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Simon P Liversedge

Publications and source records attributed to Simon P Liversedge.

At least 19 recordsLinked to original sources
PubMed2006

Binocular coordination of the eyes during reading.

Saccadic eye movements and fixations are the behavioral means by which we visually sample text during reading. Human oculomotor control is governed by a complex neurophysiological system involving the brain stem, superior colliculus, and several cortical areas. A very widely held belief among researchers investigating primate vision is that the oculomotor system serves to orient the visual axes of both eyes to fixate the same target point in space. It is argued that such precise positioning of the eyes is necessary to place images on corresponding retinal locations, such that on each fixation a single, nondiplopic, visual representation is perceived. Vision works actively through a continual sampling process involving saccades and fixations. Here we report that during normal reading, the eyes do not always fixate the same letter within a word. We also demonstrate that saccadic targeting is yoked and based on a unified cyclopean percept of a whole word since it is unaffected if different word parts are delivered exclusively to each eye via a dichoptic presentation technique. These two findings together suggest that the visual signal from each eye is fused at a very early stage in the visual pathway, even when the fixation disparity is greater than one character (0.29 deg), and that saccade metrics for each eye are computed on the basis of that fused signal.

Fixation, Ocular↗
PubMed2006

The binocular coordination of eye movements during reading in children and adults.

Recent evidence indicates that each eye does not always fixate the same letter during reading and there has been some suggestion that processing difficulty may influence binocular coordination. We recorded binocular eye movements from children and adults reading sentences containing a word frequency manipulation. We found disparities of significant magnitude between the two eyes for all participants, with greater disparity magnitudes in children than adults. All participants made fewer crossed than uncrossed fixations. However, children made a higher proportion of crossed fixations than adults. We found no influence of word frequency on children's fixations and on binocular coordination in adults.

Adolescent↗
PubMed2006

Binocular coordination of eye movements during reading.

Binocular coordination of the eyes during reading was examined. Fixation disparity greater than one character occurred on 47% of fixations, with the disparity being predominantly uncrossed (39%), though a small proportion of fixations were crossed. The average magnitude of disparity, measured at the end of fixation, was 1.1 characters for all fixations. For the 47% of non-aligned fixations the average magnitude of disparity was 1.9 characters. Vergence movements that reduced fixation disparity occurred during fixations, and their magnitude was positively correlated with fixation duration. Finally, eye dominance did not modulate fixation disparity magnitude or the proportion of disparate fixations.

Dominance, Ocular↗
PubMed2006

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.

Eye Movements↗
PubMed2006

Binocular coordination of the eyes during reading: word frequency and case alternation affect fixation duration but not fixation disparity.

This experiment investigated whether properties of the text being read affect binocular coordination of the eyes during reading. Readers' binocular eye movements were recorded while they read sentences that contained high- and low-frequency words. In addition, half of the sentences were presented in normal case, and half were presented in alternating case (i.e., AlTeRnAtInG cAsE). Past research has suggested that the visual system tolerates less binocular fixation disparity with alternating than with normal case (Heller & Radach, 1999). While both word frequency and alternating case produced large effects on fixation durations on the target word, neither manipulation affected the magnitude of fixation disparity. It is concluded that linguistic and visual properties of the text being read do not influence binocular coordination of the eyes during reading. Additional analyses also showed no difference in fixation disparity between reading and a nonlinguistic task. Implications of these results for split-fovea models of reading are discussed.

Analysis of Variance↗
PubMed2006

Change blindness and the primacy of object appearance.

A large body of work suggests that the visual system is particularly sensitive to the appearance of new objects. This is based partly on evidence from visual search studies showing that onsets capture attention whereas many other types of visual event do not. Recently, however, the notion that object onset has a special status in visual attention has been challenged. For instance, an object that looms toward an observer has also been shown to capture attention. In two experiments, we investigated whether onset receives processing priority over looming. Observers performed a change detection task in which one of the display objects either loomed or receded, or a new object appeared. Results showed that looming objects were more resistant to change blindness than receding objects. Crucially, however, the appearance of a new object was less susceptible to change blindness than both looming and receding. We argue that the visual system is particularly sensitive to object onsets.

