Building a Low-Cost Wireless Biofeedback Solution: Applying Design Science Research Methodology.

In recent years, affective computing has emerged as a promising approach to studying user experience, replacing subjective methods that rely on participants' self-evaluation. Affective computing uses biometrics to recognize people's emotional states as they interact with a product. However, the cost of medical-grade biofeedback systems is prohibitive for researchers with limited budgets. An alternative solution is to use consumer-grade devices, which are more affordable. However, these devices require proprietary software to collect data, complicating data processing, synchronization, and integration. Additionally, researchers need multiple computers to control the biofeedback system, increasing equipment costs and complexity. To address these challenges, we developed a low-cost biofeedback platform using inexpensive hardware and open-source libraries. Our software can serve as a system development kit for future studies. We conducted a simple experiment with one participant to validate the platform's effectiveness, using one baseline and two tasks that elicited distinct responses. Our low-cost biofeedback platform provides a reference architecture for researchers with limited budgets who wish to incorporate biometrics into their studies. This platform can be used to develop affective computing models in various domains, including ergonomics, human factors engineering, user experience, human behavioral studies, and human-robot interaction.

Prediction of the use of mobile device interfaces in the progressive aging process with the model of Fitts' law.

PURPOSE: As the population ages, so do the potential users of technology, and older adults' behaviors when using mobile device interfaces are becoming increasingly important. A representative model for detecting older adults' behaviors and performance on the use of mobile device interfaces is needed to provide individualized designs. This research aimed to investigate the applicability of the broadly used model of Fitts' law to detect the progressive changes in the use of mobile device interfaces in older adults. The effect of experience with using technology on performance on a Fitts task was also examined. METHOD: A sample of 135 older adults was recruited to test the application of Fitts' model to the use of technology by older adult users. Each participant was asked to finish tasks at 9 levels of difficulty, from easy to difficult, in a multidirectional tapping task. Analysis of variance was employed to examine the effect of age on performance on the Fitts task, movement time, and the standard deviation of movement time. Stepwise regression was used to investigate how well age and technology use could predict performance on the Fitts task. RESULT: Performance on the Fitts task was sensitive to the gradual changes in abilities with aging. Rather than the amount of experience in using technology, age was the stronger predictor of older adults' performance on the Fitts task. Additionally, compared with the younger groups, the users above 80 years old demonstrated significantly higher behavioral variation during the use of mobile device interfaces. CONCLUSION: This research confirmed that Fitts' law is applicable to the evaluation of the effects of aging on the use of mobile device interfaces. Adults above the age of 80 years should be a major focus for special individualized interface design. This finding can inform future designers and researchers in the development of individualized interface designs for older adult users to enhance their user experiences of mobile device technology. RELEVANCE TO INDUSTRY: Future designers and researchers can apply the finding on Fitts' law in this research to develop user-friendly interface designs for mobile technology for older adults and thereby improve their user experiences to enhance their independence and quality of life through the use of technology.

Impact of parallax and interpupillary distance on size judgment performances of virtual objects in stereoscopic displays.

Effective interactions in both real and stereoscopic environments require accurate perceptions of size and position. This study investigated the effects of parallax and interpupillary distance (IPD) on size perception of virtual objects in widescreen stereoscopic environments. Twelve participants viewed virtual spherical targets displayed at seven different depth positions, based on seven parallax levels. A perceptual matching task using five circular plates of different sizes was used to report the size judgment. The results indicated that the virtual objects were perceived as larger and smaller than the corresponding theoretical sizes, respectively, in negative and positive parallaxes. Similarly, the estimates from participants with small IPDs were greater than the predicted estimates. The findings of this study are used to explain human factor issues such as the phenomenon of inaccurate depth judgments in virtual environments, where compression is widely reported, especially at farther egocentric distances. Furthermore, a multiple regression model was developed to describe how the size was affected by parallax and IPD. Practitioner Summary: The study investigates the effects of parallax and interpupillary distance on size perception of virtual targets in a stereoscopic environment. Virtual objects were perceived as larger in negative and smaller in positive parallax. Also, size estimates were greater than the theoretical sizes for participants with smaller IPD. A multiple-regression model explains the impact of parallax and measured IPD. Abbreviations IPD interpupillary distance VR virtual eality HMD head mounted-displays 2AFC two-alternative forced choice IOD interocular distance PD pupillary distance ANOVA analysis of variance.

