Volume 8, Number 7, Article 5, Pages 1-11 doi:10.1167/8.7.5 http://journalofvision.org/8/7/5/ ISSN 1534-7362
Fixation locations when grasping partly occluded objects
Denise D. J. de Grave
Department of Experimental Psychology, Justus-Liebig-Universität Giessen, Giessen, Germany, & Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands
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Constanze Hesse
Department of Experimental Psychology, Justus-Liebig-Universitat Giessen, Giessen, Germany
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Anne-Marie Brouwer
TNO, Soesterberg, The Netherlands
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Volker H. Franz
Department of Experimental Psychology, Justus-Liebig-Universitat Giessen, Giessen, Germany
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Abstract

When grasping an object, subjects tend to look at the contact positions of the digits (A. M. Brouwer, V. H. Franz, D. Kerzel, & K. R. Gegenfurtner, 2005; R. S. Johansson, G. Westling, A. Bäckström, & J. R. Flanagan, 2001). However, these contact positions are not always visible due to occlusion. Subjects might look at occluded parts to determine the location of the contact positions based on extrapolated information. On the other hand, subjects might avoid looking at occluded parts since no object information can be gathered there. To find out where subjects fixate when grasping occluded objects, we let them grasp flat shapes with the index finger and thumb at predefined contact positions. Either the contact position of the thumb or the finger or both was occluded. In a control condition, a part of the object that does not involve the contact positions was occluded. The results showed that subjects did look at occluded object parts, suggesting that they used extrapolated object information for grasping. Additionally, they preferred to look in the direction of the index finger. When the contact position of the index finger was occluded, this tendency was inhibited. Thus, an occluder does not prevent fixations on occluded object parts, but it does affect fixation locations especially in conditions where the preferred fixation location is occluded.

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History
Received August 10, 2007; published May 20, 2008
Citation
de Grave, D. D. J., Hesse, C., Brouwer, A.-M., & Franz, V. H. (2008). Fixation locations when grasping partly occluded objects. Journal of Vision, 8(7):5, 1-11, http://journalofvision.org/8/7/5/, doi:10.1167/8.7.5.
Keywords
fixations, saccades, eye movements, occlusion, grasping
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