@article{li_bahn_nam_lee_2014, title={Effects of Luminosity Contrast and Stimulus Duration on User Performance and Preference in a P300-Based Brain-Computer Interface}, volume={30}, ISSN={["1532-7590"]}, DOI={10.1080/10447318.2013.839903}, abstractNote={Brain–computer interfaces (BCI) have potential to provide a new channel of communication and control for people with severe motor disabilities. Although many empirical studies exist, few have specifically evaluated the impact of contributing factors on user performance and perception in BCI applications, especially for users with motor disabilities. This article reports the effects of luminosity contrast and stimulus duration on user performance and usage preference in a P300-based BCI application, P300 Speller. Ten participants with neuromuscular disabilities (amyotrophic lateral sclerosis and cerebral palsy) and 10 able-bodied participants were asked to spell six 10-character phrases in the P300 Speller. The overall accuracy was 76.5% for the able-bodied participants and 26.8% for participants with motor disabilities. The results showed that luminosity contrast and stimulus duration have significant effects on user performance. In addition, participants preferred high luminosity contrast with middle or short stimulus duration. However, these effects on user performance and preference varied for participants with and without motor disabilities. The results also indicated that although most participants with motor disabilities can establish BCI control, BCI illiteracy does exist. These results of the study should provide insights into the future research of the BCI systems, especially the real-world applicability of the BCI applications as a nonmuscular communication and control system for people with severe motor disabilities.}, number={2}, journal={INTERNATIONAL JOURNAL OF HUMAN-COMPUTER INTERACTION}, author={Li, Yueqing and Bahn, Sangwoo and Nam, Chang S. and Lee, Jungnyun}, year={2014}, month={Feb}, pages={151–163} }
 @article{nam_li_yamaguchi_smith-jackson_2012, title={Haptic User Interfaces for the Visually Impaired: Implications for Haptically Enhanced Science Learning Systems}, volume={28}, ISSN={["1532-7590"]}, DOI={10.1080/10447318.2012.661357}, abstractNote={The overall quality of haptic user interfaces designed to support visually impaired students' science learning through sensorial feedback was systematically studied to investigate task performance and user behavior. Fourteen 6th- to 11th-grade students with visual impairments recruited from a state-funded blind school were asked to perform three main tasks (i.e., menu selection, structure exploration, and force recognition) using haptic user interfaces and a haptic device. This study used several dependent measures that are categorized into three types of variables: (a) task performance including success rate, workload, and task completion time; (b) user behavior defined as cursor movements proportionately represented from the user's cursor positional data; and (c) user preference. Results showed that interface type has significant effects on task performance, user behavior, and user preference, with varying degree of impact to participants with severe visual impairments performing the tasks. The results of this study as well as a set of refined design guidelines and principles should provide insights to the future research of haptic user interfaces that can be used when developing haptically enhanced science learning systems for the visually impaired.}, number={12}, journal={INTERNATIONAL JOURNAL OF HUMAN-COMPUTER INTERACTION}, author={Nam, Chang S. and Li, Yueqing and Yamaguchi, Takehiko and Smith-Jackson, Tonya L.}, year={2012}, pages={784–798} }