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

The Role of Attention in Ambiguous Reversals of Structure-From-Motion

Multiple dots moving independently back and forth on a flat screen induce a compelling illusion of a sphere rotating in depth (structure-from-motion). If all dots simultaneously reverse their direction of motion, two perceptual outcomes are possible: either the illusory rotation reverses as well (and the illusory depth of each dot is maintained), or the illusory rotation is maintained (but the illusory depth of each dot reverses). We investigated the role of attention in these ambiguous reversals. Greater availability of attention – as manipulated with a concurrent task or inferred from eye movement statistics – shifted the balance in favor of reversing illusory rotation (rather than depth). On the other hand, volitional control over illusory reversals was limited and did not depend on tracking individual dots during the direction reversal. Finally, display properties strongly influenced ambiguous reversals. Any asymmetries between ‘front’ and ‘back’ surfaces – created either on purpose by coloring or accidentally by random dot placement – also shifted the balance in favor of reversing illusory rotation (rather than depth). We conclude that the outcome of ambiguous reversals depends on attention, specifically on attention to the illusory sphere and its surface irregularities, but not on attentive tracking of individual surface dots

Target selection for pursuit and saccadic eye movements in humans

Eye movements were recorded from three subjects as they initiated tracking of a small circle (“target”) moving leftward or rightward, above or below the horizontal meridian, either alone or in the presence of a small square (“distractor”) moving leftward or rightward on the other side of the horizontal meridian. At the start of each trial, subjects were provided with either a “form ” cue (always centrally positioned and having the circular shape and color of the upcoming moving target) or a “location ” cue (a small white square positioned where the upcoming target would appear). The latency of pursuit increased in the presence of an oppositely moving distractor when subjects were provided the form cues but not when they were provided the location cues. The latency of saccades showed similar, but smaller, increases when subjects were given the form cues. On many trials with the form cues, pursuit started in the direction of the distractor and then reversed to follow the target. On these trials, the initial saccade often, but not always, also followed the distractor. These results indicate that the mechanisms of target selection for pursuit and saccades are tightly coordinated but not strictly yoked. The shared effects of the distractor on the latencies of pursuit and saccades probably re�ect the common role of visual attention in �ltering the inputs that guide these two types of eye movements. The differences in the details of the effects on pursuit and saccades suggest that the neural mechanisms that trigger these two movements can be independently regulated

Knowledge and attitudes of European Kosher consumers as revealed through focus groups

There is a very small, yet important minority within the community of European Union kosher consumers. There is a great deal of research regarding objective aspects of the kosher religious as well as civil laws and their implementation, but comparatively little research about the subjective attitudes, opinions, and concerns of those who actually purchase and consume kosher food. Such information can be important for a variety of interested parties including suppliers, distributors, regulatory agencies, legislators, and certifying agencies as well as religious authorities. We collected relevant data by organizing hour-long Focus Groups (FG) in five European cities and a suburb of Tel Aviv. The FG addressed consumer attitudes related to shopping practices, commitment, trust, and certification as well as their knowledge and opinions regarding nonhuman animal welfare as it relates to shechita (kosher slaughter) and knowledge of the issue of stunning animals at the time of killing. One of the significant findings was a high level of secularization among Jews that translates to a low level of commitment to eating kosher. But this was accompanied by assertions that eating kosher was an important religious obligation and complaints of low availability and high cost. There was a strong feeling, even among those less committed to eating kosher, that shechita was the preferred method of slaughtering an animal (more animal friendly) and a strong suspicion of anti-Semitism as a motivation for any attempt to impose a stunning obligation