Attention↗
PubMed2005

Foveal processing difficulty does not modulate non-foveal orthographic influences on fixation positions.

Two experiments show that eye fixations land nearer to the beginning of misspelled than correctly spelled beginning words during sentence reading. The effect holds regardless of whether the previous word is easy (high frequency) or difficult (low frequency) to process. In Experiment 1, the misspelled words were directly fixated. In Experiment 2, a saccade contingent change technique was used such that the words were always correctly spelled once they were fixated. The results show that non-foveal orthography influences where words are first fixated regardless of foveal processing load.

Attention↗
PubMed2005

Eye movements when reading disappearing text: the importance of the word to the right of fixation.

In a series of experiments, the currently fixated word (word n) and/or the word to the right of fixation (word n+1) either disappeared or was masked during readers' eye fixations. Consistent with prior research, when only word n disappeared or was masked, there was little disruption to reading. However, when word n+1 either disappeared or was masked (either at the onset of fixation on word n or after 60 ms), there was considerable disruption to reading. Independent of whether word n and/or word n+1 disappeared or was masked, there were robust frequency effects on the fixation on word n. These results not only confirm the robust influence of cognitive/linguistic processing on fixation times in reading, but also again confirm the importance of preprocessing the word to the right of fixation for fluent reading.

Fixation, Ocular↗
PubMed2005

The influence of parafoveal word length and contextual constraint on fixation durations and word skipping in reading.

The present study examined the relationship between the predictability of words within a sentence and the availability of parafoveal word length information, on when and where the eyes move in reading. Predictability influenced first-pass reading times when parafoveal word length preview information was correct, but not when it was incorrect. Similarly, for saccades launched from near the target word (word n), predictability influenced the probability with which it was skipped only when the word length preview was correct. By contrast, for saccades launched farther away from word n, predictability influenced word skipping regardless of the parafoveal word length preview. Taken together, the data suggest that parafoveal word length preview and predictability can act as a joint constraint on the decision of when and where to move the eyes.

Eye Movements↗
PubMed2005

Eye movements and the modulation of parafoveal processing by foveal processing difficulty: A reexamination.

Henderson and Ferreira (1990) found that foveal load (manipulated via word frequency) modulates parafoveal processing, thereby affecting the amount of preview benefit obtained from the word to the right of fixation. The present experiment used the eye-contingent boundary paradigm and, consistent with Henderson and Ferreira, showed that foveal load modulated preview benefit for participants who were not aware of the display changes during reading. Also, for these participants, foveal load modulated preview benefit regardless of fixation durations on the foveal word. For participants who were aware of the display change, preview benefits occurred regardless of foveal processing difficulty. These results have important implications for understanding the way in which foveal load influences parafoveal processing during reading.

Eye Movements↗
PubMed2004

Eye movements when reading disappearing text: is there a gap effect in reading?

Readers' eye movements were monitored when they read either normal sentences or sentences with masked or disappearing text (in which the fixated word disappeared or was masked after 60 ms). The goals of the research were to investigate (1) whether a gap effect occurred in reading and (2) the influence of linguistic and visual factors on oculomotor control. The results of a number of global analyses of eye movements under disappearing text conditions clearly demonstrated that there is no gap effect in reading. However, comparative analyses across a number of local measures in the experiments indicated that cognitive/lexical processes, as well as the continual uptake of visual information, influence eye movement control during reading. A persistent visual object throughout fixation caused refixations and even when a fixated word had disappeared (or been masked), there were significant effects of word frequency and word length.

Cognition↗
PubMed2004

The effect of plausibility on eye movements in reading.

Readers' eye movements were monitored as they read sentences describing events in which an individual performed an action with an implement. The noun phrase arguments of the verbs in the sentences were such that when thematic assignment occurred at the critical target word, the sentence was plausible (likely theme), implausible (unlikely theme), or anomalous (an inappropriate theme). Whereas the target word in the anomalous condition provided evidence of immediate disruption, the effect of the target word in the implausible condition was considerably delayed. The results thus indicate that when a word is anomalous, it has an immediate effect on eye movements, but that the effect of implausibility is not as immediate.

