chinese. Based on these simulations, we conclude the best account is one in which readers use relative differences in the familiarity of groups of parafoveal characters to dynamically adjust the lengths of saccades in a manner that affords efficient word identification. We discuss the broader theoretical implications of these conclusions for models of Chinese reading and for models of reading more generally.

Investigating the crowding effect on letters and symbols in deaf adults

Reading requires the transformation of a complex array of visual features into sounds and meaning. For deaf signers who experience changes in visual attention and have little or no access to the sounds of the language they read, understanding the visual constraints underlying reading is crucial. This study aims to explore a fundamental aspect of visual perception intertwined with reading: the crowding effect. This effect manifests as the struggle to distinguish a target letter when surrounded by flanker letters. Through a two-alternative forced choice task, we assessed the recognition of letters and symbols presented in isolation or flanked by two or four characters, positioned either to the left or right of fixation. Our findings reveal that while deaf individuals exhibit higher accuracy in processing letters compared to symbols, their performance falls short of that of their hearing counterparts. Interestingly, despite their proficiency with letters, deaf individuals didn't demonstrate quicker letter identification, particularly in the most challenging scenario where letters were flanked by four characters. These outcomes imply the development of a specialized letter processing system among deaf individuals, albeit one that may subtly diverge from that of their hearing counterparts.

Severe processing capacity limits for sub-lexical features of letter strings

When reading, the visual system is confronted with many words simultaneously. How much of that information can a reader process at once? Previous studies demonstrated that low-level visual features of multiple words are processed in parallel, but lexical attributes are processed serially, for one word at a time. This implies that an internal bottleneck lies somewhere between early visual and lexical analysis. We used a dual-task behavioral paradigm to investigate whether this bottleneck lies at the stage of letter recognition or phonological decoding. On each trial, two letter strings were flashed briefly, one above and one below fixation, and then masked. In the letter identification experiment, participants indicated whether a vowel was present in a particular letter string. In the phonological decoding experiment, participants indicated whether the letter string was pronounceable. We compared accuracy in a focused attention condition, in which participants judged only one of the two strings, with accuracy in a divided attention condition, in which participants judged both strings independently. In both experiments, the cost of dividing attention was so large that it supported a serial model: participants were able to process only one letter string per trial. Furthermore, we found a stimulus processing trade-off that is characteristic of serial processing: When participants judged one string correctly, they were less likely to judge the other string correctly. Therefore, the bottleneck that constrains word recognition under these conditions arises at a sub-lexical level, perhaps due to a limit on the efficiency of letter recognition.

The transposed-word effect provides no unequivocal evidence for parallel processing

Studies using a grammaticality decision task have revealed surprising flexibility in the processing of word order during sentence reading in both alphabetic and non-alphabetic scripts. Participants in these studies typically exhibit a transposed-word effect, in which they make more errors and slower correct responses for stimuli that contain a word transposition and are derived from grammatical as compared to ungrammatical base sentences. Some researchers have used this finding to argue that words are encoded in parallel during reading, such that multiple words can be processed simultaneously and might be recognised out of order. This contrasts with an alternative account of the reading process, which argues that words must be encoded serially, one at a time. We examined, in English, whether the transposed-word effect provides evidence for a parallel-processing account, employing the same grammaticality decision task used in previous research and display procedures that either allowed for parallel word encoding or permitted only the serial encoding of words. Our results replicate and extend recent findings by showing that relative word order can be processed flexibly even when parallel processing is not possible (i.e., within displays requiring serial word encoding). Accordingly, while the present findings provide further evidence for flexibility in the processing of relative word order during reading, they add to converging evidence that the transposed-word effect does not provide unequivocal evidence for a parallel-processing account of reading. We consider how the present findings may be accounted for by both serial and parallel accounts of word recognition in reading.

Parallel phonological processing of Chinese characters revealed by flankers tasks

An important and extensively researched question in the field of reading is whether readers can process multiple words in parallel. An unresolved issue regarding this question is whether the phonological information from foveal and parafoveal words can be processed in parallel, i.e., parallel phonological processing. The present study aims to investigate whether there is parallel phonological processing of Chinese characters. The original and the revised flankers tasks were applied. In both tasks, a foveal target character was presented in isolation in the no-flanker condition, flanked on both sides by a parafoveal homophone in the homophone-flanker condition, and by a non-homophonic character in the unrelated-flanker condition. Participants were instructed to fixate on the target characters and press two keys to indicate whether they knew the target characters (lexical vs. non-lexical). In the original flankers task, the stimuli were presented for 150 ms without a post-mask. In the revised flankers task, we set the stimulus exposure time (duration of the stimuli plus the blank interval between the stimuli and the post-mask) to each participant's lexical decision threshold to prevent participants from processing the target and flanker characters serially. In both tasks, reaction times to the lexical targets were significantly shorter in the homophone-flanker condition than in the unrelated-flanker condition, suggesting parallel phonological processing of Chinese characters. In the revised flankers task, accuracy rates to the lexical targets were significantly lower in the unrelated-flanker condition compared to the homophone-flanker condition, further supporting parallel phonological processing of Chinese characters. Moreover, reaction times to the lexical targets were the shortest in the no-flanker condition in both tasks, reflecting the attention distribution over both the target and flanker characters. The findings of this study provide valuable insights into the parallel processing mechanisms involved in reading.

