Papers by Sandro Bettella
Visual Cognition 10(2):233-255, 2003
Change blindness is a failure to detect a change in an scene when the change occurs along with so... more Change blindness is a failure to detect a change in an scene when the change occurs along with some visual disturbances. Disturbances are thought to play a delocalizing role that affects the saliency of the “target” transient signal coming from the change location, which would otherwise capture attention and render the change visible. For instance, it is hypothesized that the appearance of new objects in the “mudsplashes” paradigm generates transient signals that compete with the target object's transient signal for attracting attention. Thus, experiments using the mudsplashes paradigm do not rule out a possible role of object changes in capturing attention. Here, by reversing image contrast polarity, we develop a new paradigm to produce change blindness when a real global transient signal is the only visual event occurring, with no edges added or deleted except in the target object. The results show that transient signals, per se, are able to prevent change detection. However, abrupt transients are not necessary if object change occurs in the zero-contrast phase of a smoothly fading and reappearing image, leaving attention as the only common factor affecting all cases of change blindness.
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Oxford Scholarship Online
This chapter discusses a distortion in the perception of straightness not with reference to a lin... more This chapter discusses a distortion in the perception of straightness not with reference to a line but to a contour formed by a sequence of aligned angles, such as those forming the borders of Chinese lanterns. An outline contour may appear to deviate from straightness when the contrast sign along the contour inverts. These local distortions may be observed with a jagged contour as well. This chapter provides some demonstrations in which regular rectangles contoured by a sawtooth borders appear to periodically contract/expand in synch with the phases of luminance variation of surfaces or borders. To explain these phenomena, we need to call into cause a large spatial range of interpolation of the local distortions along the contour.
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Http Dx Doi Org 10 1080 713756677, Oct 18, 2010
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Giornale Italiano Di Psicologia, 1999
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Perception, 2011
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Journal of Vision, 2011
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Journal of Environmental Psychology, 2010
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Perception, 2011
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Perception, 2011
We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in ... more We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity ones (CP rule), has been used to explain several visual illusions. In three experiments we investigated how the binding effect is influenced by luminance contrast value, relatability of contour elements, and distance among them. Experiment 1 showed that the effect was indeed present only when the CP rule was satisfied, and found it to be stronger when the luminance contrast values of the elements are more similar. In experiment 2 the illusion was reported only with relatable edges, and its strength was modulated by the degree of relatability. The CP-rule effectiveness, thus, seems to depend on good continuation. The intensity of contrast polarity signals propagating from an oriented contour might be the less intense, the more its direction deviates from linearity. In experiment 3 we estimated the distance threshold and found it to be smaller than the one found for other illusions, arising with collinear fragments. This seems to show that the reach of the contrast polarity signal inside the association field of a contour unit is shorter along non-collinear orientations than along collinear ones.
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Perception, 2011
We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in ... more We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity ones (CP rule), has been used to explain several visual illusions. In three experiments we investigated how the binding effect is influenced by luminance contrast value, relatability of contour elements, and distance among them. Experiment 1 showed that the effect was indeed present only when the CP rule was satisfied, and found it to be stronger when the luminance contrast values of the elements are more similar. In experiment 2 the illusion was reported only with relatable edges, and its strength was modulated by the degree of relatability. The CP-rule effectiveness, thus, seems to depend on good continuation. The intensity of contrast polarity signals propagating from an oriented contour might be the less intense, the more its direction deviates from linearity. In experiment 3 we estimated the distance threshold and found it to be smaller than the one found for other illusions, arising with collinear fragments. This seems to show that the reach of the contrast polarity signal inside the association field of a contour unit is shorter along non-collinear orientations than along collinear ones.
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Visual cognition, 2004
We report lexical decision experiments in which eye movements and lexical decision time were anal... more We report lexical decision experiments in which eye movements and lexical decision time were analysed. The results show that nonwords produced more fixation than words, and that the time to make a lexical decision was also greater for nonwords. Further, a preview of the ...
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Journal of Environmental Psychology, 2010
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Visual Cognition, 2003
... The ``geon'' theory (Hummel & Biederman, 1992), for instance, codes real-world ... more ... The ``geon'' theory (Hummel & Biederman, 1992), for instance, codes real-world objects as groupings of simple geometric solids such as cylinders and blocks, not as specific contrast ... There was a strong change blindness both on valid cued trials and on invalid cued trials. ...
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Perception, 2011
We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in ... more We studied a novel illusion of tilt inside checkerboards due to the role of contrast polarity in contour integration. The preference for binding of oriented contours having same contrast polarity, over binding of opposite polarity ones (CP rule), has been used to explain several visual illusions. In three experiments we investigated how the binding effect is influenced by luminance contrast value, relatability of contour elements, and distance among them. Experiment 1 showed that the effect was indeed present only when the CP rule was satisfied, and found it to be stronger when the luminance contrast values of the elements are more similar. In experiment 2 the illusion was reported only with relatable edges, and its strength was modulated by the degree of relatability. The CP-rule effectiveness, thus, seems to depend on good continuation. The intensity of contrast polarity signals propagating from an oriented contour might be the less intense, the more its direction deviates from linearity. In experiment 3 we estimated the distance threshold and found it to be smaller than the one found for other illusions, arising with collinear fragments. This seems to show that the reach of the contrast polarity signal inside the association field of a contour unit is shorter along non-collinear orientations than along collinear ones.
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Papers by Sandro Bettella