The influence of semantic context on initial eye landing sites in words

Word Frequency and Predictability Dissociate in Naturalistic Reading

Many studies of human language processing have shown that readers slow down at less frequent or less predictable words, but there is debate about whether frequency and predictability effects reflect separable cognitive phenomena: are cognitive operations that retrieve words from the mental lexicon based on sensory cues distinct from those that predict upcoming words based on context? Previous evidence for a frequency-predictability dissociation is mostly based on small samples (both for estimating predictability and frequency and for testing their effects on human behavior), artificial materials (e.g., isolated constructed sentences), and implausible modeling assumptions (discrete-time dynamics, linearity, additivity, constant variance, and invariance over time), which raises the question: do frequency and predictability dissociate in ordinary language comprehension, such as story reading? This study leverages recent progress in open data and computational modeling to address this question at scale. A large collection of naturalistic reading data (six datasets, >2.2 M datapoints) is analyzed using nonlinear continuous-time regression, and frequency and predictability are estimated using statistical language models trained on more data than is currently typical in psycholinguistics. Despite the use of naturalistic data, strong predictability estimates, and flexible regression models, results converge with earlier experimental studies in supporting dissociable and additive frequency and predictability effects.

Joint effects of individual reading skills and word properties on Chinese children's eye movements during sentence reading

Word recognition during the reading of continuous text has received much attention. While a large body of research has investigated how linguistic properties of words affect eye movements during reading, it remains to be established how individual differences in reading skills affect momentary cognitive processes during sentence reading among typically developing Chinese readers. The present study set out to test the joint influences of word properties and individual reading skills on eye movements during reading among Chinese children. We recorded eye movements of 30 grade 3 (G3) children and 27 grade 5 (G5) children when they read sentences silently for comprehension. Predictors of linear mixed models included word frequency, visual complexity, and launch site distance, in addition to the participants' offline psychometric performances in rapid naming, morphological awareness, word segmenting, and character recognition. The results showed that word properties affected word recognition during sentence reading in both G3 and G5 children. Moreover, word segmenting predicted the G3 children's fixation durations and the G5 children's fixation location, whereas rapid naming predicted the G5 children's fixation duration. Implications are discussed based on the current findings, in light of how different literacy skills contribute to reading development.

Eye movements during reading in beginning and skilled readers: Impact of reading level or physiological maturation?

We begin by presenting and examining relevant data in the literature on eye movements in reading, from childhood to adulthood. In particular, we discuss the differences found in eye movements during reading between children in different age groups and with different reading levels and skilled adult readers in terms of word recognition and sentence processing. We then critically discuss two hypotheses that account for the differences between children and adults' eye movement during reading: one being reading age itself - the changes in eye movement patterns in reading are regulated by the level of reading proficiency and its automatization - and the other being the role of maturation of oculomotor control and, consequently, its possible changes in eye movement patterns during reading. Finally, we list gaps in the research field and suggest that future research will benefit from investigating eye movements during reading in ex-illiterate adults who are in the process of learning to read in order to isolate both reading and maturational factors.

Eye Movement Control in Tibetan Reading: The Roles of Word Length and Frequency

We investigated the effects of word length and frequency on eye movement control during Tibetan reading through two experiments. A preliminary experiment examined the predictive effect of word length and frequency on fixation duration and landing position using multiple linear regression analysis. In the formal experiment, we manipulated the length and frequency of target words simultaneously to investigate the effects of word length and frequency on fixation duration and landing position in Tibetan reading. In this study, we found that: (1) there were significant word-length and word-frequency effects affecting all lexical processing in Tibetan reading; (2) there are preferred viewing locations in Tibetan reading; specifically, for short words, it is the end, whereas for long words, it spans from the center to the beginning of the word; (3) word frequency does not affect preferred viewing location in Tibetan reading; (4) the preferred viewing position and the interaction of word length and viewing position found in this study supported the “strategy-tactics” approach.