Parallel word reading revealed by fixation-related brain potentials

During reading, the brain is confronted with many relevant objects at once. But does lexical processing occur for multiple words simultaneously? Cognitive science has yet to answer this prominent question. Recently it has been argued that the issue warrants supplementing the field's traditional toolbox (response times, eye-tracking) with neuroscientific techniques (EEG, fMRI). Indeed, according to the OB1-reader model, upcoming words need not impact oculomotor behavior per se, but parallel processing of these words must nonetheless be reflected in neural activity. Here we combined eye-tracking with EEG, time-locking the neural window of interest to the fixation on target words in sentence reading. During these fixations, we manipulated the identity of the subsequent word so that it posed either a syntactically legal or illegal continuation of the sentence. In line with previous research, oculomotor measures were unaffected. Yet, syntax impacted brain potentials as early as 100 ms after the target fixation onset. Given the EEG literature on syntax processing, the presently observed timings suggest parallel word reading. We reckon that parallel word processing typifies reading, and that OB1-reader offers a good platform for theorizing about the reading brain.

Transposed-word effects when reading serially

When asked to decide if an ungrammatical sequence of words is grammatically correct or not readers find it more difficult to do so (longer response times (RTs) and more errors) if the ungrammatical sequence is created by transposing two words from a correct sentence (e.g., the white was cat big) compared with a set of matched ungrammatical sequences for which transposing any two words could not produce a correct sentence (e.g., the white was cat slowly). Here, we provide a further exploration of transposed-word effects while imposing serial reading by using rapid serial visual presentation (RSVP) in Experiments 1 (respond at the end of the sequence) and 2 (respond as soon as possible-which could be during the sequence). Crucially, in Experiment 3 we compared performance under serial RSVP conditions with parallel presentation of the same stimuli for the same total duration and with the same group of participants. We found robust transposed-word effects in the RSVP conditions tested in all experiments, but only in error rates and not in RTs. This contrasts with the effects found in both errors and RTs in our prior work using parallel presentation, as well as the parallel presentation conditions tested in Experiment 3. We provide a tentative account of why, under conditions that impose a serial word-by-word reading strategy, transposed-word effects are only seen in error rates and not in RTs.

Sequential versus simultaneous presentation of memoranda in verbal working memory: (How) does it matter?

To-be-memorized information in verbal working memory (WM) can be presented sequentially, like in oral language, and simultaneously, like in written language. Few studies have addressed the importance and implications for verbal WM processing of these two presentation modes. While sequential presentation may favor discrete, temporal encoding processes, simultaneous presentation may favor spatial encoding processes. We compared immediate serial recall tasks for sequential versus simultaneous word list presentation with a specific focus on serial position curves of recall performance, transposition gradients, and the nature of serial order errors. First, we observed higher recall performance in the simultaneous compared to the sequential conditions, with a particularly large effect at end-of-list items. Moreover, results showed more transposition errors between non-adjacent items for the sequential condition, as well as more omission errors especially for start-of-list items. This observation can be explained in terms of differences in refreshing opportunities for start-of-list items during encoding between conditions. This study shows that the presentation mode of sequential material can have a significant impact on verbal WM performance, with an advantage for simultaneous encoding of sequence information.

An oscillatory pipelining mechanism supporting previewing during visual exploration and reading

Humans have a remarkable ability to efficiently explore visual scenes and text using eye movements. Humans typically make eye movements (saccades) every ~250 ms. Since saccade initiation and execution take 100 ms, this leaves only ~150 ms to recognize the fixated object (or word) while simultaneously previewing candidates for the next saccade goal. We propose a pipelining mechanism where serial processing occurs within a specific brain region, whereas parallel processing occurs across different brain regions. The mechanism is timed by alpha oscillations that coordinate the saccades, visual recognition, and previewing in the cortical hierarchy. Consequently, the neuronal mechanism supporting natural vision and saccades must be studied in unison to uncover the brain mechanisms supporting visual exploration and reading.

A transposed-word effect across space and time: Evidence from Chinese

A compelling account of the reading process holds that words must be encoded serially, and so recognized strictly one at a time in the order they are encountered. However, this view has been challenged recently, based on evidence showing that readers sometimes fail to notice when adjacent words appear in ungrammatical order. This is argued to show that words are actually encoded in parallel, so that multiple words are processed simultaneously and therefore might be recognized out of order. We tested this account in an experiment in Chinese with 112 skilled readers, employing methods used previously to demonstrate flexible word order processing, and display techniques that allowed or disallowed the parallel encoding of words. The results provided evidence for flexible word order processing even when words must be encoded serially. Accordingly, while word order can be processed flexibly during reading, this need not entail that words are encoded in parallel.

