Scaling of Horizontal and Vertical Fixational Eye Movements

Eye movements during fixation of a stationary target prevent the adaptation of the photoreceptors to continuous illumination and inhibit fading of the image. These random, involuntary, small, movements are restricted at long time scales so as to keep the target at the center of the field of view. Here we use the Detrended Fluctuation Analysis (DFA) in order to study the properties of fixational eye movements at different time scales. Results show different scaling behavior between horizontal and vertical movements. When the small ballistics movements, i.e. micro-saccades, are removed, the scaling exponents in both directions become similar. Our findings suggest that micro-saccades enhance the persistence at short time scales mostly in the horizontal component and much less in the vertical component. This difference may be due to the need of continuously moving the eyes in the horizontal plane, in order to match the stereoscopic image for different viewing distance.Comment: 5 pages, 4 figure

Word frequency in fast priming: Evidence for immediate cognitive control of eye movements during reading

Numerous studies have demonstrated effects of word frequency on eye movements during reading, but the precise timing of this influence has remained unclear. The fast priming paradigm (Sereno & Rayner, 1992) was previously used to study influences of related versus unrelated primes on the target word. Here, we used this procedure to investigate whether the frequency of the prime word has a direct influence on eye movements during reading when the prime-target relation is not manipulated. We found that with average prime intervals of 32 ms readers made longer single fixation durations on the target word in the low than in the high frequency prime condition. Distributional analyses demonstrated that the effect of prime frequency on single fixation durations occurred very early, supporting theories of immediate cognitive control of eye movements. Finding prime frequency effects only 207 ms after visibility of the prime and for prime durations of 32 ms yields new time constraints for cognitive processes controlling eye movements during reading. Our variant of the fast priming paradigm provides a new approach to test early influences of word processing on eye movement control during reading

Is preview benefit from word n + 2 a common effect in reading Chinese? Evidence from eye movements

Although most studies of reading English (and other alphabetic languages) have indicated that readers do not obtain preview benefit from word n + 2, Yang, Wang, Xu, and Rayner (2009) reported evidence that Chinese readers obtain preview benefit from word n + 2. However, this effect may not be common in Chinese because the character prior to the target word in Yang et al.’s experiment was always a very high frequency function word. In the current experiment, we utilized a relatively low frequency word n + 1 to examine whether an n + 2 preview benefit effect would still exist and failed to find any preview benefit from word n + 2. These results are consistent with a recent study which indicated that foveal load modulates the perceptual span during Chinese reading (Yan, Kliegl, Shu, Pan, & Zhou, 2010). Implications of these results for models of eye movement control are discussed

Parafoveal preview effects from word N+1 and word N+2 during reading: A critical review and Bayesian meta-analysis

The use of gaze-contingent display techniques to study reading has shown that readers attend not only to the currently fixated word, but also to the word to the right of the current fixation. However, a critical look at the literature shows that there are a number of questions that cannot be readily answered from the available literature reviews on the topic. First, there is no consensus on whether readers also attend to the second word to the right of fixation. Second, it is not clear whether parafoveal processing is more efficient in languages such as Chinese. Third, it is not well understood whether the measured effects are confounded by the properties of the parafoveal mask. The present study addressed these issues by performing a Bayesian meta-analysis of 93 experiments that used the boundary paradigm (Rayner, 1975). There were three main findings: 1) the advantage of previewing the second word to the right is modest in size and likely not centred on zero; 2) Chinese readers seem to make a more efficient use of parafoveal processing, but this is mostly evident in gaze duration; 3) there are interference effects associated with using different parafoveal masks that roughly increase when the mask is less word-like

Effects of syntactic context on eye movements during reading

Previous research has demonstrated that properties of a currently fixated word and of adjacent words influence eye movement control in reading. In contrast to such local effects, little is known about the global effects on eye movement control, for example global adjustments caused by processing difficulty of previous sentences. In the present study, participants read text passages in which voice (active vs. passive) and sentence structure (embedded vs. non-embedded) were manipulated. These passages were followed by identical target sentences. The results revealed effects of previous sentence structure on gaze durations in the target sentence, implying that syntactic properties of previously read sentences may lead to a global adjustment of eye movement control

Distracting the Mind Improves Performance: An ERP Study

When a second target (T2) is presented in close succession of a first target (T1), people often fail to identify T2, a phenomenon known as the attentional blink (AB). However, the AB can be reduced substantially when participants are distracted during the task, for instance by a concurrent task, without a cost for T1 performance. The goal of the current study was to investigate the electrophysiological correlates of this paradoxical effect.Participants successively performed three tasks, while EEG was recorded. The first task (standard AB) consisted of identifying two target letters in a sequential stream of distractor digits. The second task (grey dots task) was similar to the first task with the addition of an irrelevant grey dot moving in the periphery, concurrent with the central stimulus stream. The third task (red dot task) was similar to the second task, except that detection of an occasional brief color change in the moving grey dot was required. AB magnitude in the latter task was significantly smaller, whereas behavioral performance in the standard and grey dots tasks did not differ. Using mixed effects models, electrophysiological activity was compared during trials in the grey dots and red dot tasks that differed in task instruction but not in perceptual input. In the red dot task, both target-related parietal brain activity associated with working memory updating (P3) as well as distractor-related occipital activity was significantly reduced.The results support the idea that the AB might (at least partly) arise from an overinvestment of attentional resources or an overexertion of attentional control, which is reduced when a distracting secondary task is carried out. The present findings bring us a step closer in understanding why and how an AB occurs, and how these temporal restrictions in selective attention can be overcome

My Hand or Yours? Markedly Different Sensitivity to Egocentric and Allocentric Views in the Hand Laterality Task

In the hand laterality task participants judge the handedness of visually presented stimuli – images of hands shown in a variety of postures and views - and indicate whether they perceive a right or left hand. The task engages kinaesthetic and sensorimotor processes and is considered a standard example of motor imagery. However, in this study we find that while motor imagery holds across egocentric views of the stimuli (where the hands are likely to be one's own), it does not appear to hold across allocentric views (where the hands are likely to be another person's). First, we find that psychophysical sensitivity, d', is clearly demarcated between egocentric and allocentric views, being high for the former and low for the latter. Secondly, using mixed effects methods to analyse the chronometric data, we find high positive correlation between response times across egocentric views, suggesting a common use of motor imagery across these views. Correlations are, however, considerably lower between egocentric and allocentric views, suggesting a switch from motor imagery across these perspectives. We relate these findings to research showing that the extrastriate body area discriminates egocentric (‘self’) and allocentric (‘other’) views of the human body and of body parts, including hands