Abstract

Demands on working memory are associated with mental stress, but little is known about the underlying connection between the two. The primary purpose of this study was to quantify individual mental stress, and to monitor heart rate variability (HRV) during high and low working memory (WM) demands influenced by Stroop interference. Another aim was to quantify the performance and response time during the Stroop task and observe their trends during high and low (WM) demands. Finally, the third goal of this thesis was to predict the relationship between mental stress and performance. To this end heart rate was recorded both at rest and while performing the Stroop task. High and low WM demands were obtained by increasing the level of Stroop interference. The response time and performance were calculated for each difficulty level of the Stroop task, as well as during high and low WM demand. The power spectral components HF, LF, LF/HF and the time domain Mean R-R (S), Mean HR (1/min), were used as the components of HRV in the analysis. The results indicated that all the components of HRV examined were sensitive to WM demands. The HF and Mean R-R (S) components decreased with an increase in WM demands from the baseline values. The Mean HR (1/min), LF and the LF/HF ratio increased with increase in demands. Overall, the results indicated a reduction in HRV when higher order cognitive tasks were performed. The response time increased with WM demands. The performance in the Stroop task was decreased with an increase in WM demands. The results also indicated that an increase in WM demand correlates with an increase in an individual‟s stress level, and a decrease in performance level.
The present thesis contributes to the ongoing analysis of human computer interaction in the laboratory environment, and its effects on the autonomic nervous system. It is recommended that future research be conducted at the workplace to better understand the relationship between human computer interaction and mental stress levels.