The 'center of gravity' of words: evidence for an effect of the word-initial letters

Space-Time Congruency Effects Using Eye Movements During Processing of Past- and Future-Related Words

In Western cultures where people read and write from left to right, time is represented along a spatial continuum that goes from left to right (past to future), known as the mental timeline (MTL). In language, this MTL was supported by space-time congruency effects: People are faster to make lexical decisions to words conveying past or future information when left/right manual responses are compatible with the MTL. Alternatively, in cultures where people read from right to left, space-time congruency effects go in the opposite direction. Such cross-cultural differences suggest that repeated writing and reading dynamic movements are critically involved in the spatial representation of time. In most experiments on the space-time congruency effect, participants use their hand for responding, an effector that is associated to the directionality of writing. To investigate the role of the directionality of reading in the space-time congruency effect, we asked participants to make lateralized eye movements (left or right saccades) to indicate whether stimuli were real words or not (lexical decision). Eye movement responses were slower and higher in amplitude for responses incompatible with the direction of the MTL. These results reinforce the claim that repeated directional reading and writing movements promote the embodiment of time-related words.

Do readers use character information when programming return-sweep saccades?

Reading saccades that occur within a single line of text are guided by the size of letters. However, readers occasionally need to make longer saccades (known as return-sweeps) that take their eyes from the end of one line of text to the beginning of the next. In this study, we tested whether return-sweep saccades are also guided by font size information and whether this guidance depends on visual acuity of the return-sweep target area. To do this, we manipulated the font size of letters (0.29 vs 0.39° per character) and the length of the first line of text (16 vs 26°). The larger font resulted in return-sweeps that landed further to the right of the line start and in a reduction of under-sweeps compared to the smaller font. This suggests that font size information is used when programming return-sweeps. Return-sweeps in the longer line condition landed further to the right of the line start and the proportion of under-sweeps increased compared to the short line condition. This likely reflects an increase in saccadic undershoot error with the increase in intended saccade size. Critically, there was no interaction between font size and line length. This suggests that when programming return-sweeps, the use of font size information does not depend on visual acuity at the saccade target. Instead, it appears that readers rely on global typographic properties of the text in order to maintain an optimal number of characters to the left of their first fixation on a new line.

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.

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.

Morphological structure influences the initial landing position in words during reading Finnish

The preferred viewing location in words [Rayner, K. (1979). Eye guidance in reading: Fixation locations within words. Perception, 8, 21-30] during reading is near the word centre. Parafoveal word length information is utilized to guide the eyes toward it. A recent study by Yan and colleagues [Yan, M., Zhou, W., Shu, H., Yusupu, R., Miao, D., Krügel, A., & Kliegl, R. (2014). Eye movements guided by morphological structure: Evidence from the Uighur language. Cognition, 132, 181-215] demonstrated that the word's morphological structure may also be used in saccadic targeting. The study was conducted in a morphologically rich language, Uighur. The present study aimed at replicating their main findings in another morphologically rich language, Finnish. Similarly to Yan et al., it was found that the initial fixation landed closer to the word beginning for morphologically complex than for monomorphemic words. Word frequency, saccade launch site, and word length were also found to influence the initial landing position. It is concluded that in addition to low-level factors (word length and saccade launch site), also higher level factors related to the word's morphological structure and frequency may be utilized in saccade programming during reading.

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

Previous research has demonstrated that readers use word length and word boundary information in targeting saccades into upcoming words while reading. Previous studies have also revealed that the initial landing positions for fixations on words are affected by parafoveal processing. In the present study, we examined the effects of word length and orthographic legality on targeting saccades into parafoveal words. Long (8-9 letters) and short (4-5 letters) target words, which were matched on lexical frequency and initial letter trigram, were paired and embedded into identical sentence frames. The gaze-contingent boundary paradigm (Rayner, 1975) was used to manipulate the parafoveal information available to the reader before direct fixation on the target word. The parafoveal preview was either identical to the target word or was a visually similar nonword. The nonword previews contained orthographically legal or orthographically illegal initial letters. The results showed that orthographic preprocessing of the word to the right of fixation affected eye movement targeting, regardless of word length. Additionally, the lexical status of an upcoming saccade target in the parafovea generally did not influence preprocessing.

