Show Reference: "Differences in fixations between grasping and viewing objects"

Differences in fixations between grasping and viewing objects Journal of Vision, Vol. 9, No. 1. (16 January 2009), doi:10.1167/9.1.18 by Anne-Marie Brouwer, Volker H. Franz, Karl R. Gegenfurtner
@article{brouwer-et-al-2009,
    abstract = {Where exactly do people look when they grasp an object? An object is usually contacted at two locations, whereas the gaze can only be at one location at the time. We investigated participants' fixation locations when they grasp objects with the contact positions of both index finger and thumb being visible and compared these to fixation locations when they only viewed the objects. Participants grasped with the index finger at the top and the thumb at the bottom of a flat shape. The main difference between grasping and viewing was that after a saccade roughly directed to the object's center of gravity, participants saccaded more upward and more into the direction of a region that was difficult to contact during grasping. A control experiment indicated that it was not the upper part of the shape that attracted fixation, while the results were consistent with an attraction by the index finger. Participants did not try to fixate both contact locations. Fixations were closer to the object's center of gravity in the viewing than in the grasping task. In conclusion, participants adapt their eye movements to the need of the task, such as acquiring information about regions with high required contact precision in grasping, even with small (graspable) objects. We suggest that in grasping, the main function of fixations is to acquire visual feedback of the approaching digits.},
    author = {Brouwer, Anne-Marie and Franz, Volker H. and Gegenfurtner, Karl R.},
    day = {16},
    doi = {10.1167/9.1.18},
    issn = {1534-7362},
    journal = {Journal of Vision},
    keywords = {biology, eye-movements, grasping, motor},
    month = jan,
    number = {1},
    pmid = {19271888},
    posted-at = {2013-07-05 10:24:08},
    priority = {2},
    publisher = {Association for Research in Vision and Ophthalmology},
    title = {Differences in fixations between grasping and viewing objects},
    url = {http://dx.doi.org/10.1167/9.1.18},
    volume = {9},
    year = {2009}
}

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An image is highly salient where

  • there is high contrast,
  • there is high variance,
  • it has distinctive higher-order statistics,
  • there is high local symmetry.

People fixate on different parts of an image depending on the questions they are asked or task they are trying to accomplish.

People look where they point and point where they look.

Reasons why pointing and gazing are so closely connected may be

  • that gaze guides pointing,
  • that gazing and pointing use the same information,
  • or that a common motor command guides both.

Brouwer et al found that their subjects looked more at the contact position of the index finger when they were told to grasp an object than when they were just to look at it.

In the first experiment by Brouwer et al, people fixated different parts of a shape depending on whether the task was just to look at it or grasp it.

The subject's initial saccade, however, was not influenced by the task.