Neural evidence for lexical parafoveal processing

In spite of the reduced visual acuity, parafoveal information plays an important role in natural reading. However, competing models on reading disagree on whether words are previewed parafoveally at the lexical level. We find neural evidence for lexical parafoveal processing by combining a rapid invisible frequency tagging (RIFT) approach with magnetoencephalography (MEG) and eye-tracking. In a silent reading task, target words are tagged (flickered) subliminally at 60 Hz. The tagging responses measured when fixating on the pre-target word reflect parafoveal processing of the target word. We observe stronger tagging responses during pre-target fixations when followed by low compared with high lexical frequency targets. Moreover, this lexical parafoveal processing is associated with individual reading speed. Our findings suggest that reading unfolds in the fovea and parafovea simultaneously to support fluent reading.

Using eye tracking to investigate failure to notice word transpositions in reading

Previous research (Mirault, Snell, & Grainger, 2018) has demonstrated that subjects sometimes incorrectly judge an ungrammatical sentence as grammatical when it is created by the transposition of two words in a grammatical sentence (e.g., The white was cat big). Here we present two eye-tracking experiments designed to assess the prevalence of this phenomenon in a more natural reading task, and to explore theoretical explanations. Readers failed to notice transpositions at about the same rate as in Mirault et al. (2018). Failure to notice the transposition was more common when both words were short, and when readers' eyes skipped, rather than directly fixated, one of the two words. The status of the transposed words as open- or closed-class did not have a reliable effect. The transposed words caused disruption in the eye movement record only on trials when participants ultimately judged the sentence to be ungrammatical, not when they judged the sentence to be grammatical. We argue that the results are not entirely consistent with the account offered by Mirault et al. (2018), which attributes failure to notice transpositions to parallel processing of adjacent words, or with a late, post-perceptual rational inference account (Gibson, Bergen, & Piantadosi, 2013). We propose that word recognition is serial, but post-lexical integration of each word into its context may not be perfectly incremental.

The transposed-word effect revisited: the role of syntax in word position coding

Skilled readers may misinterpret “you that read wrong” for “you read that wrong”: a transposed-word effect. This relatively novel finding, which supports parallel word processing during sentence reading, is attributed to a combination of noisy bottom-up word position coding and top-down syntactic constraints. The present study focussed on the contribution of syntactic constraints in driving transposed-word effects. In a speeded grammatical decision experiment, two types of ungrammatical transposed-word sequences were compared, namely a transposition either across a syntactic phrase (“the have girls gone home”) or within a syntactic phrase (“the girls gone have home”). We found longer response times and lower accuracy rates for within-phrase transpositions than across-phrase transpositions, demonstrating a direct influence of syntactic structures on the transposed-word effect. We conclude that the assignment of words to positions in a sentence is guided by top-down syntactic constraints.

Letter and word identification in the fovea and parafovea

We investigated the extent to which accuracy in word identification in foveal and parafoveal vision is determined by variations in the visibility of the component letters of words. To do so we measured word identification accuracy in displays of three three-letter words, one on fixation and the others to the left and right of the central word. We also measured accuracy in identifying the component letters of these words when presented at the same location in a context of three three-letter nonword sequences. In the word identification block, accuracy was highest for central targets and significantly greater for words to the right compared with words to the left. In the letter identification block, we found an extended W-shaped function across all nine letters, with greatest accuracy for the three central letters and for the first and last letter in the complete sequence. Further analyses revealed significant correlations between average letter identification per nonword position and word identification at the corresponding position. We conclude that letters are processed in parallel across a sequence of three three-letter words, hence enabling parallel word identification when letter identification accuracy is high enough.

An ERP investigation of transposed-word effects in same-different matching

Can several words be read in parallel, and if so, how is information about word order encoded under such circumstances? Here we focused on the bottom-up mechanisms involved in word-order encoding under the hypothesis of parallel word processing. We recorded EEG while participants performed a visual same-different matching task with sequences of five words (reference sequence followed by a target sequence each presented for 400 ms). The reference sequence could be grammatically correct or an ungrammatical scrambling of the same words (e.g., he wants these green apples/green wants these he apples). Target sequences for 'different' responses were created by either transposing two words in the reference (e.g., he these wants green apples/green these wants he apples), or by changing two words (e.g., he talks their green apples/green talks their he apples). Different responses were harder to make in the transposition condition, and this transposed-word effect started to emerge around 250 ms post-target onset. The transposed-word effect was first seen on an early onsetting N400 component, with reduced amplitudes (i.e., less negative ERPs) in the transposed condition relative to a two-word replacement condition. A later transposed-word effect was seen on a more temporally widespread positive-going component. Converging behavioral and EEG results showed no effects of reference grammaticality on 'different' responses nor an interaction with transposed-word effects. Our results point to the noisy, bottom-up association of word identities to spatiotopic locations as one means of encoding word order information, and one key source of transposed-word effects.