Probability, Dependency, and Frequency Are Not All Equally Involved in Statistical Learning

The ability to learn sequences depends on different factors governing sequence structure, such as transitional probability (TP, probability of a stimulus given a previous stimulus), adjacent or nonadjacent dependency, and frequency. Current evidence indicates that adjacent and nonadjacent pairs are not equally learnable; the same applies to second-order and first-order TPs and to the frequency of the sequences. However, the relative importance of these factors and interactive effects on learning remain poorly understood. The first experiment tested the effects of TPs and dependency separately on the learning of nonlinguistic visual sequences, and the second experiment used the factors of the first experiment and added a frequency factor to test their interactive effects with verbal sequences of stimuli (pseudo-words). The results of both experiments showed higher performance during online learning for first-order TPs in adjacent pairs. Moreover, Experiment 2 indicated poorer performance during offline recall for nonadjacent dependencies and low-frequency sequences. We discuss the results that different factors are not used equally in prediction and memorization.

Dynamic branching in a neural network model for probabilistic prediction of sequences

An important function of the brain is to predict which stimulus is likely to occur based on the perceived cues. The present research studied the branching behavior of a computational network model of populations of excitatory and inhibitory neurons, both analytically and through simulations. Results show how synaptic efficacy, retroactive inhibition and short-term synaptic depression determine the dynamics of selection between different branches predicting sequences of stimuli of different probabilities. Further results show that changes in the probability of the different predictions depend on variations of neuronal gain. Such variations allow the network to optimize the probability of its predictions to changing probabilities of the sequences without changing synaptic efficacy.

The Beijing Sentence Corpus: A Chinese sentence corpus with eye movement data and predictability norms

This report introduces the Beijing Sentence Corpus (BSC). This is a Chinese sentence corpus of eye-tracking data with relatively clear word boundaries. In addition, we report predictability norms for each word in the corpus. Eye movement corpora are available in alphabetic scripts such as English, German, and French. However, there is no publicly available corpus for Chinese. Thus, to study predictive processes during reading in Chinese, it is necessary to establish such a corpus. Also, given the clear word boundaries in the sentences, BSC is especially useful to provide evidence relevant to the theoretical debate of saccade target selection in Chinese. With the large-scale predictability norms, we conducted new analyses based on 60 BSC readers, testing the influences of launch word and target word properties while controlling for visual and oculomotor constraints, as well as sentence and subject-level individual differences. We discuss implications for guidance of eye movements in Chinese reading.

Modulation of oculomotor control during reading of mirrored and inverted texts

The interplay between cognitive and oculomotor processes during reading can be explored when the spatial layout of text deviates from the typical display. In this study, we investigate various eye-movement measures during reading of text with experimentally manipulated layout (word-wise and letter-wise mirrored-reversed text as well as inverted and scrambled text). While typical findings (e.g., longer mean fixation times, shorter mean saccades lengths) in reading manipulated texts compared to normal texts were reported in earlier work, little is known about changes of oculomotor targeting observed in within-word landing positions under the above text layouts. Here we carry out precise analyses of landing positions and find substantial changes in the so-called launch-site effect in addition to the expected overall slow-down of reading performance. Specifically, during reading of our manipulated text conditions with reversed letter order (against overall reading direction), we find a reduced launch-site effect, while in all other manipulated text conditions, we observe an increased launch-site effect. Our results clearly indicate that the oculomotor system is highly adaptive when confronted with unusual reading conditions.

Linguistic processes do not beat visuo-motor constraints, but they modulate where the eyes move regardless of word boundaries: Evidence against top-down word-based eye-movement control during reading

Where readers move their eyes, while proceeding forward along lines of text, has long been assumed to be determined in a top-down word-based manner. According to this classical view, readers of alphabetic languages would invariably program their saccades towards the center of peripheral target words, as selected based on the (expected) needs of ongoing (word-identification) processing, and the variability in within-word landing positions would exclusively result from systematic and random errors. Here we put this predominant hypothesis to a strong test by estimating the respective influences of language-related variables (word frequency and word predictability) and lower-level visuo-motor factors (word length and saccadic launch-site distance to the beginning of words) on both word-skipping likelihood and within-word landing positions. Our eye-movement data were collected while forty participants read 316 pairs of sentences, that differed only by one word, the prime; this was either semantically related or unrelated to a following test word of variable frequency and length. We found that low-level visuo-motor variables largely predominated in determining which word would be fixated next, and where in a word the eye would land. In comparison, language-related variables only had tiny influences. Yet, linguistic variables affected both the likelihood of word skipping and within-word initial landing positions, all depending on the words’ length and how far on average the eye landed from the word boundaries, but pending the word could benefit from peripheral preview. These findings provide a strong case against the predominant word-based account of eye-movement guidance during reading, by showing that saccades are primarily driven by low-level visuo-motor processes, regardless of word boundaries, while being overall subject to subtle, one-off, language-based modulations. Our results also suggest that overall distributions of saccades’ landing positions, instead of truncated within-word landing-site distributions, should be used for a better understanding of eye-movement guidance during reading.

