Kentaro Kotani

Alternative Computer Mouse Design and Testing to Reduce Finger Extensor Muscle Activity During Mouse Use

Objective: The purpose of this study was to design and test alternative computer mouse designs that attempted to reduce extensor muscle loading of the index and middle fingers by altering the orientation of the button switch direction and the force of the switch. Background: Computer users of two-button mouse designs exhibit sustained lifted finger behaviors above the buttons, which may contribute to hand and forearm musculoskeletal pain associated with intensive mouse use. Methods: In a repeated-measures laboratory experiment, 20 participants completed point-and-click, steering, and drag tasks with four alternative mouse designs and a reference mouse. Intramuscular and surface electromyography (EMG) measured muscle loading, and movement times recorded by software provided a measure of performance. Results: Changing the direction of the switch from a conventional downward to a forward design reduced (up to 2.5% maximum voluntary contraction [MVC]) sustained muscle activity (10th percentile EMG amplitude distribution) in the finger extensors but increased (up to 0.6% MVC) flexor EMG and increased movement times (up to 31%) compared with the reference mouse (p < .001). Implementing a high switch force design also increased flexor EMG but did not differ in movement times compared with the reference mouse (p < .001). Conclusion: The alternative mouse designs with altered switch direction reduced sustained extensor muscle loading; however, trade-offs with higher flexor muscle loading and lower performance existed. Application: Potential applications of this study include ergonomic and human computer interface design strategies in reducing the exposure to risk factors that may lead to upper extremity musculoskeletal disorders.

Evaluation on a keystroke authentication system by keying force incorporated with temporal characteristics of keystroke dynamics

This paper presents the study to develop and evaluate techniques to authenticate valid users, using the keystroke dynamics of a users PIN number entry on a numerical keypad, with force sensing resistors. Added with two conventional parameter lists of elements, i.e. digraph latency times and key hold times, keying force was chosen as a third element. Two experiments were conducted. The first experiment was to evaluate whether the three types of elements derived from keystrokes have a significant effect for subjects and to examine how trials and session effects generated the variation of the three elements. The second experiment was to demonstrate the system performance by calculating the False Rejection Rate (FRR) and the False Acceptance Rate (FAR) of the system. In the second experiment, a total of 20 keystrokes were recorded from each subject one week after the memorizing session, in order to evaluate the FRR of the system. To evaluate the FAR of the system, the subjects pretended to be impostors, and therefore they repeatedly watched videotaped pass trials made by a valid user as many times as they desired, and tried to imitate the keystroke dynamics of the valid users. The subjects keystrokes were then evaluated on whether they could fool the system. The first experiment, ANOVA revealed that a significant effect of subject was found on each of all three elements. Trial was not significantly affected to digraph latency times and peak force; however, it was significantly affected to key hold times. There was a trend that keystroke dynamics characterized by each element showed reformation of their patterns and reached a steady state over the 10 weeks of experimental sessions. The results of the second experiment showed the average equal error rate to be 2.4%. The results of system performance were compared with those of other studies and concluded that it was difficult to obtain enough information to behave as a perfect impostor by monitoring the videotaped keystrokes.

Effect of horizontal position of the computer keyboard on upper extremity posture and muscular load during computer work.

The distance of the keyboard from the edge of a work surface has been associated with hand and arm pain; however, the variation in postural and muscular effects with the horizontal position have not been explicitly explored in previous studies. It was hypothesized that the wrist approaches more of a neutral posture as the keyboard distance from the edge of table increases. In a laboratory setting, 20 adults completed computer tasks using four workstation configurations: with the keyboard at the edge of the work surface (NEAR), 8 cm from the edge and 15 cm from the edge, the latter condition also with a pad that raised the work surface proximal to the keyboard (FWP). Electrogoniometers and an electromagnetic motion analysis system measured wrist and upper arm postures and surface electromyography measured muscle activity of two forearm and two shoulder muscles. Wrist ulnar deviation decreased by 50% (4°) as the keyboard position moved away from the user. Without a pad, wrist extension increased by 20% (4°) as the keyboard moved away but when the pad was added, wrist extension did not differ from that in the NEAR configuration. Median values of wrist extensor muscle activity decreased by 4% maximum voluntary contraction for the farthest position with a pad (FWP). The upper arm followed suit: flexion increased while abduction and internal rotation decreased as the keyboard was positioned further away from the edge of the table. In order to achieve neutral postures of the upper extremity, the keyboard position in the horizontal plane has an important role and needs to be considered within the context of workstation designs and interventions.

