## 3 Results
### Specific Findings
#### 3.2.2 Driver Emotion Modulation Based on Unisensory and Multisensory Inputs
Positive comments can also reduce a driver's state of anger, thereby enhancing driving performance [69; 71]. Conversely, angry speech tends to increase reaction times, likely by activating the right frontoparietal networks and reducing activity in the left frontal area [17; 70]. In addition, studies have shown that music, especially self-selected music, can potentially mitigate anger [62; 63; 66; 68]. Low-activation music reduces systolic reactivity and influences cardiovascular responses, moderating the cardiovascular correlates of negative moods [29; 73]. Ref. [74] also demonstrated that selecting the optimal decibel level in the car can effectively reduce drivers' negative emotions. From an olfactory standpoint, olfactory notifications are less distracting and more helpful than visual ones, with scents like rose and peppermint improving drivers' mood and behavior [76; 77]. Conversely, ref. [78] reported that unpleasant scents can worsen driving performance, while clean air has a neutral effect. Ref. [79] also indicated that olfactory cues were more effective than visual ones. Furthermore, ref. [80] examined the effects of three olfactory stimulants (lavender, sweet orange, and agarwood) on negative emotions. Their results indicate that agarwood has the best regulatory effect on negative emotions, followed by sweet orange, with lavelander being the least effective. From a temperature viewpoint, comfort levels are partially dependent on the duration of cooling. Ref. [75] mentioned that longer cooling duration has been shown to effectively reduce passive fatigue, as evidenced by changes in physiological measures such as heart rate variability and skin temperature. However, ref. [11] summarized that cooling can also result in a subjective reduction in feelings of fatigue, which may lead drivers to prefer more stimulating driving experiences. Most of the included studies do not mention how cultural factors influence the emotion modulation process, with only a few articles highlighting the need for culturally sensitive design (\(n=4\), 12%) [11; 53; 73; 82]. From a human factor perspective, several studies have pointed out that individual differences affect driving style and, thus, the effectiveness of driver emotion regulation [11; 53; 55; 59; 64; 81]. Moreover, studies indicate that sensory-based driver emotion modulation can alter human cognition, influencing modulation outcomes [4; 52; 62; 74; 80]. Meanwhile, refs. [71; 75; 77; 79] observed that that physiological differences resulting from emotion regulation can also affect driver behavior. Based on the literature survey, it is evident that individual differences play a vital role in emotion modulation strategies for drivers. It is worth noting that human cognition can effectively reduce negative emotions and enhance driving performance. This suggests the potential benefits of improving physiological sensing to enhance in-vehicle user experience. Hence, there is a serious need to strengthen communication between humans and in-vehicle systems and to better manage attention allocation while driving.