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Tom Foulsham, Robert Teszka, Alan Kingstone; What is the shape of the visual information that drives saccades in natural images? Evidence from a gaze-contingent display. Journal of Vision 2010;10(7):534. doi: 10.1167/10.7.534.
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© ARVO (1962-2015); The Authors (2016-present)
The decision of where to move the eyes in natural scenes is influenced by both image features and the task at hand. Here, we consider how the information at fixation affects some of the biases typically found in human saccades. In an encoding task, people tend to show a predominance of horizontal saccades. Fixations are often biased towards the centre of the image, and saccade amplitudes show a characteristic distribution. How do these patterns change when peripheral regions are masked or blurred in a gaze-contingent moving window paradigm? In two experiments we recorded eye movements while observers inspected natural scenes in preparation for a recognition test. We manipulated the shape of a window of preserved vision at fixation: features inside the window were intact; peripheral background was either completely masked (Experiment 1) or blurred (Experiment 2). The foveal window was square, or rectangular or elliptical, with more preserved information either horizontally or vertically. If saccades function to increase the new information gained on each fixation, a horizontal window should lead to more vertical saccades and vice versa. In fact, we found the opposite pattern: vertical windows led to more vertical saccades, and horizontal windows were more similar to normal, unconstrained viewing. The shape of the window also affected fixation and amplitude distributions. These results suggest that saccades are influenced by the features currently being processed, rather than by a desire to reveal new information, and that in normal vision these features are sampled from a horizontally elongated region. The eyes would rather continue to explore a partially seen region than launch into the unknown.
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