Attention extends beyond single words in beginning readers

A common notion is that during the first stages of learning to read, attention is narrowly focused so as to encompass only a single or a few letters. In skilled adult readers, however, attention extends beyond single words. The latter is evidenced by faster recognition of words that have many letters in common with surrounding words, along with correlations between such integration effects and measures of attention. These premises suggest that the distribution of attention gradually increases as a function of reading skill, and that this progression can be mapped by measuring spatial integration effects across the course of reading development. The latter was undertaken in the present study, in which we employed the flanker paradigm combined with the lexical decision task. Children in grades 1-6 (N = 113) were shown central target words flanked by various types of orthographically related and unrelated flanking stimuli. Against expectations, significant effects of flanker relatedness on word recognition speed were found in the youngest children, and this effect was not modulated by reading age. Our results challenge the notion that attention is focused on single letters in beginning readers, and instead suggest that, from the earliest stages of reading development, orthographic processing can extend beyond single words.

On the noisy spatiotopic encoding of word positions during reading: Evidence from the change-detection task

The present study builds on our prior work showing evidence for noisy word-position coding in an immediate same-different matching task. In that research, participants found it harder to judge that two successive brief presentations of five-word sequences were different when the difference was caused by transposing two adjacent words compared with different word replacements – a transposition effect. Here we used the change-detection task with a 1-s delay introduced between sequences – a task thought to tap into visual short-term memory. Concurrent articulation was used to limit the contribution of active rehearsal. We used standard response-time (RT) and error-rate analyses plus signal detection theory (SDT) measures of discriminability (d’) and bias (c). We compared the transposition effects for ungrammatical word sequences and nonword sequences observed with these different measures. Although there was some evidence for transposition effects with nonwords, the effects were much larger with word sequences. These findings provide further support for the hypothesized noisy assignment of word identities to spatiotopic locations along a line of text during reading.

A transposed-word effect in Chinese reading

Studies using a grammaticality decision task suggest surprising flexibility in the processing of the relative order of words in sentences when reading alphabetic scripts like French. In these studies, participants made rapid grammaticality decisions for ungrammatical stimuli created by transposing two adjacent words in either a grammatical or an ungrammatical base sentence, which were intermixed with equal numbers of grammatically correct stimuli. The key finding was that participants made more errors and were slower to reject transposed-word stimuli created from grammatical than ungrammatical base sentences. This suggested that flexibility in the processing of word order allowed participants to access representations of the base grammatical sentences, interfering with their decisions to correctly reject transposed-word stimuli. With the present research, we investigated if a similar transposed-word effect is observed for a non-alphabetic script (Chinese) that uses few grammatical markers and primarily conveys grammatical structure via word order. Such scripts may require stricter processing of word order during reading and so provide a strong test of the cross-linguistic generality of the transposed-word effect. We report three experiments using the same design and procedure as previous research, while varying the length of the transposed words across experiments. In all three experiments, participants made more errors and were slower to reject transposed-word stimuli derived from grammatical than ungrammatical base sentences. This replicates previous findings with alphabetic scripts and provides novel evidence for a transposed-word effect in Chinese reading. We consider the implications for models of reading in alphabetic and non-alphabetic scripts.

Visual word recognition: Evidence for a serial bottleneck in lexical access

Reading is a demanding task, constrained by inherent processing capacity limits. Do those capacity limits allow for multiple words to be recognized in parallel? In a recent study, we measured semantic categorization accuracy for nouns presented in pairs. The words were replaced by post-masks after an interval that was set to each subject's threshold, such that with focused attention they could categorize one word with ~80% accuracy. When subjects tried to divide attention between both words, their accuracy was so impaired that it supported a serial processing model: on each trial, subjects could categorize one word but had to guess about the other. In the experiments reported here, we investigated how our previous result generalizes across two tasks that require lexical access but vary in the depth of semantic processing (semantic categorization and lexical decision), and across different masking stimuli, word lengths, lexical frequencies and visual field positions. In all cases, the serial processing model was supported by two effects: (1) a sufficiently large accuracy deficit with divided compared to focused attention; and (2) a trial-by-trial stimulus processing tradeoff, meaning that the response to one word was more likely to be correct if the response to the other was incorrect. However, when the task was to detect colored letters, neither of those effects occurred, even though the post-masks limited accuracy in the same way. Altogether, the results are consistent with the hypothesis that visual processing of words is parallel but lexical access is serial.

Eye Movements and Fixation-Related Potentials in Reading: A Review

The present review is addressed to researchers in the field of reading and psycholinguistics who are both familiar with and new to co-registration research of eye movements (EMs) and fixation related-potentials (FRPs) in reading. At the outset, we consider a conundrum relating to timing discrepancies between EM and event related potential (ERP) effects. We then consider the extent to which the co-registration approach might allow us to overcome this and thereby discriminate between formal theoretical and computational accounts of reading. We then describe three phases of co-registration research before evaluating the existing body of such research in reading. The current, ongoing phase of co-registration research is presented in comprehensive tables which provide a detailed summary of the existing findings. The thorough appraisal of the published studies allows us to engage with issues such as the reliability of FRP components as correlates of cognitive processing in reading and the advantages of analysing both data streams (i.e., EMs and FRPs) simultaneously relative to each alone, as well as the current, and limited, understanding of the relationship between EM and FRP measures. Finally, we consider future directions and in particular the potential of analytical methods involving deconvolution and the potential of measurement of brain oscillatory activity.