Co-registration of eye movements and neuroimaging for studying contextual predictions in natural reading

Sixteen years ago, Sereno and Rayner (2003. Measuring word recognition in reading: eye movements and event-related potentials. Trends in Cognitive Sciences, 7(11), 489-493) illustrated how "by means of review and comparison" eye movement (EM) and event-related potential (ERP) studies may advance our understanding of visual word recognition. Attempts to simultaneously record EMs and ERPs soon followed. Recently, this co-registration approach has also been transferred to fMRI and oscillatory EEG. With experimental settings close to natural reading, co-registration enables us to directly integrate insights from EM and neuroimaging studies. This should extend current experimental paradigms by moving the field towards studying sentence-level processing including effects of context and parafoveal preview. This article will introduce the basic principles and applications of co-registration and selectively review how this approach may shed light on one of the most controversially discussed issues in reading research, contextual predictions in online language processing.

Linguistic and nonlinguistic influences on the eyes' landing positions during reading

Two eye tracking experiments show that, for near launch sites, the eyes land nearer to the beginning of words with orthographically irregular than with regular initial letter sequences. In addition, the characteristics of words, at least at the level of orthography, influence the direction and length of within-word saccades. Importantly, these effects hold both for lower case and for visually less distinctive upper case text. Furthermore, contrary to previous evidence (Tinker & Paterson, 1939), there is little effect of type case on reading times. Additional analyses of oculomotor behaviour suggest that there is an inverted optimal viewing position for single fixation durations on words. Both the supplementary analyses and the effects of orthography on fixation positions are relevant to current models of eye movements in reading.

Latching dynamics in neural networks with synaptic depression

Prediction is the ability of the brain to quickly activate a target concept in response to a related stimulus (prime). Experiments point to the existence of an overlap between the populations of the neurons coding for different stimuli, and other experiments show that prime-target relations arise in the process of long term memory formation. The classical modelling paradigm is that long term memories correspond to stable steady states of a Hopfield network with Hebbian connectivity. Experiments show that short term synaptic depression plays an important role in the processing of memories. This leads naturally to a computational model of priming, called latching dynamics; a stable state (prime) can become unstable and the system may converge to another transiently stable steady state (target). Hopfield network models of latching dynamics have been studied by means of numerical simulation, however the conditions for the existence of this dynamics have not been elucidated. In this work we use a combination of analytic and numerical approaches to confirm that latching dynamics can exist in the context of a symmetric Hebbian learning rule, however lacks robustness and imposes a number of biologically unrealistic restrictions on the model. In particular our work shows that the symmetry of the Hebbian rule is not an obstruction to the existence of latching dynamics, however fine tuning of the parameters of the model is needed.

Word predictability affects saccade length in Chinese reading: An evaluation of the dynamic-adjustment model

How does a word's within-sentence predictability influence saccade length during reading? An eye-movement experiment manipulating the predictability of target words indicates that, relative to low-predictability target words, high-predictability targets elicit longer saccades to themselves. Simulations using computational models that respectively instantiate the targeting of saccades to default locations (Yan, Kliegl, Richter, Nuthmann, & Shu in Journal of Experimental Psychology, 63, 705-725, 2010) versus the dynamic adjustment of saccade length (Liu, Reichle, & Li in Journal of Experimental Psychology Learning Memory and Cognition, 41, 1229-1236, 2015, Journal of Experimental Psychology: Human Perception and Performance, 42, 1008-1025, 2016) indicate that the latter model provides a more accurate and parsimonious account of saccade-targeting behavior in Chinese reading. The implications of these conclusions are discussed with respect to current models of eye-movement control during reading and the necessity to explain eye movements in languages as different as Chinese versus English.