Training Performance of Laparoscopic Surgery in Two- and Three-Dimensional Displays.

INTRODUCTION: This research investigated differences in the effects of a state-of-art stereoscopic 3-dimensional (3D) display and a traditional 2-dimensional (2D) display in simulated laparoscopic surgery over a longer duration than in previous publications and studied the learning effects of the 2 display systems on novices. METHODS: A randomized experiment with 2 factors, image dimensions and image sequence, was conducted to investigate differences in the mean movement time, the mean error frequency, NASA-TLX cognitive workload, and visual fatigue in pegboard and circle-tracing tasks. RESULTS: The stereoscopic 3D display had advantages in mean movement time ( P < .001 and P = .002) and mean error frequency ( P = .010 and P = .008) in both the tasks. There were no significant differences in the objective visual fatigue ( P = .729 and P = .422) and in the NASA-TLX ( P = .605 and P = .937) cognitive workload between the 3D and the 2D displays on both the tasks. For the learning effect, participants who used the stereoscopic 3D display first had shorter mean movement time in the 2D display environment on both the pegboard ( P = .011) and the circle-tracing ( P = .017) tasks. CONCLUSIONS: The results of this research suggest that a stereoscopic system would not result in higher objective visual fatigue and cognitive workload than a 2D system, and it might reduce the performance time and increase the precision of surgical operations. In addition, learning efficiency of the stereoscopic system on the novices in this study demonstrated its value for training and education in laparoscopic surgery.

The postural and control-display gain effects of distal pointing on upper extremity fatigue.

Pointing at displays from a distance is becoming common in both work and domestic environments. Ray-casting interaction is easy for novices to learn and understand, but this technique can cause physiological fatigue. To address this issue, the present study aims to investigate the issue of fatigue caused by joint-based pointing methods and Control-Display gains (CD gains) via Fitts' task. Ten healthy subjects participated in the experiment and performed multi-directional tapping tests with three joint-based pointing methods and three CD gains. The experimental results indicated that the joint-based pointing methods indeed affected the physiological and subjective fatigue of the upper limb muscles and measured body parts during distal pointing tasks. The wrist-based pointing method, which can induce substantially lower physiological and subjective fatigue, appears to be superior to the other two methods. There were no significant main effects of CD gains on either physiological fatigue or subjective Borg's CR-10 rating. PRACTITIONER SUMMARY: The present study investigates the issue of fatigue caused by joint-based pointing methods and CD gains via Fitts' task. The pointing methods affected the physiological and subjective fatigue of the upper-limb muscles. There were no significant main effects of CD gains on either physiological fatigue or subjective Borg's CR-10 rating.

Time Pressure Affects the Risk Preference and Outcome Evaluation.

It is ubiquitous that food delivery riders do not have unlimited periods of time for deliberation to make decisions. Time pressure plays a significant role in decision-making processes. This study investigated how time pressure affected risk preference and outcome evaluation through behavioral and electrophysiological responses during decision-making. Participants finished a simple gambling task under three different time constraint conditions (high/medium/low). Behavioral and event-related potentials (ERPs) data were recorded during the experiment. The results showed that the decision time of people was shorter under high time pressure than under medium and low time pressures. People tend to make more risky choices when under high time pressure. The feedback-related negativity (FRN) amplitude was smaller in the high time pressure than in medium and low time pressure conditions. These findings provided evidence that time pressure has an impact on the risk decision-making process.

Visual assessment of camouflaged targets with different background similarities.

The study investigated the effectiveness of different camouflage designs using a computational image quality index. Camouflaged human targets were presented on a natural landscape and the targets were designed to be similar to the landscape background with different levels of background similarity as estimated by the image index. The targets were presented in front of the observer (central 0 degrees) or at different angles in the left (-7 degrees, -14 degrees, -21 degrees) or right (+7 degrees, +14 degrees, +21 degrees) visual fields. The observer had to detect the target using peripheral vision if the target appeared in the left and right visual fields. The camouflage effectiveness was assessed by detection hit rates, detection times, and subjective ratings on detection confidence and task difficulty. The study showed that the psychophysical measures correlated well with the image similarity index, suggesting a potentially more efficient camouflage effectiveness assessment tool if the relationship between the psychophysical results and the index can be quantified in the future.

