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TIPS ABOUT THESE VISUALIZATIONS and a few facts for those who have not yet had time read the cited papers: a) The multipointed red star shows the position of the Sparker (a pair of electrodes) worn on top of the head. It is used to measure head translations. Movements of the red star show how the head moves in space. b) Black balls are eyeballs ("e" toggles them on and off as does the button on bottom). When the eyeballs are toggled-off, the lines-of-sight can be seen to start at the subject's right eye and left eye "sighting centers", which are measured psychophysically. c) Black lines are the lines-of-sight of each eye. The blue line is cyclopean gaze ("c" toggles it on and off in addition to the button at the bottom). Cyclopean gaze starts at the midpoint of the line connecting the sighting centers. The other end of cyclopean gaze is defined by a unique point, the point nearest to both lines-of-sight (see reference 1, above). d) Frames Skipped and % Actual time: The maximum frame rate is 488 Hz, so if you pick the 1-button, you will step through the data in steps separated by only 2.04 msec. N.B., even on a red hot platform it takes quite a while to get through a 9 second eye movement recording trial. The Frames-skipped default is set to skip 12 frames. Do not change the number of frames skipped while a trial is running. e) Double-clicking on |-+ directory shows or hides the directory's contents. For Tap-Look Visualizations, you select your condition, Look or Tap, and subject, Han Collewijn (HC), Casper Erkelens (CE), Zygmunt Pizlo (ZP), Robert Steinman (RS), the target configuration and the numbered trial in the leftmost window. Now you can Run the trial and watch the subject actually performing the required task. After the trial is over (flashing lights, if any, stop flashing and the screen resets) a %Actual time will be shown below the Frames Skipped setup on bottom of the window. The speed the trial runs depends on your machine so don't be surprised if it is as high as 200 - 400% or as low as 25 - 100%, e.g., My 550MHz i686 SuSe Linux box comes in at about 40% and my 1.7GHz Pentium 4 running Windows 2000 comes in at about 355%. If you want to watch performance in realtime (100%), skip fewer or more frames, using the reset buttons or slider, to slow it down or to speed it up appropriately. Go to skipping only 1 or two frames if you want to watch the details of a large disjunctive saccade and events following its completion. This is fun, albeit time consuming. You can stop a trial while it is running by pressing an
arrow key or by using the stop button. Once stopped, you can
step through the trial forward (=>) or backwards (<=)
by pressing one of these keys, repeatedly. This feature is
particularly useful when you want to examine individual events
such as a large saccade shifting gaze through 100 or more
degrees. You can watch gaze shift in 2.04 msec steps. In most conditions, the experimenter specified the order in which the targets were to be only looked at or tapped. The order specified did not change in this series of experiments. Subjects were required to Look or Tap in the following order: gold, green, red, flashing gold, flashing green and flashing red when 6-target configurations were used. The order was the same with 2- and 4-target sets, i.e., gold and green, or gold, green, red and flashing gold, respectively. Data were also collected when subjects could select their own order (subj-or.der). g) You can change your views from Behind to Left to Front and zoom in or out (Magnify/Minify) within a trial. You can change your point of view as well. h) BE SURE TO CLICK ON THE APPLY BUTTON TO IMPLEMENT ANY CHANGES MADE TO THE BOTTOM SECTION! i)
N.B.,
these visualizations are not simulations, or posthoc fits of
eye movement data to the environment. The
gaze and head movements shown were calculated from independent
measures of sighting centers, head & eye rotations and
translations, and the positions of the nearby objects in a
calibrated workspace. |
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