Stoyan Kurtev

Re-evaluating split-fovea processing in word recognition: effects of fixation location within words.

It has been claimed that word recognition is affected fundamentally by the precise location at which a word is fixated because a precise split in hemispheric processing at the point of fixation causes all letters to the left and right of fixation to project to different, contralateral hemispheres. To assess this claim, 5-letter words (and nonwords) were presented for lexical decision when participants fixated the space immediately to the left (location 1) or right (location 6) of each stimulus, or one of the four possible inter-letter spaces (locations 2-5). Fixation location was controlled using an eye-tracker linked to a fixation-contingent display and all stimuli were presented entirely within foveal vision to avoid confounding influences of extrafoveal hemispheric projections. Performance was equally poorest when fixating locations 1 and 6 (when words were shown entirely to either the right and left of fixation), intermediate for location 5, and equally superior for locations 2, 3, and 4. Additional word-specific analyses also showed no evidence of the effects of fixation location on optimal word recognition predicted by split-fovea processing. These findings suggest that, while fixation location influences word recognition, word recognition is apparently not affected by a split in hemispheric processing at the point of fixation and does not depend critically on the precise location at which a word is fixated. Implications of these findings for the role of fixation location in word recognition are discussed.

An ERP Assessment of Hemispheric Projections in Foveal and Extrafoveal Word Recognition

Background The existence and function of unilateral hemispheric projections within foveal vision may substantially affect foveal word recognition. The purpose of this research was to reveal these projections and determine their functionality. Methodology Single words (and pseudowords) were presented to the left or right of fixation, entirely within either foveal or extrafoveal vision. To maximize the likelihood of unilateral projections for foveal displays, stimuli in foveal vision were presented away from the midline. The processing of stimuli in each location was assessed by combining behavioural measures (reaction times, accuracy) with on-line monitoring of hemispheric activity using event-related potentials recorded over each hemisphere, and carefully-controlled presentation procedures using an eye-tracker linked to a fixation-contingent display. Principal Findings Event-related potentials 100–150 ms and 150–200 ms after stimulus onset indicated that stimuli in extrafoveal and foveal locations were projected unilaterally to the hemisphere contralateral to the presentation hemifield with no concurrent projection to the ipsilateral hemisphere. These effects were similar for words and pseudowords, suggesting this early division occurred before word recognition. Indeed, event-related potentials revealed differences between words and pseudowords 300–350 ms after stimulus onset, for foveal and extrafoveal locations, indicating that word recognition had now occurred. However, these later event-related potentials also revealed that the hemispheric division observed previously was no longer present for foveal locations but remained for extrafoveal locations. These findings closely matched the behavioural finding that foveal locations produced similar performance each side of fixation but extrafoveal locations produced left-right asymmetries. Conclusions These findings indicate that an initial division in unilateral hemispheric projections occurs in foveal vision away from the midline but is not apparent, or functional, when foveal word recognition actually occurs. In contrast, the division in unilateral hemispheric projections that occurs in extrafoveal locations is still apparent, and is functional, when extrafoveal word recognition takes place.

Re-evaluating split-fovea processing in word recognition: effects of word length during monocular viewing

Several studies have claimed that, when fixating a word, a precise split in foveal processing causes all letters to the left and right of fixation to project to different, contralateral hemispheres (split-fovea theory--SFT). In support of this claim, Lavidor et al. (2001; hereafter LES&B) reported that lexical decisions were affected by the number of letters to the left of fixation but not the right, and that this indicates a functional division in hemispheric processing at the point of fixation. Jordan, Paterson, and Stachurski (Cortex, 2009; hereafter JP&S) re-evaluated these claims over 3 experiments using LES&Bs original stimuli and procedures and found no support for the findings of LES&B. Following LES&B, JP&S presented stimuli binocularly (i.e., as in normal viewing). However, this procedure has its own complications for SFT (and for assessing the validity of the theory) because the two eyes often do not fixate the same location. Consequently, we report two further experiments which used an eye-tracker to ensure fixation accuracy and monocular viewing to eliminate influences of fixation disparity. Experiment 1 used the same-sized typeface as JP&S, and Experiment 2 used a larger typeface to approximate normal reading size. In line with the findings of JP&S, neither experiment could replicate the findings of LES&B and both experiments showed simply that word recognition was easier when fixations were made towards the beginning of words. Thus, after a total of 5 separate experiments, using binocular and monocular viewing conditions and stimuli presented in a range of sizes, none of these experiments has been able to replicate the findings of LES&B or provide any evidence for a functional division in hemispheric processing at the point of fixation.