Attitude↗
PubMed2004

Processing doubly quantified sentences: evidence from eye movements.

We investigated the processing of doubly quantified sentences, such as KeUy showed a photo to every critic, that are ambiguous as to whether the indefinite (a photo) specifies single or multiple referents. Ambiguity resolution requires the computation of relative quantifier scope: Whether a or every takes wide scope, thereby determining how many entities or events are to be represented. In an eye-tracking experiment, we manipulated quantifier order and whether continuations were singular or plural, for constructions with the direct or the indirect object occurring first. We obtained effects consistent with the on-line processing of relative scope at the doubly quantified phrase and considered two possible explanations for a preference for singular continuations to the quantified sentence. We conclude that relative quantifier scope is computed on line during reading but may not be a prerequisite for the resolution of definite anaphors, unless required by secondary tasks.

Eye Movements↗
PubMed2003

Children's comprehension of sentences with focus particles.

We report three studies investigating children's and adults' comprehension of sentences containing the focus particle only. In Experiments 1 and 2, four groups of participants (6-7 years, 8-10 years, 11-12 years and adult) compared sentences with only in different syntactic positions against pictures that matched or mismatched events described by the sentence. Contrary to previous findings (Crain, S., Ni, W., & Conway, L. (1994). Learning, parsing and modularity. In C. Clifton, L. Frazier, & K. Rayner (Eds.), Perspectives on sentence processing. Hillsdale, NJ: Lawrence Erlbaum; Philip, W., & Lynch, E. (1999). Felicity, relevance, and acquisition of the grammar of every and only. In S. C. Howell, S. A. Fish, & T. Keith-Lucas (Eds.), Proceedings of the 24th annual Boston University conference on language development. Somerville, MA: Cascadilla Press) we found that young children predominantly made errors by failing to process contrast information rather than errors in which they failed to use syntactic information to restrict the scope of the particle. Experiment 3 replicated these findings with pre-schoolers.

Adult↗
PubMed2003

The influence of morphological information on cataphoric pronoun assignment.

In 3 eye-tracking experiments, the authors investigated the use of morphological information during pronoun resolution. Experiments 1 and 2 showed that disruption occurred when a preferred assignment was inconsistent with gender information. Experiment 2 ensured that this difficulty was not due to the introduction of a new discourse entity. Experiment 3 showed that disruption also occurred when number information was inconsistent with the preferred assignment. The results indicate that the use of morphological information is delayed until after the computation of coreference relations.

Eye Movements↗
PubMed2003

Reading disappearing text: cognitive control of eye movements.

Participants read sentences containing high- or low-frequency target words under normal reading conditions or disappearing-text conditions (in which the word that was fixated disappeared after 60 ms). Even though the fixated word had disappeared after 60 ms, there was still a robust frequency effect wherein readers fixated longer on low-frequency words than on high-frequency words. Thus, the results are consistent with cognitive-control models of eye movement control and inconsistent with visual/oculomotor-control models. Although the uptake of visual information is clearly important for reading, it is the cognitive processes associated with understanding the fixated words that drive the eyes through the text.

Adolescent↗
PubMed2003

Thematic processing of adjuncts: evidence from an eye-tracking experiment.

We investigated thematic processing in sentences containing a prepositional phrase that was ambiguous between a locative and a temporal interpretation. We manipulated context (temporal or locative), target sentence (temporal or locative), and whether or not the main verb of the target and the context was repeated. Results showed that context dictated the participants' thematic expectations. Thematically, congruent target and context pairs were read faster than incongruent pairs. This effect was not modulated by verb repetition. We argue that wh-words cause readers to lodge semantically vacuous thematic roles in their discourse representation that bias a reader's interpretation of subsequent thematically ambiguous adjuncts in their discourse representation.

Eye Movements↗