Effects of virtual target size, position, and parallax on vergence-accommodation conflict as estimated by actual gaze.

Due to the increased utilization of stereoscopic displays, the scope of the vergence-accommodation conflict has been studied extensively to reveal how the human visual system operates. The purpose of this work was to study the phenomenon of vergence-accommodation conflict by comparing the theoretical eye vergence angle (vergence response) and gaze-based eye vergence angle (vergence stimulus) based on eye tracker gaze data. The results indicated that the gaze-based eye vergence angle was largest at the greatest parallax. The result also revealed that the eye vergence angle accuracy was significantly highest at the nearest parallax. Generally, accuracy improves when virtual objects are put in the middle and close to participants' positions. Moreover, the signed error decreases significantly when the virtual object is in the middle. Based on the results of this study, we can gain a greater understanding of the vergence-accommodation conflict in the stereoscopic environment.

Effects of mental fatigue on risk preference and feedback processing in risk decision-making.

Mental fatigue is a common phenomenon in modern people, especially after a long period of mental work. Individuals frequently have to make critical decisions when in a mentally fatigued state. As an important and complex cognitive function, risk decision-making might be influenced by mental fatigue, which is consequent with increased distraction and poor information processing. However, how mental fatigue shapes individuals' decision-making remains relatively unclear. The purpose of this study was to examine the effect of mental fatigue on risk decision-making performance and risk-preference in a simple gambling task, using both behavioral methods and event-related potential techniques. Forty young adults were divided into a mental fatigue group and a no-fatigue group and participated in the experiments. Results showed that individuals with mental fatigue tended to be more risk-averse than those without fatigue when facing risk options. The P300 amplitudes were smaller and FRN amplitudes were larger in the mental fatigue group than in the no-fatigue group. These findings provide insight into a relationship between mental fatigue and risk decision-making, from the perspective of the neurological mechanism.

The performance of computer input devices in a vibration environment.

This study investigates the performance of a touch screen, mouse and trackball in a motion environment. A Stewart motion platform was used to generate a six-degree-of-freedom motion environment. Participants were placed in an environment where vehicle vibration was simulated. Tasks were used according to Fitts' Law to obtain the movement time, error rate, index of performance and throughput of each input device. The results showed that during static conditions, the touch screen gave the best results. However, in the vibration environment, the mouse gave the best results. The trackball is the worst of the three. The error rate and end-point variation tends to increase for the touch screen in the vibration environment. STATEMENT OF RELEVANCE: This study investigates the performance of a pointing device in a vibration environment. The results showed that during static conditions, the touch screen gave the best results. However, in the vibration environment, the mouse gave the best results. The track ball is the worst of the three. This research achievement can help human-computer interaction design in various dynamic environments such as in sea and land vehicles.

The development of a mobile user interface ability evaluation system for the elderly.

This research aimed to develop a comprehensive evaluation of the mobile user interface abilities of the elderly so that technology can be designed to meet individualized needs. A total of 135 older adults were evaluated with the developed system, the Elderly Mobile User Interface Ability Evaluation System (EMUIAES). The prediction of age and the use of technology on elderly mobile interface usage were investigated based on the findings of the evaluation. The relationship between performance on Fitts' task and elderly mobile user interface ability (EMUIA) was also examined. The findings showed a strong effect of age on the elderly's use of mobile user interfaces. Previous experience with personal and tablet computers also contributed to the use of mobile user interfaces. In addition, this research demonstrated the application of Fitts' law to describe the elderly mobile user interface behaviors, particularly for tasks involving fast tapping and pointing. The EMUIAES can provide future researchers and designers a comprehensive tool to describe the elderly's diverse behaviors and changes in their ability to use mobile interfaces. Individualized interface designs for elderly users can be developed based on these findings to improve the elderly users' experiences of using technology.