Binocular Fixation Disparity in Single Word Displays.

It has been claimed that the recognition of words displayed in isolation is affected by the precise location at which they are fixated. However, this putative role for fixation location has yet to be reconciled with the finding from reading research that binocular fixations are often misaligned and, therefore, more than 1 location in a word is often fixated simultaneously. The accuracy and alignment of binocular fixations during single word processing have not been assessed previously. To investigate this issue, words were presented for lexical decision at locations around a central fixation point. Eye-tracking data revealed that participants often fixated inaccurately and that fixations were frequently misaligned, but that this did not affect word recognition. The findings show that binocular fixation disparity is pervasive even in single word displays and a potential source of confound for research into effects of fixation location on word recognition.

Reevaluating split-fovea processing in word recognition: hemispheric dominance, retinal location, and the word-nonword effect.

Many studies have claimed that hemispheric projections are split precisely at the foveal midline and so hemispheric asymmetry affects word recognition right up to the point of fixation. To investigate this claim, four-letter words and nonwords were presented to the left or right of fixation, either close to fixation in foveal vision or farther from fixation in extrafoveal vision. Presentation accuracy was controlled using an eyetracker linked to a fixation-contingent display. Words presented foveally produced identical performance on each side of fixation, but words presented extrafoveally showed a clear left-hemisphere (LH) advantage. Nonwords produced no evidence of hemispheric asymmetry in any location. Foveal stimuli also produced an identical word-nonword effect on each side of fixation, whereas extrafoveal stimuli produced a word-nonword effect only for LH (not right-hemisphere) displays. These findings indicate that functional unilateral projections to contralateral hemispheres exist in extrafoveal locations but provide no evidence of a functional division in hemispheric processing at fixation.

Do fixation cues ensure fixation accuracy in split-fovea studies of word recognition?

Many studies have claimed that hemispheric processing is split precisely at the foveal midline and so place great emphasis on the precise location at which words are fixated. These claims are based on experiments in which a variety of fixation procedures were used to ensure fixation accuracy but the effectiveness of these procedures is unclear. We investigated this issue using procedures matched to the original studies and an eye-tracker to monitor the locations actually fixated. Four common types of fixation cues were used: cross, two vertical gapped lines, two vertical gapped lines plus a secondary task in which a digit was presented at the designated fixation point, and a dot. Accurate fixations occurred on <35% of trials for all fixation conditions. Moreover, despite the usefulness often attributed to a secondary task, no increase in fixation accuracy was produced in this condition. The indications are that split-fovea theory should not assume that fixation of specified locations occurs in experiments without appropriate eye-tracking control or, indeed, that consistent fixation of specified locations is plausible under normal conditions of word recognition.

A further look at postview effects in reading: An eye-movements study of influences from the left of fixation.

When reading from left to right, useful information acquired during each fixational pause is widely assumed to extend 14 to 15 characters to the right of fixation but just 3 to 4 characters to the left, and certainly no further than the beginning of the fixated word. However, this leftward extent is strikingly small and seems inconsistent with other aspects of reading performance and with the general horizontal symmetry of visual input. Accordingly, 2 experiments were conducted to examine the influence of text located to the left of fixation during each fixational pause using an eye-tracking paradigm in which invisible boundaries were created in sentence displays. Each boundary corresponded to the leftmost edge of each word so that, as each sentence was read, the normal letter content of text to the left of each fixated word was corrupted by letter replacements that were either visually similar or visually dissimilar to the originals. The proximity of corrupted text to the left of fixation was maintained at 1, 2, 3, or 4 words from the left boundary of each fixated word. In both experiments, relative to completely normal text, reading performance was impaired when each type of letter replacement was up to 2 words to the left of fixated words but letter replacements further from fixation produced no impairment. These findings suggest that key aspects of reading are influenced by information acquired during each fixational pause from much further leftward than is usually assumed. Some of the implications of these findings for reading are discussed.