Assessing the Role of Hemispheric Specialisation, Serial-Position Processing, and Retinal Eccentricity in Lateralised Word RecognitioN

The advantage for words in the right visual hemifield (RVF) has been assigned parallel orthographic processing by the left hemisphere and sequential by the right. However, an examination of previous studies of serial position performance suggests that orthographic processing in each hemifield is modulated by retinal eccentricity. To investigate this issue, we presented words at eccentricities of 1, 2, 3, and 4 degrees. Serial position performance was measured using the Reicher-Wheeler task to suppress influences of guesswork and an eye-tracker controlled fixation location. Greater eccentricities produced lower overall levels of performance in each hemifield although RVF advantages for words obtained at each eccentricity (Experiments 1 and 2). However, performance in both hemifields revealed similar U-shaped serial position performance at all eccentricities. Moreover, this performance was not influenced by lexical constraint (high, low; Experiment 2) or status (word, nonword; Experiment 3), although only words (not nonwords) produced an RVF advantage. These findings suggest that although each RVF advantage was produced by left-hemisphere function, the same pattern of orthographic analysis was used by each hemisphere at each eccentricity.

The influence of word shading and word length on eye movements during reading

An interesting issue in reading is how parafoveal information affects saccadic targeting and fixation durations. We investigated the influence of shading selected regions of text on eye movements during reading of long and short words within sentences. A target word, either four- or eight-letters long, was presented in one of four shading conditions: the whole target word shaded; the first half shaded; second half shaded; no shading. There was no evidence of a visually mediated parafoveal-on-foveal effect. Saccadic targeting was modulated by the shading on the first half of the word, such that fixations landed closer to the beginning of the word than in the other three shading conditions. Furthermore, partial word shading, resulting in visual non-uniformity of the target word, produced longer gaze durations than the other conditions. Finally, readers spent more time re-reading target words when they were partially shaded than in the other two conditions. We suggest that our effects are due to targeting of the optimal viewing location and revisits to check words that appear visually unusual. Together, the results indicate robust effects of low-level visual characteristics of the word on oculomotor decisions of where and when to move the eyes during reading.

Evaluating effects of divided hemispheric processing on word recognition in foveal and extrafoveal displays: the evidence from Arabic

Background

Previous studies have claimed that a precise split at the vertical midline of each fovea causes all words to the left and right of fixation to project to the opposite, contralateral hemisphere, and this division in hemispheric processing has considerable consequences for foveal word recognition. However, research in this area is dominated by the use of stimuli from Latinate languages, which may induce specific effects on performance. Consequently, we report two experiments using stimuli from a fundamentally different, non-Latinate language (Arabic) that offers an alternative way of revealing effects of split-foveal processing, if they exist.

Methods and Findings

Words (and pseudowords) were presented to the left or right of fixation, either close to fixation and entirely within foveal vision, or further from fixation and entirely within extrafoveal vision. Fixation location and stimulus presentations were carefully controlled using an eye-tracker linked to a fixation-contingent display. To assess word recognition, Experiment 1 used the Reicher-Wheeler task and Experiment 2 used the lexical decision task.

Results

Performance in both experiments indicated a functional division in hemispheric processing for words in extrafoveal locations (in recognition accuracy in Experiment 1 and in reaction times and error rates in Experiment 2) but no such division for words in foveal locations.

Conclusions

These findings from a non-Latinate language provide new evidence that although a functional division in hemispheric processing exists for word recognition outside the fovea, this division does not extend up to the point of fixation. Some implications for word recognition and reading are discussed.

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.

Attentional selection during preparation of eye movements

Two experiments were conducted to examine the relationship between visual attention and saccade programming. Participants had to saccade to a letter string and detect a letter change presented briefly before the saccade onset. Hit probability (i.e., correct detection of a letter change in different positions) was taken as a measure of visual attention focus. The first experiment shows that hit probability depends on the actual landing position. These findings argue for a spatial coupling between saccade programming and the orienting of attention. Also, an unfamiliar letter cluster at the beginning captures attention and prevails over the influence of the saccade in preparation. Experiment 2, in which the letter change occurred at different times during the saccade latency, shows that attention shifts and focuses on the saccade target at the expense of the other parts of the stimulus when the motor program is ready to be executed. The theoretical implications of these results are discussed.

A magnetic stimulation examination of orthographic neighborhood effects in visual word recognition

The split-fovea theory proposes that visual word recognition is mediated by the splitting of the foveal image, with letters to the left of fixation projected to the right hemisphere (RH) and letters to the right of fixation projected to the left hemisphere (LH). We applied repetitive transcranial magnetic stimulation (rTMS) over the left and right occipital cortex during a lexical decision task to investigate the extent to which word recognition processes could be accounted for according to the split-fovea theory. Unilateral rTMS significantly impaired lexical decision latencies to centrally presented words, supporting the suggestion that foveal representation of words is split between the cerebral hemispheres rather than bilateral. Behaviorally, we showed that words that have many orthographic neighbors sharing the same initial letters ("lead neighbors") facilitated lexical decision more than words with few lead neighbors. This effect did not apply to end neighbors (orthographic neighbors sharing the same final letters). Crucially, rTMS over the RH impaired lead-, but not end-neighborhood facilitation. The results support the split-fovea theory, where the RH has primacy in representing lead neighbors of a written word.