How readers process syntactic input depends on their goals

During reading, the recognition of words is influenced by the syntactic compatibility of surrounding words: a sentence-superiority effect. However, when the goal is to make syntactic categorization decisions about single target words, these decisions are influenced by the syntactic congruency rather than compatibility of surrounding words. Although both these premises imply that readers can extract syntactic information from multiple words in parallel, they also suggest that how the brain organizes syntactic input-and consequently how surrounding stimuli affect word recognition-depends on the reader's top-down goals. The present study provides a direct test of this conception. Participants were offered nouns and verbs amidst a grammatical context ('this horse fell') and ungrammatical context ('fell horse this'). Using a conditional task setup, we manipulated the amount of emphasis put on respectively sentences and single words. In two blocks readers were instructed to make sentence grammaticality judgments only if the middle word was respectively noun or verb; in two other blocks readers were instructed to syntactically categorize the middle word only if the sentence was respectively correct or incorrect. We established an interaction effect whereby the impact of grammatical correctness on syntactic categorization decisions was greater than the effect of grammatical correctness per se. This first sentence-superiority effect in the categorization of single words, combined with the absence of this effect in prior flanker studies, leads us to surmise that word-to-word syntactic constraints only operate if the reader is engaged in sentence processing.

Dissociating lexical and sublexical contributions to transposed-word effects

When two sequences of words are presented successively for 400 ms each, it is harder to decide that the two sequences differ when the difference is generated by transposing two words compared with a condition where the same two words are replaced by different words. Interestingly, this transposed-word effect is obtained even when the first sequence is ungrammatical. One account of the effect seen with ungrammatical sequences is that participants detect mismatching letters rather than words. Under this account, the migration of letter identities across adjacent words would make it harder to judge the transposed-word condition as being different. The present experiment put this account to test by comparing transposition effects to sequences of words vs. pseudowords. We hypothesized that if same-different judgments are made on the basis of sublexical orthographic information only, then we should observe similar effects for words and pseudowords. Although transposition effects were found with pseudoword stimuli, the effects were significantly reduced compared to word sequences. This suggests that the noisy bottom-up allocation of word identities to locations along a line of text is one key mechanism driving transposed-word effects.

New Perspectives on Serialism and Parallelism in Oculomotor Control During Reading: The Multi-Constituent Unit Hypothesis

Currently there are several computational models of eye movement control that provide a good account of oculomotor behavior during reading of English and other alphabetic languages. I will provide an overview of two dominant models: E-Z Reader and SWIFT, as well as a recently proposed model: OB1-Reader. I will evaluate a critical issue of controversy among models, namely, whether words are lexically processed serially or in parallel. I will then consider reading in Chinese, a character-based, unspaced language with ambiguous word boundaries. Finally, I will evaluate the concepts of serialism and parallelism of process central to these models, and how these models might function in relation to lexical processing that is operationalized over parafoveal multi-constituent units.

Parallel, cascaded, interactive processing of words during sentence reading

Single words are easier to identify in a briefly presented syntactically correct word sequence compared with a scrambled version of the same set of words: a sentence superiority effect. Interactive-activation models of sentence comprehension can account for this phenomenon by implementing parallel processing of word identities. The cascaded and interactive nature of such processing allows sentence-level structures to influence on-going word processing. Alternatively, prior observations of a sentence superiority effect in post-cued word-in-phrase identification might be due to the sophisticated guessing of word identities on the basis of partial information about the target word and the surrounding context. Here, for the first time, we used electrophysiological recordings to plot the time-course of the sentence superiority effect. According to an interactive-activation account of this phenomenon, the effect should be visible in the N400 component, thought to reflect the mapping of word identities onto higher-level semantic and syntactic representations. Such evidence for changes in highly automatized linguistic processing is not predicted by a sophisticated guessing account. Our results revealed a robust and widespread sentence-superiority effect on the N400 component that onsets around 270 ms post-sentence onset, thus lending support to the interactive-activation account.

Word position coding in reading is noisy

In the present article, we investigate a largely unstudied cognitive process: word position coding. The question of how readers perceive word order is not trivial: Recent research has suggested that readers associate activated word representations with plausible locations in a sentence-level representation. Rather than simply being dictated by the order in which words are recognized, word position coding may be influenced by bottom-up visual cues (e.g., word length information), as well as by top-down expectations. Here we assessed how flexible word position coding is. We let readers make grammaticality judgments about four-word sentences. The incorrect sentences were constructed by transposing two words in a correct sentence (e.g., “the man can run” became “the can man run”). The critical comparison was between two types of incorrect sentence: one with a transposition of the inner two words, and one with a transposition of the outer two words (“run man can the”). We reasoned that under limited (local) flexibility, it should be easier to classify the outer-transposed sentences as incorrect, because the words were farther away from their plausible locations in this condition. If words were recognized irrespective of location, on the other hand, there should be no difference between these two conditions. As it turned out, we observed longer response times and higher error rates for inner- than for outer-transposed sentences, indicating that local flexibility and top-down expectations can jointly lead the reader to confuse the locations of words, with a probability that increases as the distance between the plausible and actual locations of a word decreases. We conclude that word position coding is subject to a moderate amount of noise.