Human signal-detection performance in multiscreen monitoring tasks.

Human monitoring performance was compared for different screens within a single display. Participants' performance with random signals and different numbers of split screens was tested for a period of time. The performance measures were hit rate, false alarm rate, and response time. Results indicated that the response time and false alarm rate significantly increased with the number of split screens. Results also showed that signal frequency significantly influenced the false alarm rate. The location of the 9-screen display was analyzed on hit rate and false alarm rate. More attention was paid to the center screen as indicated by both the higher hit rate and false alarm rate. Findings suggest that designers of monitoring systems should take into consideration the trade-off between the number of multiple split screens and the limited human capability for monitoring performance. Furthermore, it is suggested that high risk and critical information should be placed in the center region to be detected effectively.

The accuracy of the frontal extent in stereoscopic environments: A comparison of direct selection and virtual cursor techniques.

This experiment investigated the accuracy of distance judgment and perception of the frontal extent in a stereoscopic environment. Eight virtual targets were projected in a circular arrangement with two center-to-center target distances (18 cm and 36 cm) and three target sizes (0.6 cm, 1.5 cm, and 3.7 cm). Fourteen participants judged the positions of virtual targets presented at a distance of 90 cm from them by employing two different interaction techniques: the direct selection technique and the virtual cursor technique. The results showed overall higher accuracy with the virtual cursor technique than with the direct selection technique. It was also found that the target size significantly affected the frontal extent accuracy. In addition, significant interactions between technique and center-to-center target distance were observed. The direct selection technique was more accurate at the 18 cm center-to-center target distance along the horizontal (x) and vertical (y) axes, while the virtual cursor technique was more accurate for the 36 cm center-to-center target distance along the y axis. During the direct selection, estimations tended to converge to the center of the virtual space; however, this convergence was not observed in the virtual cursor condition. The accuracy of pointing estimations suffered on the left side of participants. These findings could provide direction for virtual reality developers in selecting proper interaction techniques and appropriately positioning virtual targets in stereoscopic environments.

Effects of translational and rotational motions and display polarity on visual performance.

This study investigated effects of both translational and rotational motion and display polarity on a visual identification task. Three different motion types--heave, roll, and pitch--were compared with the static (no motion) condition. The visual task was presented on two display polarities, black-on-white and white-on-black. The experiment was a 4 (motion conditions) x 2 (display polarities) within-subjects design with eight subjects (six men and two women; M age = 25.6 yr., SD = 3.2). The dependent variables used to assess the performance on the visual task were accuracy and reaction time. Motion environments, especially the roll condition, had statistically significant effects on the decrement of accuracy and reaction time. The display polarity was significant only in the static condition.

Kinematic analysis of direct pointing in projection-based stereoscopic environments.

This work investigated the effects of visual information, parallax, and target positions on movement performances in projection-based stereoscopic displays (PSDs). Fifteen (26.5 ±â€¯3.83 years) self-declared right-handed individuals, with normal or corrected to normal visual acuity, completed pointing tasks in stereoscopic and real environments (RE). Three-dimensional spatial data, recorded by a motion system composed of six infrared cameras, was used to compute kinematics of reaching a real/virtual object at a combination of three parallax and nine frontal planar positions. The results indicated that movement in the PSD was slower and needed longer confirmation time than that in the RE. This might be because of the difficulty and misperception of distance associated with PSD. The motions were initiated faster but took longer to complete in vision-based conditions. The overall kinematic parameters were better as targets were presented closer to participants and around the center of displays. However, during pointing at a target that was continuously visible or presented briefly and disappeared, participants applied similar movement strategies to approach the visual objects. The comparable kinematics and movement behaviors in stereoscopic displays encourage the use of direct pointing that would enhance reaching and grasping tasks - which are important in applications such as rehabilitation, surgical training, and other programs that employ upper limbs. In addition, the more natural interaction by direct pointing minimizes the effort of learning new skills to use other devices.

The effect of parallax on eye fixation parameter in projection-based stereoscopic displays.