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.

The effect of clause wrap-up on eye movements during reading

The effect of clause wrap-up on eye movements in reading was examined. Readers read passages in which a target category noun referred to either a high typical or a low typical antecedent. In addition, the category noun was either clause final or non-clause final. There were four primary results: (1) Readers looked longer at a category noun when its antecedent was a low typical member of the category than when it was a high typical member; (2) readers looked longer at the category noun and at the post-category region when they were clause final than when they were not clause final; (3) readers regressed from a category noun or post-category region more frequently when it was clause final than when it was not clause final; and (4) readers made longer initial saccades when their eyes left the category noun or post-category region when this word was in clause final position than when it was not clause final. The last result suggests that sometimes higher order processes that are related to making a decision about when to move the eyes impinge on lower level decisions that are typically associated with deciding where to move the eyes.

'The-skipping' revisited in French: programming saccades to skip the article 'les'

Three experiments were performed to verify O'Regan's (1979) [Perception & Psychophysics, 25 (6), 501-509] finding that in reading, the eye moves further forward when going towards the word 'THE' than when going towards a three-letter verb. The experiments were performed in French instead of English, and compared the plural article 'les' with different three-letter verbs. It was confirmed that the eye did indeed move about 1.5 letters further in the case of the article 'les'. Further investigation of the phenomenon suggested that the effect was present even when the prior fixation duration was short: Only when prior fixation was around 200 ms or less, and additionally when the eye started from a launch position that was far from the word, was there a suggestion that the 'les'-skipping effect disappeared.

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

To determine the role of ongoing processing on eye guidance in reading, two studies examined the effects of semantic context on the eyes' initial landing position in words of different levels of processing difficulty. Results from both studies clearly indicate a shift of the initial fixation location towards the end of the words for words that can be predicted from a prior semantic context. However, shifts occur only in high-frequency words and with prior fixations close to the beginning of the target word. These results suggest that ongoing perceptual and linguistic processes can affect the decision of where to send the eyes next in reading. They are explained in terms of the easiness of processing associated with the target words when located in parafoveal vision. It is concluded that two critical factors might help observing effects of linguistic variables on initial landing sites, namely, the frequency of the target word and the position where the eyes are launched from as regards to the beginning of the target word. Results also provide evidence for an early locus of semantic context effects in reading.

Saccadic eye movements and cognition

Scanning of the visual scene is an important selective process in visual perception. In this article we argue that eye-movement data provide an excellent on-line indication of the cognitive processes underlying visual search and reading. We outline some recent advances from physiological investigations of saccadic eye-movement control before focusing on eye-movement behaviour in visual search and reading studies. We consider factors that can affect the duration of fixations and the choice of saccade targets, emphasising continuities between biological and cognitive descriptions. We discuss different ways of measuring cognitive processing time from an eye-movement record and the relationship between attention and eye movements.

Orthographic codes are used in integrating information from the parafovea by the saccadic computation system

Two experiments that examined the characteristics of information extracted from a parafoveal letter string by the saccadic system are reported. In Experiment 1, we observed the effect of the orthographic legality of the initial letter sequence on landing positions. The deviation of landing positions towards an orthographically illegal letter sequence was shown to occur in saccades when subjects were instructed to read a nonsense letter string. Moreover, it was shown that the initial placement of the eyes is influenced by the frequency of occurrence of the letter sequence and not by the frequency of the letters that formed this sequence. Experiment 2 followed up on the implication that readers use orthographic information only from the initial letters of the parafoveal string. We concluded that the saccadic computation system integrates orthographic information from the two initial letters.

Latency dependence of word-initial letter integration by the saccadic system

Two experiments are reported in which saccadic eye movements were examined when the eyes moved to words in which the properties of the word-initial letters differed. It was found that the effect of saccade latency on landing position depended on the properties of the word-initial letters. Under short saccade latencies, landing positions deviated toward the word beginning in the presence of orthographically irregular/informative beginning (OI/IB) letters. This result is interpreted as an influence of the orthographic encoding process that has detected an unusual letter grouping. With longer saccade latencies, an increase of the saccade size was observed for OI/IB words, whereas orthographically regular/uninformative beginning words did not show the effect. It is suggested that this may be a consequence of the dynamics of parafoveal word information processing.