Design of Eye-Typing Interface Using Saccadic Latency of Eye Movement

The objective of this study was to construct and empirically evaluate an improved, online eye-typing interface with respect to its practical usability. The system used the concept of saccadic latency, a silent period of 200 to 250 msec precedes the initiation of a saccade, for identifying the users intentional text entry. Ten individuals participated in the experiment that was conducted on 2 consecutive days, with three blocks of trials conducted on each day. A block included five trials, each of which involved completing the text entry of a short sentence using this eye-typing interface. The proposed interface was evaluated by the users performance based on indices including typing speed and an error index. For defining the error index, the overproduction rates (ORs) were used. The results showed an average OR of 0.032 and average typing speed of 27.1 characters typed per minute. The result revealed that the typing speed changed as an effect of participant, day, and block. The characteristics of the proposed interface with the related characteristics of an eye-typing interface were summarized to discuss a further study for the eye-typing interface.

Changes in posture of the upper extremity through the use of various sizes of tablets and characters

The aim of this study was to analyze the posture of the upper extremities during the use of mobile communication devices. Using various sizes of mobile devices and display characters, we examined subjective muscular loads, viewing distances, and joint angles in the head, neck, shoulder, elbow, and lower back. No postural differences were found between the use of 7-in and 10-in devices, whereas the head and neck were significantly flexed and the elbow angles were decreased during the use of the 13-in device. Character size significantly affected the viewing distance; however, no differences in body angles were found. Participants continually increased their muscular loads during the task by flexing the head and neck, despite their high subjective discomfort levels in the neck and upper arm.

Evaluation for emergency escape during stair climbing in a simulated flood evacuation

The objective of this study was to measure muscle activity during stair-climbing in order to estimate the water depth at which people can evacuate safely from urban underground. A life-size model of a staircase with a water pump that generated water flow from the top of stairs was constructed. In the study, electromyogram data were measured for six muscles on the right lower extremity, namely, the rectus femoris, vastus lateralis, long head of the biceps femoris, medial gastrocnemius, tibialis anterior, and gluteus maximus. From the results, the GA exhibited the highest muscle activity in the latter part of the stance phase, suggesting that the subjects tended to avoid stumbling against the stream of the water during ankle planter flexion. The results obtained from this study would be used for the construction of a guideline for evacuation from urban underground in flood disaster.

Information processing for constructing tactile perception of motion: a MEG study

We clarified whether temporal changes in information processing exist by comparing real and apparent motion conditions when tactile moving perception was given. We used magnetoencephalography (MEG), which has a high temporal resolution, to capture the dynamic changes in brain information processing. As a result, it was revealed that temporal transition through several cortexes was shown in which initial information processing occurred in the somatosensory cortex, followed by MT/V5, and then the activity was transmitted to motor-related areas when tactile moving stimuli were given.

Hands-free data manipulation for visual inspection system by using temporal characteristics of saccades

In some industrial inspection processes, multi-process, handling workers are required for entering the results of visual inspection tests without using their hands, for efficiency or hygiene reasons. We developed a hands-free visual inspection system by using temporal characteristics of saccadic eye movements. The proposed system is free from the Midas touch problem, i.e., the difficulty in developing an eye-typing interface owing to the difficulty in differentiating between intentional blinks and gazes and natural ones. For verifying the system, an experiment was conducted where five subjects performed a visual inspection task. The average defect detection rates were 85.8%, and no Midas-touch-related errors were observed. Results of error analysis showed that redesigning of the system interface would lead to an enhancement of the system performance.

A Study on Fundamental Information Transmission Characteristics of an Air-Jet Driven Tactile Display

There are many people with impaired vision as well as hearing. Tactile displays can be useful to such people for communicating by means of characters and shapes. Many devices for tactile displays such as oscillators and electrocutaneous stimulators have been developed. However oscillators have two drawbacks: physical stress tends to build up in actuators because of long term exposure to oscillations, and they may transmit erroneous information because of unstable contacts between magnetic pins and the skin. Moreover, electrocutaneous stimulators cause discomfort to the user. In this study, we have developed a tactile information presentation technique that uses air jet stimulations and tactile phantom sensations induced by a complex combination of tactile perceptions. The tactile display can transmit information to the skin without physical contact and is free from the restriction of pitch size. In this paper, we have examined its fundamental information transmission characteristics.

Computer task-based evaluation technique for measuring everyday risk-taking behavior

Human risk-taking behavior is a major factor for accidents. Several techniques for quantifying human risk-taking tendency include questionnaire and observation methods. These techniques, however, have been questioned their validity and reliability. Our objective was to propose and evaluate a computer task-based evaluation technique for measuring everyday risk-taking tendency. In this technique, the users perform tracing a certain length of pathway, from start to goal, shown on the display by mouse. The system monitors the trajectory of the mouse cursor and detects the point of decision-making when users change their strategy from steering motion to ballistic motion as the mouse cursor approaches to the goal, yielding the level of risk-taking behavior represented by the Index of Difficulty (ID) at the location of strategy change. The results of experiment showed that IDs were highly correlated with probabilities of risk-taking behaviors obtained from 16 question items.