Parallel word processing in the flanker paradigm has a rightward bias

Reading research is exhibiting growing interest in employing variants of the flanker paradigm to address several questions about reading. The paradigm is particularly suited for investigating parallel word processing, parafoveal-on-foveal influences, and visuospatial attention in a simple but constrained setting. However, this methodological deviation from natural reading warrants careful assessment of the extent to which cognitive processes underlying reading operate similarly in these respective settings. The present study investigated whether readers’ distribution of attention in the flanker paradigm resembles that observed during sentence reading; that is, with a rightward bias. Participants made lexical decisions about foveal target words while we manipulated parafoveal flanking words. In line with prior research, we established a parafoveal-on-foveal repetition effect, and this effect was increased for rightward flankers compared with leftward flankers. In a second experiment, we found that, compared with a no-flanker condition, rightward repetition flankers facilitated target processing, while leftward flankers interfered. Additionally, the repetition effect was larger for rightward than for leftward flankers. From these findings, we infer that attention in the flanker paradigm is indeed biased toward the right, and that the flanker paradigm thus provides an effective analogy to natural reading for investigating the role of visuospatial attention. The enhanced parafoveal-on-foveal effects within the attended region further underline the key role of attention in the spatial integration of orthographic information. Lastly, we conclude that future research employing the flanker paradigm should take the asymmetrical aspect of the attentional deployment into account.

Parallel spatial channels converge at a bottleneck in anterior word-selective cortex

In most environments, the visual system is confronted with many relevant objects simultaneously. That is especially true during reading. However, behavioral data demonstrate that a serial bottleneck prevents recognition of more than one word at a time. We used fMRI to investigate how parallel spatial channels of visual processing converge into a serial bottleneck for word recognition. Participants viewed pairs of words presented simultaneously. We found that retinotopic cortex processed the two words in parallel spatial channels, one in each contralateral hemisphere. Responses were higher for attended than for ignored words but were not reduced when attention was divided. We then analyzed two word-selective regions along the occipitotemporal sulcus (OTS) of both hemispheres (subregions of the visual word form area, VWFA). Unlike retinotopic regions, each word-selective region responded to words on both sides of fixation. Nonetheless, a single region in the left hemisphere (posterior OTS) contained spatial channels for both hemifields that were independently modulated by selective attention. Thus, the left posterior VWFA supports parallel processing of multiple words. In contrast, activity in a more anterior word-selective region in the left hemisphere (mid OTS) was consistent with a single channel, showing (i) limited spatial selectivity, (ii) no effect of spatial attention on mean response amplitudes, and (iii) sensitivity to lexical properties of only one attended word. Therefore, the visual system can process two words in parallel up to a late stage in the ventral stream. The transition to a single channel is consistent with the observed bottleneck in behavior.

Contralateral delay activity tracks the storage of visually presented letters and words

Electrophysiological studies have demonstrated that the maintenance of items in visual working memory (VWM) is indexed by the contralateral delay activity (CDA), which increases in amplitude as the number of objects to remember increases, plateauing at VWM capacity. Previous work has primarily utilized simple visual items, such as colored squares or picture stimuli. Despite the frequent use of verbal stimuli in seminal investigations of visual attention and memory, it is unknown whether temporary storage of letters and words also elicit a typical load-sensitive CDA. Given their close associations with language and phonological codes, it is possible that participants store these stimuli phonologically, and not visually. Participants completed a standard visual change-detection task while their ERPs were recorded. Experiment 1 compared the CDA elicited by colored squares compared to uppercase consonants, and Experiment 2 compared the CDA elicited by words compared to colored bars. Behavioral accuracy of change detection decreased with increasing set size for colored squares, letters, and words. We found that a capacity-limited CDA was present for colored squares, letters, and word arrays, suggesting that the visual codes for letters and words were maintained in VWM, despite the potential for transfer to verbal working memory. These results suggest that, despite their verbal associations, letters and words elicit the electrophysiological marker of VWM encoding and storage.

Evidence of Serial Processing in Visual Word Recognition

To test the limits of parallel processing in vision, we investigated whether people can recognize two words at once. Participants viewed brief, masked pairs of words and were instructed in advance to judge both of the words (dual-task condition) or just one of the words (single-task condition). For judgments of semantic category, the dual-task deficit was so large that it supported all-or-none serial processing: Participants could recognize only one word and had to guess about the other. Moreover, participants were more likely to be correct about one word if they were incorrect about the other, which also supports a serial-processing model. In contrast, judgments of text color with identical stimuli were consistent with unlimited-capacity parallel processing. Thus, under these conditions, serial processing is necessary to judge the meaning of words but not their physical features. Understanding the implications of this result for natural reading will require further investigation.