Linked linear mixed models: A joint analysis of fixation locations and fixation durations in natural reading

The complexity of eye-movement control during reading allows measurement of many dependent variables, the most prominent ones being fixation durations and their locations in words. In current practice, either variable may serve as dependent variable or covariate for the other in linear mixed models (LMMs) featuring also psycholinguistic covariates of word recognition and sentence comprehension. Rather than analyzing fixation location and duration with separate LMMs, we propose linking the two according to their sequential dependency. Specifically, we include predicted fixation location (estimated in the first LMM from psycholinguistic covariates) and its associated residual fixation location as covariates in the second, fixation-duration LMM. This linked LMM affords a distinction between direct and indirect effects (mediated through fixation location) of psycholinguistic covariates on fixation durations. Results confirm the robustness of distributed processing in the perceptual span. They also offer a resolution of the paradox of the inverted optimal viewing position (IOVP) effect (i.e., longer fixation durations in the center than at the beginning and end of words) although the opposite (i.e., an OVP effect) is predicted from default assumptions of psycholinguistic processing efficiency: The IOVP effect in fixation durations is due to the residual fixation-location covariate, presumably driven primarily by saccadic error, and the OVP effect (at least the left part of it) is uncovered with the predicted fixation-location covariate, capturing the indirect effects of psycholinguistic covariates. We expect that linked LMMs will be useful for the analysis of other dynamically related multiple outcomes, a conundrum of most psychonomic research.

The Word Frequency Effect on Saccade Targeting during Chinese Reading: Evidence from a Survival Analysis of Saccade Length

Our study employs distributional analysis (i.e., survival analysis) to examine how the frequency of target words influences saccade lengths into and out of these target words in Chinese reading. The results of survival analysis indicate the survival curves in the high- and low-frequency conditions diverge for a short saccade length, with more than 80% of the lengths of incoming and outgoing saccades being larger than the divergence points. These results as well as simulations using the novel Dynamic-adjustment Model of saccadic targeting (Liu et al., 2016) are consistent with previous mean-based results and provide more precise information to support this novel model. The implications for saccade target selection during the reading of Chinese are discussed.

Patients with mild Alzheimer's disease produced shorter outgoing saccades when reading sentences

In the present work we analyzed forward saccades of thirty five elderly subjects (Controls) and of thirty five mild Alzheimer's disease (AD) during reading regular and high-predictable sentences. While they read, their eye movements were recorded. The pattern of forward saccade amplitudes as a function of word predictability was clearly longer in Controls. Our results suggest that Controls might use stored information of words for enhancing their reading performance. Further, cloze predictability increased outgoing saccades amplitudes, as this increase stronger in high-predictable sentences. Quite the contrary, patients with mild AD evidenced reduced forward saccades even at early stages of the disease. This reduction might reveal impairments in brain areas such as those corresponding to working memory, memory retrieval, and semantic memory functions that are already present at early stages of AD. Our findings might be relevant for expanding the options for the early detection and monitoring of in the early stages of AD. Furthermore, eye movements during reading could provide a new tool for measuring a drug's impact on patient's behavior.

The Effects of Reading Comprehension and Launch Site on Frequency–Predictability Interactions during Paragraph Reading

We used eye movement measures of paragraph reading to examine whether word frequency and predictability interact during the earliest stages of lexical processing, with a specific focus on whether these effects are modulated by individual differences in reading comprehension or launch site (i.e., saccade length between the prior and currently fixated word—a proxy for the amount of parafoveal word processing). The joint impact of frequency and predictability on reading will elucidate whether these variables additively or multiplicatively affect the earliest stages of lexical access, which, in turn, has implications for computational models of eye movements during reading. Linear mixed effects models revealed additive effects during both early- and late-stage reading, where predictability effects were comparable for low- and high-frequency words. Moreover, less cautious readers (e.g., readers who engaged in skimming, scanning, mindless reading) demonstrated smaller frequency effects than more cautious readers. Taken together, our findings suggest that during extended reading, frequency and predictability exert additive influences on lexical and postlexical processing, and that individual differences in reading comprehension modulate sensitivity to the effects of word frequency.

