Evaluation of Mouse, Rate-Controlled Isometric Joystick, Step Keys, and Text Keys for Text Selection on a CRT

Abstract

Four devices are evaluated with respect to how rapidily they can be used to select text on a CRT display. The mouse is found to be fastest on all counts and also to have the lowest error rates. It is shown that variations in positioning time with the mouse and joystick are accounted for by Fitts's Law. In the case of the mouse, the measured Fitts's Law slope constant is close to that found in other eye-hand tasks leading to the conclusion that positioning time with this device is almost the minimal achievable. Positioning time for the key devices is shown to be proportional to the number of keystrokes which must be typed.

Enhancing input device evaluation

“…The cited paper by Card et al [2] already incorporated a longitudinal design to assess learning effects of different pointing devices in 1978. In 1999 MacKenzie & Figure 1: Using the laser-pointer in a multi-directional tapping task in front of large high -resolution display Zhang [8], while comparing a optimized keyboard layout with the traditional QWERTY standard, stated that "users who bring desktop computing experience to mobile computing may fare poorly on a non-QWERTY layout -at least initially.…”

“…This is especially the case with the evaluation of pointing devices which relies on a highly standardized procedure in terms of tasks (uni-or multi-directional tapping tasks) and experimental designs. This goes back to Card et al 1978 who were the first to show that Fitts' Law could be used to predict pointing performance [2]. In 1954 Fitts discovered a linear relation between movement time (time to point onto a target) and the difficulty ofthe task (depending on the target size and the amplitude between the starting position and the target) [3].…”

Action graphs and user performance analysis

“…The Fitts Law estimates aimed movement times, based on distance and target size. Since the seminal work of Card, English, and Burr (1978), the Fitts Law has been widely used in HCI: for example, given the position and size of buttons it provides an estimate of the lower bound on the time it would take a user to move their finger from one to the other, thus leading to design insights.…”

Insight into Goal-Directed Movements: Beyond Fitts’ Law

“…total path length divided by total time 1 Counter-productive submovements: Number of times the coincident error is negative with a magnitude larger than the submovement's starting distance 1 [9] Deceleration time: Time interval during which the pointer was decelerating 1 [18] Distance to peak speed: Distance traveled from movement onset to the moment peak speed is reached 2 Error magnitude: Distance from the position of the target miss (button click) to the target edge 3 Final positioning time: Interval from target entry until the end of the trial 3 [2] Goal distance correction phase: Distance to the target at the start of the correction phase 3 High curvature occurrence: Number of times the angle between 3 sample points is less than 80 deg 1 [6] Length offset: Difference between the length of the ballistic phase and 'distance to target' at the beginning of the ballistic phase 2 [8] Max percent overshoot: largest percent deviation from the target once the pointer passes the target 2 [3] Movement direction change: Number of times the tangent to the path gets parallel to the task axis 1 [14] Movement error: Mean of absolute distances of the path from the task axis 1 [14] Movement offset: Overall mean distances of the path from the task axis 1 [14] Movement time: time interval from movement onset to movement offset 4 [16] Movement variability: Extent to which the path lies in a straight line parallel to the task axis 1 [14] Orthogonal direction change: Number of times the tangent to the path becomes perpendicular to the task axis 1 [14] Overshoot: the frequency and duration (time interval from the moment the pointer passes the target edge to movement offset) of overshoots 2 [9,3] Path length: Length of the path in mm 1 Path length efficiency: Ratio between the shortest path and the traveled path 1 [11] Pauses: Number of pauses (>0ms; >100ms; >250ms) [11] and mean duration of the pauses 1 [9] Peak acceleration: Maximum acceleration reached during the overall movement 2 [7] Peak deceleration: Maximum deceleration reached during the overall movement 2 [7] Peak speed: Maximum speed reached during the movement 2 [11] Peak time: time at which maximum overshoot is reached 2 [3] Perpendicular error: Distance between the endpoint of the ballistic phase and the task axis, measured in the direction normal to the task axis 2 …”

“…Several studies have compared input devices or interaction techniques by observing characteristics of movement paths during the execution of basic tasks such as pointing, selecting or steering [4,10,15,14,9,8]. From these comparative studies two different approaches towards movement analysis can be discerned.…”