Using eye movements to understand the leakage of information during Chinese reading

How is attention allocated during reading? The present eye-movement experiment used a paradigm developed by Liu and Reichle (Psychological Science, 29, 278-287, 2018) to examine object-based attention during reading: Participants were instructed to read one of two spatially overlapping sentences containing colocated target/distractor words of varying frequency. Although target-word frequency modulated fixation-duration measures on the target word, the distractor-word frequency also had a smaller, independent effect. Survival analyses indicate that the distractor-word effect occurred later than the target-word effect, suggesting that subtle orthographic cues were noticed either later or occasionally, thereby modulating decisions about when to move the eyes. The theoretical ramifications of this "leakage" of information are discussed with respect to the general question of attention allocation during reading and possible differences between the reading of Chinese versus English.

Parallel graded attention in reading: A pupillometric study

There are roughly two lines of theory to account for recent evidence that word processing is influenced by adjacent orthographic information. One line assumes that multiple words can be processed simultaneously through a parallel graded distribution of visuo-spatial attention. The other line assumes that attention is strictly directed to single words, but that letter detectors are connected to both foveal and parafoveal feature detectors, as such driving parafoveal-foveal integrative effects. Putting these two accounts to the test, we build on recent research showing that the pupil responds to the brightness of covertly attended (i.e., without looking) locations in the visual field. Experiment 1 showed that foveal target word processing was facilitated by related parafoveal flanking words when these were positioned to the left and right of the target, but not when these were positioned above and below the target. Perfectly in line with this asymmetry, in Experiment 2 we found that the pupil size was contingent with the brightness of the locations of horizontally but not vertically aligned flankers, indicating that attentional resources were allocated to those words involved in the parafoveal-on-foveal effect. We conclude that orthographic parafoveal-on-foveal effects are driven by parallel graded attention.

Eye-Movement Evidence for Object-Based Attention in Chinese Reading

Is attention allocated to only one word or to multiple words at any given time during reading? The experiments reported here addressed this question using a novel paradigm inspired by classic findings on object-based attention. In Experiment 1, participants ( N = 18) made lexical decisions about one of two spatially colocated Chinese words or nonwords. Our main finding was that only the attended word's frequency influenced response times and accuracy. In Experiment 2, participants ( N = 30) read target words embedded in two spatially colocated Chinese sentences. Our key finding here was that only target-word frequencies influenced looking times and fixation positions. These results support the hypothesis that words are attended in a strictly serial (and perhaps object-based) manner during reading. The theoretical implications of this conclusion are discussed in relation to models of eye-movement control during reading and the conceptualization of words as visual objects.

Writing in the air: A visualization tool for written languages

The present study investigated interactions between cognitive processes and finger actions called “kusho,” meaning “air-writing” in Japanese. Kanji-culture individuals often employ kusho behavior in which they move their fingers as a substitute for a pen to write mostly done when they are trying to recall the shape of a Kanji character or the spelling of an English word. To further examine the visualization role of kusho behavior on cognitive processing, we conducted a Kanji construction task in which a stimulus (i.e., sub-parts to be constructed) was simultaneously presented. In addition, we conducted a Kanji vocabulary test to reveal the relation between the kusho benefit and vocabulary size. The experiment provided two sets of novel findings. First, executing kusho behavior improved task performance (correct responses) as long as the participants watched their finger movements while solving the task. This result supports the idea that visual feedback of kusho behavior helps cognitive processing for the task. Second, task performance was positively correlated with the vocabulary score when stimuli were presented for a relatively long time, whereas the kusho benefits and vocabulary score were not correlated regardless of stimulus-presentation time. These results imply that a longer stimulus-presentation could allow participants to utilize their lexical resources for solving the task. The current findings together support the visualization role of kusho behavior, adding experimental evidence supporting the view that there are interactions between cognition and motor behavior.

Effects of adults aging on word encoding in reading Chinese: evidence from disappearing text

The effect of aging on the process of word encoding for fixated words and words presented to the right of the fixation point during the reading of sentences in Chinese was investigated with two disappearing text experiments. The results of Experiment 1 showed that only the 40-ms onset disappearance of word n disrupted young adults' reading performance. However, for old readers, the disappearance of word n caused disruptions until the onset time was 120 ms. The results of Experiment 2 showed that the disappearance of word n + 1 did not cause disruptions to young adults, but these conditions made old readers spend more time reading a sentence compared to the normal display condition. These results indicated a reliable aging effect on the process of word encoding when reading Chinese, and that the encoding process in the preview frame was more susceptible to normal aging compared to that in the fixation frame. We propose that sensory, cognitive, and specific factors related to the Chinese language are important contributors to these age-related differences.

The word frequency effect during sentence reading: A linear or nonlinear effect of log frequency?

The effect of word frequency on eye movement behaviour during reading has been reported in many experimental studies. However, the vast majority of these studies compared only two levels of word frequency (high and low). Here we assess whether the effect of log word frequency on eye movement measures is linear, in an experiment in which a critical target word in each sentence was at one of three approximately equally spaced log frequency levels. Separate analyses treated log frequency as a categorical or a continuous predictor. Both analyses showed only a linear effect of log frequency on the likelihood of skipping a word, and on first fixation duration. Ex-Gaussian analyses of first fixation duration showed similar effects on distributional parameters in comparing high- and medium-frequency words, and medium- and low-frequency words. Analyses of gaze duration and the probability of a refixation suggested a nonlinear pattern, with a larger effect at the lower end of the log frequency scale. However, the nonlinear effects were small, and Bayes Factor analyses favoured the simpler linear models for all measures. The possible roles of lexical and post-lexical factors in producing nonlinear effects of log word frequency during sentence reading are discussed.

