Most computer interfaces are designed in a one-size-fits-all fashion, which does not account for individual differences in abilities and preferences. Some computer users thrive with one software application while another user may struggle to use the same software. Some people tend to perform very well amidst distraction whereas others have a difficult time concentrating on a primary task when distracting agents are present. Much work has been done in quantifying a person's performance, but it has typically been difficult to quantify how difficult a task was for a person to perform. This thesis looks into the stress exhibited by various computer users while performing tasks in both their preferred and non-preferred modalities. The paper surveys the current physiological methods for analyzing human stress and delineates the hardware and software design and implementation of some of these methods. The physiological data-collecting hardware and software were deployed to collect physiological samples from test subjects engaging in memorization and recollection tasks in both an undistracted and a distracted setting. An analysis of the data shows the correlation between preferred modality and performance of tasks in that modality and other modalities. This analysis also shows the correlation between user arousal level and performance with and without distraction. Individual differences are considered by normalizing the physiological data collected for each subject prior to comparison with other subjects. The work presented herein gives insight into the individual differences of various types of computer users and is a precursor to work in adaptive user interface technology. / Master of Science