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HCI

Response to [Characterizing User Performance… ] by Ens et al.

ONE SENTENCE

Ens et al. characterized users’ performance of direct off-screen pointing parameterized with different visual cues and styles of interactions.

MORE SENTENCES

Direct off-screen pointing is the ability to directly point at objects that are outside the viewport. This paper analyze a particular instance: direct off-screen pointing with assisted on-screen visual cues, and pre-defined interaction styles. To characterize users’ performance, they first created a model to predict the moving time. Further, their study showed that pointing time and accuracy are dependent on the type of feedback given to users during the tasks. The study also validated the aforementioned model, and gave implications for design and applications.

KEY POINTS

  • Direct off-screen pointing is the ability to directly point at objects that are outside the viewport;
  • Little attention has been given to direct interaction in the surrounding off-screen  space;
  • Steering law is applicable to tasks where users continually modify their motion path in response to changing stimulus throughout the entire motion;
  • … we can view the Fitts’ law and the steering law as upper and lower bounds, respectively, of an assisted pointing task using the glide interaction;
  • We show that pointing time and accuracy are dependent on the type of feedback given to users during the task;
  • Our results show that:
    • regardless of interaction style, the type of dynamic off-screen target cues dictate pointing performance;
    • the correction of pointing error can take as much as three quarters of the overall selection time, thus improving this phase can lead to significant performance benefits;
    • sophisticated cues can be highly accurate but with up to three times the cost in throughput;
    • our derived model provides a good explanation and prediction for pointing performance;
    • performance changes with target position around the device.

INSPIRATIONS

  1. Get inspired by Fitts’ Law – to consider 1) A (Euclidian distance between the starting position and the center position of the target); and 2) W (the target width);
  2. Employing visual cues might be an important variable;
  3. Think: is it okay to just study a particular direction (e..g, right)?
  4. Might be interesting: coarse-grained vs. fine-grained movements.
  5. Three more readings: Accot et al’s CHI 97. Fitts’ Law paper, Wang et al’s J. Hum.-Comput. Stud.
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About Xiang 'Anthony' Chen

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