Myalgic encephalomyelitis/chronic fatigue syndrome patients’ reports of symptom changes following cognitive behavioural therapy, graded exercise therapy and pacing treatments: Analysis of a primary survey compared with secondary surveys:

Cognitive behavioural therapy and graded exercise therapy are promoted as evidence-based treatments for myalgic encephalomyelitis/chronic fatigue syndrome. This article explores patients’ symptom responses following these treatments versus pacing therapy, an approach favoured by many sufferers. We analyse data from a large cross-sectional patient survey (n = 1428) and compare our findings with those from comparable patient surveys (n = 16,665), using a mix of descriptive statistics and regression analysis modelling. Findings from analysis of primary and secondary surveys suggest that cognitive behavioural therapy is of benefit to a small percentage of patients (8%–35%), graded exercise therapy brings about large negative responses in patients (54%–74%), while pacing is the most favoured treatment with the lowest negative response rate and the highest reported benefit (44%–82%).

Fast And Slow Readers And The Effectiveness Of The Spatial Frequency Content Of Text: Evidence From Reading Times And Eye Movements

Text contains a range of different spatial frequencies but the effectiveness of spatial frequencies for normal variations in skilled adult reading ability is unknown. Accordingly, young skilled adult readers showing fast or slow reading ability read sentences displayed as normal or filtered to contain only very low, low, medium, high, or very high spatial frequencies. Reading times and eye movement measures of fixations and saccades assessed the effectiveness of these displays for reading. Reading times showed that, for each reading ability, medium, high, and very high spatial frequencies were all more effective than lower spatial frequencies. Indeed, for each reading ability, reading times for normal text were maintained when text contained only medium, high, or very high spatial frequencies. However, reading times for normal text and for each spatial frequency were all substantially shorter for fast readers than for slow readers, and this advantage for fast readers was similar for normal, medium, high, and very high spatial frequencies but much larger for low and very low spatial frequencies. In addition, fast readers made fewer and shorter fixations, fewer and shorter regressions, and longer forward saccades, than slow readers, and these differences were generally similar in size for normal, medium, high, and very high spatial frequencies, but larger when spatial frequencies were lower. These findings suggest that fast and slow adult readers can each use a range of different spatial frequencies for reading but fast readers make more effective use of these spatial frequencies and especially those that are lower. (PsycINFO Database Record

Effects of Spatial Frequencies on Word Identification by Fast and Slow Readers: Evidence from Eye Movements.

Recent research has shown that differences in the effectiveness of spatial frequencies for fast and slow skilled adult readers may be an important component of differences in reading ability in the skilled adult reading population (Jordan et al., 2016a). But the precise nature of this influence on lexical processing during reading remains to be fully determined. Accordingly, to gain more insight into the use of spatial frequencies by skilled adult readers with fast and slow reading abilities, the present study looked at effects of spatial frequencies on the processing of specific target words in sentences. These target words were of either high or low lexical frequency and each sentence was displayed as normal or filtered to contain only very low, low, medium, high, or very high spatial frequencies. Eye movement behavior for target words was closest to normal for each reading ability when text was shown in medium or higher spatial frequency displays, although reading occurred for all spatial frequencies. Moreover, typical word frequency effects (the processing advantage for words with higher lexical frequencies) were observed for each reading ability across a broad range of spatial frequencies, indicating that many different spatial frequencies provide access to lexical representations during textual reading for both fast and slow skilled adult readers. Crucially, however, target word fixations were fewer and shorter for fast readers than for slow readers for all display types, and this advantage for fast readers appeared to be similar for normal, medium, high, and very high spatial frequencies but larger for low and very low spatial frequencies. Therefore, although fast and slow skilled adult readers can both use a broad range of spatial frequencies when reading, fast readers make more effective use of these spatial frequencies, and especially those that are lower, when processing the identities of words.