The promising technology of stereoscopic displays is interesting to explore because 3D virtual applications are widely known. Thus, this study investigated the effect of parallax on eye fixation in stereoscopic displays. The experiment was conducted in three different levels of parallax, in which virtual balls were projected at the screen, at 20 cm and 50 cm in front the screen. The two important findings of this study are that parallax has significant effects on fixation duration, time to first fixation, number of fixations, and accuracy. The participant had more accurate fixations, fewer fixations, shorter fixation durations, and shorter times to first fixation when the virtual ball was projected at the screen than when it was projected at the other two levels of parallax.

Eye Movement Parameters for Performance Evaluation in Projection-based Stereoscopic Display.

The current study applied Structural Equation Modeling (SEM) to analyze the rela-tionship among index of difficulty (ID) and parallax on eye gaze movement time (EMT), fixation duration (FD), time to first fixation (TFF), number of fixation (NF), and eye gaze accuracy (AC) simultaneously. EMT, FD, TFF, NF, and AC were measured in the projec-tion-based stereoscopic display by utilizing Tobii eye tracker system. Ten participants were recruited to perform multi-directional tapping task using within-subject design with three different levels of parallax and six different levels of ID. SEM proved that ID had significant direct effects on EMT, NF, and FD also a significant indirect effect on NF. However, ID was found not a strong predictor for AC. SEM also proved that parallax had significant direct effects on EMT, NF, FD, TFF, and AC. Apart from the direct effect, parallax also had significant indirect effects on NF and AC. Regarding the interrelation-ship among dependent variables, there were significant indirect effects of FD and TFF on AC. Our results concluded that higher AC was achieved by lowering parallax (at the screen), longer EMT, higher NF, longer FD, and longer TFF. Practitioner Summary: The SEM could provide valuable theoretical foundations of the interrelationship among eye movement parameters for VR researchers and human-virtual-reality interface developers especially for predicting eye gaze accuracy.

Effect of vibration on visual display terminal work performance.

Today electronic visual displays have dramatic use in daily life. Reading these visual displays is subject to their vibration. Using a software-simulation of a vibrated environment, the study investigated the effect of vibration on visual performance and fatigue for several numerical display design characteristics including the font size and the number of digits displayed. Both the frequency and magnitude of vibration had significant effects on the reaction time, accuracy, and visual fatigue. 10 graduate students (23-30 years old; M = 25.6), randomly tested in this experiment, were offered about 25 U.S. dollars for their participation. Numbers in vertical presentation were affected more in vertical vibration than those in horizontal presentation. Analysis showed whenever the display is used in vibration environment, an increased font size may be an effective way to compensate the adverse effect of vibration. The software design of displayed materials must be designed to take the motion effect into consideration to increase the quality of the screen display.

Fitts' law model and target size of pointing devices in a vibration environment.

This study examined models of Fitts' law and effective target widths of three pointing devices in vibration environments. From a research institute 10 employees, ages 26 to 31 years were recruited as paid subjects. Pointing tasks consisted of four square target sizes, four movement distances, and four target angles and were performed on a motion platform using a touch screen, a mouse, and a track ball. The platform simulated two levels of sea wave vibration environments besides a static one. Analysis showed effective target widths increased with vibration, indicating increased variability of the pointing task under vibration. The increase in the track ball was smaller, indicating resistance to motion disturbance. The study also suggests an enlarged target (button) size for the touch screen under the vibration environment. The findings have implications in motor control and human-computer interfacing.

Lifting speed preferences and their effects on the maximal lifting capacity.

The objectives of this study were to evaluate how lifting capacity and subjective preferences are affected by different lifting speeds. The maximum lifting capacity of lift was determined with three independent variables, lifting speed, lifting technique, and lifting height. Questionnaires were evaluated after the experiment by the participants for the lifting speed preferences. This study found that the lifting speed was a significant factor in the lifting capacity (p<0.001); and the lifting height (p<0.001) and the interaction of lifting speed and lifting height (p=0.005) affected the lifting capacity significantly. The maximal lifting capacity was achieved around the optimal speed that was neither too fast nor too slow. Moreover, the participants' preferred lifting speeds were consistently close to the optimal lifting speed. The results showed that the common lifting practice guideline to lift slowly might make the worker unable to generate a large lifting capacity.