Frequency and predictability effects in the Dundee Corpus: An eye movement analysis

Analyses carried out on a large corpus of eye movement data were used to comment on four contentious theoretical issues. The results provide no evidence that word frequency and word predictability have early interactive effects on inspection time. Contrary to some earlier studies, in these data there is little evidence that properties of a prior word generally spill over and influence current processing. In contrast, there is evidence that both the frequency and the predictability of a word in parafoveal vision influence foveal processing. In the case of predictability, the direction of the effect suggests that more predictable parafoveal words produce longer foveal fixations. Finally, there is evidence that information about word class modulates processing over a span greater than a single word. The results support the notion of distributed parallel processing.

Eye movements in reading: some theoretical context

The study of eye movements has proven to be one of the most successful approaches in research on reading. In this overview, it is argued that a major reason for this success is that eye movement measurement is not just a methodology--the control of eye movements is actually part and parcel of the dynamics of information processing within the task of reading itself. Some major developments over the last decade are discussed with a focus on the issue of spatially distributed word processing and its relation to the development of reading models. The survey ends with a description of two newly emerging trends in the field: the study of continuous reading in non-Roman writing systems and the broadening of the scope of research to encompass individual differences and developmental issues.

Word-Initial Letters Influence Fixation Durations during Fluent Reading

The present study examined how word-initial letters influence lexical access during reading. Eye movements were monitored as participants read sentences containing target words. Three factors were independently manipulated. First, target words had either high or low constraining word-initial letter sequences (e.g., dwarf or clown, respectively). Second, targets were either high or low in frequency of occurrence (e.g., train or stain, respectively). Third, targets were embedded in either biasing or neutral contexts (i.e., targets were high or low in their predictability). This 2 (constraint) × 2 (frequency) × 2 (context) design allowed us to examine the conditions under which a word's initial letter sequence could facilitate processing. Analyses of fixation duration data revealed significant main effects of constraint, frequency, and context. Moreover, in measures taken to reflect "early" lexical processing (i.e., first and single fixation duration), there was a significant interaction between constraint and context. The overall pattern of findings suggests lexical access is facilitated by highly constraining word-initial letters. Results are discussed in comparison to recent studies of lexical features involved in word recognition during reading.

Determinants of multiple semantic priming: a meta-analysis and spike frequency adaptive model of a cortical network

Recall and language comprehension while processing sequences of words involves multiple semantic priming between several related and/or unrelated words. Accounting for multiple and interacting priming effects in terms of underlying neuronal structure and dynamics is a challenge for current models of semantic priming. Further elaboration of current models requires a quantifiable and reliable account of the simplest case of multiple priming resulting from two primes on a target. The meta-analytic approach offers a better understanding of the experimental data from studies on multiple priming regarding the additivity pattern of priming. The meta-analysis points to the effects of prime-target stimuli onset asynchronies on the pattern of underadditivity, overadditivity, or strict additivity of converging activation from multiple primes. The modeling approach is then constrained by results of the meta-analysis. We propose a model of a cortical network embedding spike frequency adaptation, which allows frequency and time-dependent modulation of neural activity. Model results give a comprehensive understanding of the meta-analysis results in terms of dynamics of neuron populations. They also give predictions regarding how stimuli intensities, association strength, and spike frequency adaptation influence multiple priming effects.

Semantic priming in a cortical network model

Contextual recall in humans relies on the semantic relationships between items stored in memory. These relationships can be probed by priming experiments. Such experiments have revealed a rich phenomenology on how reaction times depend on various factors such as strength and nature of associations, time intervals between stimulus presentations, and so forth. Experimental protocols on humans present striking similarities with pair association task experiments in monkeys. Electrophysiological recordings of cortical neurons in such tasks have found two types of task-related activity, "retrospective" (related to a previously shown stimulus), and "prospective" (related to a stimulus that the monkey expects to appear, due to learned association between both stimuli). Mathematical models of cortical networks allow theorists to understand the link between the physiology of single neurons and synapses, and network behavior giving rise to retrospective and/or prospective activity. Here, we show that this type of network model can account for a large variety of priming effects. Furthermore, the model allows us to interpret semantic priming differences between the two hemispheres as depending on a single association strength parameter.

