Fixation disparity during reading: Fusion, not suppression

In this paper I present a brief review of some recent studies my colleagues and I have carried out to investigate binocular coordination during reading. These studies demonstrate that the eyes are often not perfectly aligned during reading, with fixation disparities of approximately one character on average. Both crossed and uncrossed disparities are common and vergence movements during fixations serve to reduce, but not eliminate disparity. Fixation disparity results in different retinal inputs from each eye, yet a single non diplopic visual representation of the text is perceived when we read. A further experiment, with dichoptically presented target words in normally presented sentence frames, showed that a mechanism of fusion rather than suppression operates at an early stage during visual processing. Saccade metrics appear to be computed according to a unified visual representation based on input from both eyes. based on input from both eyes

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

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

Investigating eye movement acquisition and analysis technologies as a causal factor in differential prevalence of crossed and uncrossed fixation disparity during reading and dot scanning

Previous studies examining binocular coordination during reading have reported conflicting results in terms of the nature of disparity (e.g. Kliegl, Nuthmann, &amp; Engbert (Journal of Experimental Psychology General 135:12-35, 2006); Liversedge, White, Findlay, &amp; Rayner (Vision Research 46:2363-2374, 2006). One potential cause of this inconsistency is differences in acquisition devices and associated analysis technologies. We tested this by directly comparing binocular eye movement recordings made using SR Research EyeLink 1000 and the Fourward Technologies Inc. DPI binocular eye-tracking systems. Participants read sentences or scanned horizontal rows of dot strings; for each participant, half the data were recorded with the EyeLink, and the other half with the DPIs. The viewing conditions in both testing laboratories were set to be very similar. Monocular calibrations were used. The majority of fixations recorded using either system were aligned, although data from the EyeLink system showed greater disparity magnitudes. Critically, for unaligned fixations, the data from both systems showed a majority of uncrossed fixations. These results suggest that variability in previous reports of binocular fixation alignment is attributable to the specific viewing conditions associated with a particular experiment (variables such as luminance and viewing distance), rather than acquisition and analysis software and hardware.<br/

Beyond isolated word recognition

In this commentary we concur with Frost’s view of the centrality of universal principles in models of word identification. However, we argue that other processes in sentence comprehension also fundamentally constrain the nature of written word identification. Furthermore, these processes appear to be universal. We, therefore, argue that universality in word identification should not be considered in isolation, but instead in the context of other linguistic processes that occur during normal reading

Evidence for a reduction of the rightward extent of the perceptual span when reading dynamic horizontally scrolling text

The dynamic horizontally scrolling text format produces a directional conflict in the allocation of attention for reading, with a necessity to track each word leftward (in the direction of movement) concurrently with normal rightward shifts made to progress through the text (in left-to-right orthographies such as English). The gaze-contingent window paradigm was used to compare the extent of the perceptual span in reading of scrolling and static sentences. Across two experiments, this investigation confirmed that the allocation of attentional resources to the right of fixation was compressed with scrolling text. There was no evidence for a reversal of the direction of asymmetry or a confounding shift of landing position.</p

Binocular coordination: reading stereoscopic sentences in depth

The present study employs a stereoscopic manipulation to present sentences in three dimensions to subjects as they read for comprehension. Subjects read sentences with (a) no depth cues, (b) a monocular depth cue that implied the sentence loomed out of the screen (i.e., increasing retinal size), (c) congruent monocular and binocular (retinal disparity) depth cues (i.e., both implied the sentence loomed out of the screen) and (d) incongruent monocular and binocular depth cues (i.e., the monocular cue implied the sentence loomed out of the screen and the binocular cue implied it receded behind the screen). Reading efficiency was mostly unaffected, suggesting that reading in three dimensions is similar to reading in two dimensions. Importantly, fixation disparity was driven by retinal disparity; fixations were significantly more crossed as readers progressed through the sentence in the congruent condition and significantly more uncrossed in the incongruent condition. We conclude that disparity depth cues are used on-line to drive binocular coordination during reading.<br/

Cat and mouse search: the influence of scene and object analysis on eye movements when targets change locations during search

We explored the influence of early scene analysis and visible object characteristics on eye movements when searching for objects in photographs of scenes. On each trial, participants were shown sequentially either a scene preview or a uniform grey screen (250 ms), a visual mask, the name of the target and the scene, now including the target at a likely location. During the participant's first saccade during search, the target location was changed to: (i) a different likely location, (ii) an unlikely but possible location or (iii) a very implausible location. The results showed that the first saccade landed more often on the likely location in which the target re-appeared than on unlikely or implausible locations, and overall the first saccade landed nearer the first target location with a preview than without. Hence, rapid scene analysis influenced initial eye movement planning, but availability of the target rapidly modified that plan. After the target moved, it was found more quickly when it appeared in a likely location than when it appeared in an unlikely or implausible location. The findings show that both scene gist and object properties are extracted rapidly, and are used in conjunction to guide saccadic eye movements during visual search

The FVF framework and target prevalence effects

The Functional Visual Field (FVF) offers explanatory power. To us, it relates to existing literature on the flexibility of attentional focus in visual search and reading (Eriksen &amp; St. James, 1986; McConkie &amp; Rayner, 1975). The target article promotes reflection on existing findings. Here we consider the FVF as a mechanism in the Prevalence Effect in visual search (PE)

Would adults with autism be less likely to bury the survivors?: An eye movement study of anomalous text reading

In a single eye movement experiment, we investigated the effects of context on the time course of local and global anomaly processing during reading in adults with Autism Spectrum Disorder (ASD). In one condition, short paragraph texts contained anomalous target words. Detection of the anomaly was only possible through evaluation of word meaning in relation to the global context of the whole paragraph (Passage-Level Anomalies). In another condition, the anomaly could be detected via computation of a local thematic violation within a single sentence embedded in the paragraph (Sentence-Level Anomalies). For the sentence-level anomalies, the ASD group, in contrast with the typically developing (TD) group, showed early detection of the anomaly as indexed by regressive eye movements from the critical target word upon fixation. Conversely, for the passage-level anomalies, and in contrast with the ASD group, theTD group showed early detection of the anomaly with increased regressive eye movements once the critical word had been fixated. The reversal of the pattern of regression path data for the two groups, for the sentence- and passage-level anomalies, is discussed in relation to cognitive accounts of ASD.</p

Universality in eye movements and reading: a trilingual investigation

Universality in language has been a core issue in the fields of linguistics and psycholinguistics for many years (e.g., Chomsky, 1965). Recently, Frost (2012) has argued that establishing universals of process is critical to the development of meaningful, theoretically motivated, cross-linguistic models of reading. In contrast, other researchers argue that there is no such thing as universals of reading (e.g., Coltheart &amp; Crain, 2012). Reading is a complex, visually mediated psychological process, and eye movements are the behavioural means by which we encode the visual information required for linguistic processing. To investigate universality of representation and process across languages we examined eye movement behaviour during reading of very comparable stimuli in three languages, Chinese, English and Finnish. These languages differ in numerous respects (character based vs. alphabetic, visual density, informational density, word spacing, orthographic depth, agglutination, etc.). We used linear mixed modelling techniques to identify variables that captured common variance across languages. Despite fundamental visual and linguistic differences in the orthographies, statistical models of reading behaviour were strikingly similar in a number of respects, and thus, we argue that their composition might reflect universality of representation and process in reading