Michael Bohan

WHEN DOES IMAGERY PRACTICE ENHANCE PERFORMANCE ON A MOTOR TASK

Imagery practice of motor tasks has been recommended for a wide range of activities as from flight training to basketball. A key question, both from a practical and a theoretical standpoint, is when during the learning process does imagery practice confer the most benefit? However, the literature does not provide clear guidance, in part because of methodological limitations. A 3 × 2 (physical practice X pretest-posttest) split-plot design was employed to investigate the effects of imagery practice on the acquisition of a discrete target at three different stages of learning. Analysis indicated that imagery practice was most beneficial in the early stages of learning and showed an inverse relationship between experience and efficacy of imagery practice. Results are discussed in terms of current theories of imagery practice and suggestions are made regarding when such practice might be best applied during skill development.

The Effects of Selection Technique on Target Acquisition Movements Made with a Mouse

Research has shown that a significant amount of the time needed to acquire on-screen targets with a mouse can be spent in the selection phase. Thus we are exploring alternative modes of target selection that may reduce this time. In the present experiment, participants acquired targets of varying distance and size. Two methods for target selection were compared: (1) the standard button-select technique, (2) and a mouse-over technique, in which targets were designated when the cursor and target were superpositioned for 350 ms. Results showed that target-acquisition times were significantly shorter for the mouse-over technique, particularly at the smallest target size. There was also evidence that the effects were localized in the selection phase. Overall, the results suggest that the mouse-over technique can be an effective alternative to selelcting targets via button press. Potential applications and limitations of this procedure are discussed.

Gain and target size effects on cursor-positioning time with a mouse

Movement time to align a cursor with targets on a computer screen a mouse was examined across settings of gain and target size. Empirical evidence was sought in light of previous suggestions that performance declines observed at higher gains can be explained by decreased effective cursor resolution, not gain per se. We tested this hypothesis by holding the effective cursor resolution constant while systematically varying gain and target size. Analysis of movement times showed a significant gain effect as a function of target size. Specifically, movement time increased with gain at the smallest target size (i.e. 1.5 mm) but decreased with gain at the largest target size (i.e. 12 mm). These results do not support the no-effect of gain hypothesis and suggest that target size is an important factor in determining the effects of gain on mouse movement performance.

To click or not to click: a comparison of two target-selection methods for HCI

This paper reports a preliminary investigation of diffemnt methods for target selection on a computer screen using a mouse. Specifically, an experiment compared the standard point-and-click method to a mouse-over method, whereby the target was automatically selected atIer the cursor and target were superpositioned for 200 ms. Results indicated that the mouse-over method resulted in a significant reduction in target-acquisition time across a range of target widths. The implication of these findings to task optimization are then considered.

Comparing Computer Input Devices Using Kinematic Variables

Throughput (TP) is a global measure of input device efficiency but provides little information about users movement behavior when interacting with a device. Psychomotor models of movement provide a framework from which to develop new “during” movement variables that can be used to explain why efficiency differences occur. Data from a previous study examining the usability of a mouse, trackball and RollerMouse™ was re-examined using TP and the kinematic variables peak velocity of the primary movement (PV) and proportion of total distance traveled in primary phase (%PMD). Partial correlation analysis found %PMD and PV to be significantly related to TP and negatively related with each other, suggesting a “speed/accuracy” tradeoff. Further analysis confirmed the variables were useful in discriminating between devices and found that the most efficient device was less constrained by the “speed/accuracy” tradeoff. It was concluded that kinematic variables offer a useful way of understanding efficiency differences between devices.

An Investigation of Dwell Time in Cursor Positioning Movements

Recently, researchers have emphasized the need to examine the separate phases of movements using electromechanical pointing devices in human-computer interaction. It has been shown that up to 50% of total time to select a target is spent in the dwell phase (interval of time between the termination of overt movement and target designation via button press, etc.). The present study tested the visual feedback processing hypothesis as an explanation for the functional significance of dwell time in cursor-positioning movements. Results indicate that the duration of dwell time could not be fully accounted for by changes in visual processing demands. Instead, it appears that a critical determinant of dwell time duration is the implementation of different cognitive strategies regarding the stage in the movement at which certain parameters (e.g. target width and distance) are accounted for.

A Comparison of Cursor-Control Performance of the Rollermouse Station™ and the Standard Mouse

This study compared first-time usage and performance of the RollerMouse Station™ to the standard mouse. Participants completed serial-clicking and serial-dragging tasks using a variety of angles, distances, and sizes on both input devices. Movement time, homing time, and error rate per condition were examined as dependent variables. Results revealed faster point-and-click and click-and-drag performance for the standard mouse but no difference in error rate across the two devices. In addition, the RollerMouse was significantly faster for homing time. Although the standard mouse was faster in target acquisition, the increase in performance from the homing time for the RollerMouse resulted in only a slight advantage for the mouse in total movement time. These results are promising for the RollerMouse as an alternative input device to the mouse. Further studies investigating the effects of practice and hand configuration are discussed.

Examining First-Time Usage of the CombiMouse™

The CombiMouse™ is a new input device for personal computers that combines the functionality of a keyboard and a mouse into one device. The CombiMouse™ consists of two units, much like a split-keyboard, in which the left hand unit (LHU) is a stationary device with keys that are typically used by the left hand, while the right hand unit (RHU) contains keys typically used by the right hand, but is mobile and serves as a mouse. Preliminary results of first-time usage indicate the device to be very promising. Performance was shown to be just as efficient as the traditional mouse and significantly more efficient than the track ball. Typing performance was not as fast as the traditional keyboard; however, the participants showed improvement with more usage of the device.

Evaluation of the Wristcorder™: A hand-forearm motion analyzer

For effective control and assessment of harmful hand-forearm motion at work, a valid goniometric system that produces reliable and accurate measurements is essential. The present study evaluated the WristCorderTM, a portable motion analyzer for flexion/extension (F/E), ulnar/radial deviation (U/R), and pronation/supination (P/S) of the hand-forearm, in terms of linearity, sensitivity, and reliability using the Triaxial Hand-Forearm Fixture. Eight participants having no history of musculoskeletal disorders were recruited for the evaluation. The motion analyzer produced sensor values linearly related to angular movements of the limb; sensitivity was less than 1° for F/E and U/R and between 2.5° and 3.5° for P/S; standard deviation due to measurement error was about 1° for F/E and U/R and about 2.4° for P/S; and standard error of measurement was less than 1° for F/E and U/R and 2.3° for P/S. The motion analyzer may be used as an effective tool to analyze unidimensional movements of the hand-forearm in industry. Continued study is needed to generalize the evaluation results in three-dimensional motion analysis.