Lexical Predictability Exerts Robust Effects on Fixation Duration, but not on Initial Landing Position During Reading

An eye movement experiment was conducted to examine effects of local lexical predictability on fixation durations and fixation locations during sentence reading. In the high-predictability condition, a verb strongly constrained the lexical identity of the following word, while in the low-predictability condition the target word could not be predicted on the basis of the verb. The results showed that first fixation and gaze duration on the target noun were reliably shorter in the high-predictability than in the low-predictability condition. However, initial fixation location was not affected by lexical predictability. As regards eye guidance in reading, the present study indicates that local lexical predictability influences when decisions but not where the initial fixation lands in a word.

Rightward bisection errors for letter lines: The role of semantic information

When bisecting words in their middle, people reveal leftward bisection errors. This tendency might emerge from an attentional bias towards the beginning of the word. However, when longer meaningless letter strings are presented, people reveal a rightward bisection bias. To test the role of semantic information on leftward or rightward bisection biases, we tested letter line bisection performance in healthy right-handed students in four independent experiments. A third of the letter lines contained an embedded four-letter word to the left of true centre, another third contained an embedded four-letter word to the right of true centre, while the remaining lines contained no words. Half of these words were emotional words, the other half were neutral words. Results across experiments revealed a stronger rightward bisection bias: (i) for letter lines containing emotional as compared to neutral words, (ii) for letter lines containing words in the left as compared to right half of the lines, and (iii) for those experiments in which the spatial position of letter lines remained within a narrow body-centred space. Findings from this study suggest that letter line bisection performance might be only minimally determined by visuo-spatial attention. Rather, letter line perception might activate the left hemisphere more than the right hemisphere, shifting the subjective midpoint to the right of true centre. Leftward bisection biases for words only, as had been described in the literature, may thus have resulted from automated reading strategies rather than from attentional biases towards the left hemispace.

Tracking the mind during reading: the influence of past, present, and future words on fixation durations

Reading requires the orchestration of visual, attentional, language-related, and oculomotor processing constraints. This study replicates previous effects of frequency, predictability, and length of fixated words on fixation durations in natural reading and demonstrates new effects of these variables related to 144 sentences. Such evidence for distributed processing of words across fixation durations challenges psycholinguistic immediacy-of-processing and eye-mind assumptions. Most of the time the mind processes several words in parallel at different perceptual and cognitive levels. Eye movements can help to unravel these processes.

Effects of contextual predictability and transitional probability on eye movements during reading

In 2 eye-movement experiments, the authors tested whether transitional probability (the statistical likelihood that a word precedes or follows another word) affects reading times and whether this occurs independently from contextual predictability effects. Experiment 1 showed early effects of predictability, replicating S. A. McDonald and R. C. Shillcock's (2003a) finding that words with a high transitional probability (defeat following accept) are read faster than words with a low transitional probability (losses following accept). However, further analyses suggested that the transitional probability effect was likely due to differences in predictability rather than transitional probability. Experiment 2, using a better controlled set of items, again showed an effect of predictability, but no effect of transitional probability. The authors conclude that effects of transitional probability are part of regular predictability effects. Their data also show that predictability effects are detectable very early in the eye-movement record and between contexts that are weakly constraining.

The effects of frequency and predictability on eye fixations in reading: implications for the E-Z Reader model

Readers read sentences containing target words varying in frequency and predictability. The observed pattern of data for fixation durations only mildly departed from additivity, with predictability effects that were slightly larger for low-frequency than for high-frequency words. The pattern of data for skipping was different as predictability affected only the probability of skipping for high-frequency target words. Simulations of these data using the E-Z Reader model indicated that a single-process model was unlikely to provide a good fit for both measures. A version of the model that assumes that (a) word-encoding time is additively affected by frequency and predictability and (b) difficulty with postlexical processing of the target word causes a double take accounted for the data while indicating that the relationship between the duration of hypothesized word-encoding stages and observed fixation durations is not likely to be transparent.

