D. Keyson et al. (Eds.): AmI 2011, LNCS 7040, pp. 41–50, 2011. © Springer-Verlag Berlin Heidelberg 2011 A Wearable User Interface for Measuring Reaction Time Burcu Cinaz, Christian Vogt, Bert Arnrich, and Gerhard Tröster ETH Zurich, Electronics Laboratory, Gloriastrasse 35, 8092 Zurich, Switzerland Burcu.Cinaz@ife.ee.ethz.ch Abstract. Reaction time (RT) tests are known as simple and sensitive tests for detecting variation in cognitive efficiency. RT tests measure the elapsed time between a stimulus and the individual's response to it. A drawback of existing RT tests is that they require the full attention of a test person which prohibits the measurement of cognitive efficiency during daily routine tasks. In this contribution we present the design and the evaluation of a wearable RT test user interface which can be operated throughout everyday life. We designed a wear- able watch-like device which combines the generation of a haptic stimulus and the recognition of subject’s hand movement response. In order to show to what extent the wearable RT test is convenient to measure reaction times, we de- signed an experiment in which we measured the reaction times of ten subjects from two different setups. In the first half of the experiment, the participants performed a desktop-based RT test whereas in the second half of the experi- ment they performed the wearable RT test. In order to measure changes in the duration and variability of reaction times we induced additional cognitive load in both setups. We show that individual changes of reaction times occurred due to the cognitive load manipulation are similar for both desktop-based and wear- able RT test. Additionally we investigate the subjective ratings of perceived workload. We conclude that the presented wearable RT test allows to measure changes in reaction times occurred due to additional cognitive load and hence would allow the assessment of changes in cognitive efficiency throughout everyday life. Keywords: reaction time, wearable user interface, cognitive efficiency. 1 Introduction and Motivation Reaction time (RT) tests measure how rapidly information can be processed and a response to it can be activated [14]. In other words, RT tests measure the elapsed time between a stimulus and the individual's response to it. According to Jensen [10], RT tests are well suited for cognitive assessment tests since in comparison to convention- al psychometric techniques, RT tests offer a high sensitivity for detecting variation in cognitive efficiency and they can be virtually unlimited repeated. Several desktop- based RT tests have been developed in which users have to respond to visual stimuli by using keyboard, mouse or special buttons. An extensive review about computer- based cognitive tests can be found in [20]. There are several examples on applying RT tests to assess cognitive functioning: early detection of cognitive decline such as