## 3 Results
### The Effects of Mixtures of Monoterpenes on Human Psychology and Physiology  
Variations in alpha waves and stress index values observed in Exp 2 are shown in Figures 2 and 3, respectively. As shown in Figure 2, the increase in MT concentration caused an increase in alpha waves, indicating that the participants felt relaxed in the presence of MTs, but this response was dose-dependent. All participants showed the most physiological benefit at 20 ppbv MT (mean of the alpha waves = \(15.1\pm 4.0\), refer to Table 1) compared to background conditions (mean of alpha wave = \(9.8\pm 3.0\), refer to Table 1). This pattern was confirmed by the LSD results. The mean values of alpha waves changed significantly (\(p\) value = 0) with increasing concentration of MTs. The increasing alpha patterns were similar for both gender groups (Table 6). Although female olfaction was more sensitive than that of males (obtained from Exp 1), there was no statistically significant (\(p\)-values \(>\) 0.05) difference in mean alpha wave values between males and females. As illustrated in Figure 3, the increase of MT concentrations resulted in the decrease of the stress index values. In addition, the mean background stress index of both male and female participants was \(46.2\pm 6.2\) (refer to Table 1) and was higher at 20 ppbv MT (\(34.7\pm 5.2\), refer to Table 1). This indicates that MT exposure helps reduce human stress. Since the concentrations of MTs were at ppbv levels, their effects must occur via the olfactory processing pathway, not via the blood-borne route through the lungs [28]. The alpha wave data showed that there was also no significant difference (\(p\)-values \(>\) 0.25) in mean stress index between males and females (Table 6). Figure 4 shows variations in alpha waves and stress index with respect to the concentrations of MTs within 2.5 min. The alpha waves of males (slope: 0.292) increased more rapidly than those of females (slope: 0.214). This indicates that the alpha waves of male were more sensitive to inhaling MTs than those of females. On the other hand, the stress index of females (slope: \(-\)0.611) decreased more rapidly than that of males (slope: \(-\)0.497). This indicates that stress in females was reduced \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Parameter** & **Gender** & **n** & **Background** & **7 ppbv** & **15 ppbv** & **20 ppbv** \\ \hline \multirow{3}{*}{Alpha wave} & Male & 3 & 9.3 (\(\pm\) 3.2) & 11.3 (\(\pm\) 3.1) & 13.1 (\(\pm\) 3.3) & 15.4 (\(\pm\) 4.2) \\  & Female & 3 & 10.4 (\(\pm\) 2.7) & 11.8 (\(\pm\) 3.0) & 13.5 (\(\pm\) 3.6) & 14.7 (\(\pm\) 3.8) \\  & \(p\)-value 1  & & 0.319 & 0.696 & 0.746 & 0.626 \\ \hline \multirow{3}{*}{Stress index} & Male & 3 & 45.8 (\(\pm\) 5.5) & 41.5 (\(\pm\) 3.7) & 38.9 (\(\pm\) 4.4) & 35.3 (\(\pm\) 4.8) \\  & Female & 3 & 46.5 (\(\pm\) 7.0) & 41.3 (\(\pm\) 6.3) & 37.0 (\(\pm\) 4.4) & 34.1 (\(\pm\) 5.6) \\  & \(p\)-value 1  & & 0.752 & 0.916 & 0.257 & 0.533 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Mean values of alpha wave and stress indexes of male and female participants obtained from Exp 2. Figure 3: The stress index values from 30 participants (15 male and 15 female) at different monoter concentrations, as obtained from Exp 2.  
more readily by inhaling MTs than in males. Furthermore, when comparing the variations in alpha waves and stress index between males and females as a function of MT concentration, the alpha waves (r\({}^{2}\) = 0.999) and stress index (r\({}^{2}\) = 0.995) of females were slightly more consistent than those of males (alpha wave: r\({}^{2}\) = 0.982; stress index: r\({}^{2}\) = 0.981). This indicates that MT affected female psychology more than male psychology, because the olfactory system of females is more sensitive than that of males [36]. The results obtained from the questionnaires also showed similar psychological patterns (refer to Table 10). Only 44% of the participants felt comfortable before inhaling the MTs. In contrast, after inhaling the MTs, 87% of the participants felt comfortable.