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Usability Evaluation of Touchless Mouse Based on Infrared Proximity Sensing

Young Sam Ryu, Do Hyong Koh, Dongseok Ryu, and Dugan Um

Journal of Usability Studies, Volume 7, Issue 1, November 2011, pp. 31 - 39

Article Contents


Methods

The following sections discuss the design, participants, equipment, and task and procedure methods used in this study.

Design

The experiment was within-subject, in which the dependent variables were the completion time, throughput, and number of errors. The independent variable was the type of input method (conventional mouse vs. T-less mouse).

Participants

A total of 18 participants were recruited to participate in the experiment. The average age of participants was 25 years old, with a standard deviation of 4.8 years. There were 4 female and 14 male participants. Among the 18 participants, two participants claimed they were left-handed. However, both of them indicated they use their right hand to control a computer mouse. Thus, every participant used their right hand to control the T-less mouse in this study. Fifteen participants indicated they have used a track-ball mouse in addition to a conventional mouse. The average rating of the level of comfort using a conventional mouse was 6.5 (1=lowest, 7=highest) with 0.70 standard deviation. Self-rated proficiency in using a conventional mouse was 6.27 (1=lowest, 7=highest) in average with 0.89 standard deviation.

Equipment

A participant was seated in front of a computer with two extended monitors. One screen was used to display practice and test information; the other screen was used to display the T-less mouse interface. Both monitors were 19 inch flat panel screens with resolution of 1600x1200. The experiment was conducted with a T-less mouse interface that recognizes the finger motion and generates commands to control the computer’s cursor.  The distance information detected by the IPA subsystem of the T-less mouse is fully utilized to distinguish the finger gestures. In addition, in order to reduce unnecessary motion and fatigue, the participants were instructed to put their hands on the desk between trials.

Task and Procedure

The procedure consisted of four parts: pre-test survey, practice session, test sessions, and post-test survey. Each participant completed a pre-test survey first. Then, they completed the practice and test sessions. After the test session, the participants were asked to complete a post-test survey.

The pre-test survey collected demographic data such as age and gender. In addition, we asked whether participants are right-handed or left-handed, whether they have experience using a trackball or mouse, and which hand is used for operating a conventional mouse. The participant’s proficiency of using a mouse and contentment of using a mouse were also coded using a 7-point Likert scale.

The practice session was designed to make participants more comfortable with the T-less mouse. In the practice session, a facilitator explained how the T-less mouse works and demonstrated how to move the cursor to hit a target. After the demonstration, participants familiarized themselves with the use of the T-less mouse for five minutes. In order to preclude any learning effects, the facilitator did not provide any information about the actual tasks contained in subsequent sections of the experiment. Instead, a practice task was presented to participants to simulate selection of targets. The dummy task screen contained four targets and one home target. The facilitator verbally asked participants to move the cursor to multiple targets, including the home target. Figure 2 shows a screen shot of the practice task.

Figure 2

Figure 2. The practice session screen

In the test session, multi-directional Fitts’ Law discrete tasks were presented to participants. The design of the multi-directional Fitts’ Law tasks was based on ISO 9241-9 (2000) and adapted from Zhang and MacKenzie (2007). Participants had to complete a total of three sets of tasks, one with a conventional mouse and two with the T-less mouse. The multi-directional Fitts’ Law discrete task measured the performance of a target selection scheme via throughput. The goal of the task was to select the sequence of targets presented at various eccentricities from the center of the screen that initialized each subsequent selection from the screen's center.

Figure 3 illustrates an example of the target selection task. In our experiment, Fitts’ Law discrete task test was conducted with a fixed target distance (500 pixels). Each trial started with an initial target appearing at the center of the screen. As soon as the initial target was hit, a target appeared on the screen at a new location and a timer for the selection completion time was initiated. The participant’s goal was to select this target as quickly as possible. The target was available until it was hit successfully, i.e., sometimes participants had to make multiple attempts before the target was hit successfully. Once participants hit the target successfully, the initial target appeared again. This sequence was repeated until participants selected 16 targets for the same target distance. Once the coordinates of the first selection point by each selection scheme were recorded, the trial ended and the duration for the target selection completion was recorded. In order to avoid learning effects, the order of the selection schemes was counter-balanced. Due to the technical difficulty of the selection gesture of T-less mouse (i.e., mouse click), targets were selected (clicked) automatically following a cursor dwell-time of two seconds on each target. The dwell-time of two seconds was an arbitrary choice to avoid any involuntary clicks that may result in over-estimating the number of error clicks.

Figure 3

Figure 3. Multi-directional Fitts’ Law test: A) Home target appears in the center. B) A cursor is moving toward a target. C) The cursor is now on the target and target is selected. D) Home target appears again.

At the end of the task trials, participants were asked to complete a survey containing a Device Assessment Questionnaire suggested by ISO 9241-9 guidelines, with some questions modified to be more related to the T-less mouse. All questions were rated on a 7-point Likert scale from strongly agree to strongly disagree. The following were the questions asked on the questionnaire:

  1. The mental effort required for operation was (low=1 to high=7)
  2. Wrist fatigue was (low to high)
  3. Shoulder fatigue was (low to high)
  4. Arm fatigue was (low to high)
  5. The physical effort required for operation was (low to high)
  6. Smoothness during operation was (rough to smooth)
  7. Accurate pointing was(difficult to easy)
  8. Operation speed was (slow to fast)
  9. Ease of target selection was (difficult to easy)
  10. Which will you prefer the T-less mouse or a mouse? (mouse=1 to T-less mouse=7)
  11. General comfort was (uncomfortable to comfortable)
  12. Overall, the interaction was (difficult to easy)
  13. The T-less mouse was designed to replace conventional mouse in special work settings such as outdoor environment or when users wear gloves. In such occasions when conventional mouse is not ideal to use, do you think T-less mouse can be good enough to replace conventional mouse? (No to Yes)

Also, there were two open-ended questions asking for comments related to problems of using the T-less mouse and any suggestions to improve it.

 

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