Acta Polytechnica Hungarica Vol. 8, No. 5, 2011 – 205 – Heart Rate Variability Monitoring during Human-Computer Interaction Károly Hercegfi Department of Ergonomics and Psychology, Budapest University of Technology and Economics Magyar tudósok krt. 2, Bldg. Q H-1117 Budapest, Hungary hercegfi@erg.bme.hu Abstract: This paper outlines a Heart Rate Variability (HRV)-based method applicable to Human-Computer Interaction (HCI) researches. After a brief overview of various psychophysiology-based empirical techniques (mainly focusing on the mental effort approach), a recent research is shown. The paper presents new results of a short, basic series of experiments, attempting to explore the boundaries of the temporal resolution of the method. The applied INTERFACE methodology is based on the simultaneous assessment of HRV and other data. The results raise hope that this methodology is potentially capable of exploring mechanisms underlying practical usability issues and identifying quality attributes of software elements – over the previously developed HRV- based methods – with a temporal resolution of only a few seconds. Keywords: Human-Computer Interaction (HCI); software usability testing and evaluation; empirical methods; Heart Rate Variability (HRV) 1 Introduction To assess the quality of software products, one of the most important keywords is usability. A highlighted usability factor is the mental effort required by current Human-Computer Interaction (HCI). In some definitions of usability as a quality dimension of software products – as it is laid down, e.g., in the original version of the international standard of software product evaluation (ISO/IEC 9126:1991 [1]) – the required mental effort appears not only as a metric, but it is the core of the definition: better quality means that less effort is needed for the usage of the particular software. Evidently, in addition to subjective methods such as questionnaires, objective methods are also needed to measure mental effort (self-imposed mental work stress).