Readers extract character frequency information from nonfixated-target word at long pretarget fixations during Chinese reading

We performed 2 eye movement studies to explore whether readers can extract character or word frequency information from nonfixated-target words in Chinese reading. In Experiments 1A and 1B, we manipulated the character frequency of the first character in a 2-character target word and the word frequency of a 2-character target word, respectively. We found that fixation durations on the pretarget words were shorter when the first character of a 2-character target word was presented with high frequency. Such effects were not observed for word frequency manipulations of a 2-character target word. In particular, further analysis revealed that such effects only occurred for long pretarget fixations. These results for character and word frequency manipulations were replicated in a within-subjects design in Experiment 2. These findings are generally consistent with the notion that characters are processed in parallel during Chinese reading. However, we did not find evidence that words are processed in parallel during Chinese reading.

Preview benefit in speaking occurs regardless of preview timing

Speakers access information from objects they will name but have not looked at yet, indexed by preview benefit--faster processing of the target when a preview object previously occupying its location was related rather than unrelated to the target. This suggests that speakers distribute attention over multiple objects, but it does not reveal the time course of the processing of a current and a to-be-named object. Is the preview benefit a consequence of attention shifting to the next-to-be-named object shortly before the eyes move to that location, or does the benefit reflect a more unconstrained deployment of attention to upcoming objects? Using the multiple-object naming paradigm with a gaze-contingent display change manipulation, we addressed this issue by manipulating the latency of the onset of the preview (SOA) and whether the preview represented the same concept as (but a different visual token of) the target or an unrelated concept. The results revealed that the preview benefit was robust, regardless of the latency of the preview onset or the latency of the saccade to the target (the lag between preview offset and fixation on the target). Together, these data suggest that preview benefit is not restricted to the time during an attention shift preceding an eye movement, and that speakers are able to take advantage of information from nonfoveal objects whenever such objects are visually available.

Using E-Z Reader to examine the consequences of fixation-location measurement error

There is an ongoing debate about whether fixation durations during reading are only influenced by the processing difficulty of the words being fixated (i.e., the serial-attention hypothesis) or whether they are also influenced by the processing difficulty of the previous and/or upcoming words (i.e., the attention-gradient hypothesis). This article reports the results of 3 simulations that examine how systematic and random errors in the measurement of fixation locations can generate 2 phenomena that support the attention-gradient hypothesis: parafoveal-on-foveal effects and large spillover effects. These simulations demonstrate how measurement error can produce these effects within the context of a computational model of eye-movement control during reading (E-Z Reader; Reichle, 2011) that instantiates strictly serial allocation of attention, thus demonstrating that these effects do not necessarily provide strong evidence against the serial-attention hypothesis.

Developmental Changes in Eye Movements and Visual Information Encoding Associated With Learning to Read

A great deal of eye-movement research has resulted in sophisticated computational models of skilled adult reading. As yet, insufficient eye-movement research has been conducted with children to allow a more thorough understanding of the developmental trajectory leading up to this end state. I argue that, in order to fully understand how children progress to skilled adult reading, it is necessary to consider changes in both cognitive processing and eye-movement behavior. By recording children’s eye movements during reading, researchers can document how printed text is encoded and incrementally delivered for subsequent cognitive processing, and understand how developmental changes in these two aspects of reading are interdependent.

Examining Eye Movements in Visual Search through Clusters of Objects in a Circular Array

Participants were asked to search for a complete O in an array consisting of eight clusters of four Landolt Cs (i.e., Os with a gap) arranged in a ring. The size of the gap in the Cs varied from cluster to cluster but was held constant within a cluster. The manual response time data were consistent with a serial self-terminating search. More importantly, eye movement data supported a serial processing model as (a) clusters were fixated serially (either clockwise or counterclockwise) on most trials and (b) fixation times on a cluster reflected processing time on that cluster and were unaffected by the gap size of either the prior or succeeding cluster. Furthermore, the pattern of fixation times on a cluster was similar to the pattern of response times in a secondary task where a single cluster was presented at fixation. These data extend the findings of Williams and Pollatsek (2007) in which search was through a linear sequence of clusters, and indicate that a serial search pattern through clusters of these kinds of objects is not confined to reading-like linear arrays.

Serial and parallel processes in eye movement control: current controversies and future directions

In this editorial for the special issue on serial and parallel processing in reading we explore the background to the current debate concerning whether the word recognition processes in reading are strictly serial-sequential or take place in an overlapping parallel fashion. We consider the history of the controversy and some of the underlying assumptions, together with an analysis of the types of evidence and arguments that have been adduced to both sides of the debate, concluding that both accounts necessarily presuppose some weakening of, or elasticity in, the eye-mind assumption. We then consider future directions, both for reading research and for scene viewing, and wrap up the editorial with a brief overview of the following articles and their conclusions.