"Bottom-up" and "top-down" effects on reading saccades: a case study

OBJECTIVE

To investigate the role right foveal/parafoveal sparing plays in reading single words, word arrays, and eye movement patterns in a single case with an incongruous hemianopia.

METHODS

The patient, a 48-year-old right handed male with a macular sparing hemianopia in his left eye and a macular splitting hemianopia in his right eye, performed various reading tasks. Single word reading speeds were monitored using a "voice-trigger" system. Eye movements were recorded while reading three passages of text, and PET data were gathered while the subject performed a variety of reading tasks in the camera.

RESULTS

The patient was faster at reading single words and text with his left eye compared with his right. A small word length effect was present in his right eye but not his left. His eye movement patterns were more orderly when reading text with his left eye, making fewer saccades. The PET data provided evidence of "top-down" processes involved in reading. Binocular single word reading produced activity in the representation of foveal V1 bilaterally; however, text reading with the left eye only was associated with activation in left but not right parafoveal V1, despite there being visual stimuli in both visual fields.

CONCLUSIONS

The presence of a word length effect (typically associated with pure alexia) can be caused by a macular splitting hemianopia. Right parafoveal vision is not critically involved in single word identification, but is when planning left to right reading saccades. The influence of top-down attentional processes during text reading can be visualised in parafoveal V1 using PET.

Low-level predictive inference in reading: the influence of transitional probabilities on eye movements

We report the results of an investigation into the ability of transitional probability (word-to-word contingency statistics) to account for reading behaviour. Using a corpus of eye movements recorded during the reading of newspaper text, we demonstrate both the forward [P(n/n-1)] and backward [P(n/n+1)] transitional probability measures to be predictive of first fixation and gaze durations: the higher the transitional probability, the shorter the fixation time. Initial fixation position was also affected by the forward measure; we observed a small rightward shift for words that were highly predictable from the preceding word. Although transitional probability is sensitive to word class, with function words being generally more predictable from their context than content words, the measures accounted equally well for the data for both classes.

Eye movements and processing stages in reading: relative contribution of visual, lexical, and contextual factors

The independent and the combined influence of word length, word frequency, and contextual predictability on eye movements in reading was examined across processing stages under two priming-context conditions. Length, frequency, and predictability were used as predictors in multiple regression analyses, with parafoveal, early, late, and spillover eye movement measures as the dependent variables. There were specific effects of: (a) length, both on where to look (how likely a word was fixated and in which location) and how long to fixate, across all processing stages; (b) frequency, on how long to fixate a word, but not on where to look, at an early processing stage; and (c) predictability, both on how likely a word was fixated and for how long, in late processing stages. The source of influence for predictability was related to global rather than to local contextual priming. The contribution of word length was independent of contextual source. These results are relevant to determine both the time course of the influence of visual, lexical, and contextual factors on eye movements in reading, and which main component of eye movements, that is, location or duration, is affected.

Eye movements during reading: some current controversies

For many researchers, eye-movement measures have become instrumental in revealing the moment-to-moment activity of the mind during reading. In general, there has been a great deal of consistency across studies within the eye-movement literature, and researchers have discovered and examined many variables involved in the reading process that affect the nature of readers' eye movements. Despite remarkable progress, however, there are still a number of issues to be resolved. In this article, we discuss three controversial issues: (1) the extent to which eye-movement behavior is affected by low-level oculomotor factors versus higher-level cognitive processes; (2) how much information is extracted from the right of fixation; and (3) whether readers process information from more than one word at a time.

Eye movement control in reading: word predictability has little influence on initial landing positions in words

We examined the initial landing position of the eyes in target words that were either predictable or unpredictable from the preceding sentence context. Although readers skipped over predictable words more than unpredictable words and spent less time on predictable words when they did fixate on them, there was no difference in the launch site of the saccade to the target word. Moreover, there was only a very small difference in the initial landing position on the target word as a function of predictability when the target words were fixated which is most parsimoniously explained by positing that a few programmed skips of the target word fell short of their intended target. These results suggest that low-level processing is primarily responsible for landing position effects in reading.