# Individual Differences in Signal Perception for Takeover Request in Autonomous Driving
## 5 Discussion  
This study aimed to determine how changes in sub-attribute for each modality and personal background affect TOR responses in partially autonomous driving situations. For this purpose, correlation analysis, repeated measure ANOVA, and paired comparison analysis were conducted, and the results are summarized below according to research questions. Research Question 1 focused on examining correlations between reaction times to visual, auditory, and tactile signals and participants' personal backgrounds. The analysis revealed significant correlations between individual background factors and TOR signaling modalities and sub-attributes. Specifically, the faster response times of women to larger auditory stimuli and higher pitch can be attributed to gender differences in auditory perception and sensitivity. Previous research has shown that women tend to have higher sound sensitivity and better discrimination abilities for pitch changes compared to men [35]. These factors may contribute to their faster response times to certain auditory cues in this study. Figure 5: The result of paired comparison analysis for age: (**a**) participants’ responses to how comfortable they were hearing each auditory cue based on their age, A = 500 Hz, B = 1000 Hz, C = 2000 Hz, D = 4000 Hz; (**b**) participants’ responses to how comfortable they were feeling each tactile cue based on their age, A = 1 v, B = 4 v, C = 8 v, D = 12 v; \(y\)-axis indicates ages. Research Question 2 aimed to determine whether there were differences in reaction times to visual, auditory, and tactile signals and their sub-attributes based on participants' personal backgrounds. In terms of visual stimuli, there were minimal age differences. However, for auditory and tactile signals, reaction times increased with age. Notably, the age differences were most pronounced when the amplitude of the tactile stimulus, as well as the loudness and pitch of the auditory stimuli, were at their lowest intensity levels. Regarding the observed increase in reaction times for both auditory and tactile modalities with age, this finding aligns with existing research on age-related changes in sensory perception and cognitive processing. It is well-established that aging is associated with a decline in sensory acuity and cognitive processing speed [22; 38]. Therefore, the slower reaction times in older participants may be attributed to these age-related changes, affecting their ability to detect and respond to the TOR signals. Furthermore, each sub-attribute exhibited a distinct pattern of faster response times as intensity increased. Specifically, a noteworthy observation was made regarding the continuous decrease in reaction times as auditory loudness increased. It was found that for every 10 dB increase in auditory loudness within the range of 50 to 80 dB, participants' reaction times decreased consistently. Similarly, as the frequency of vibration increased from 25 to 50, 200, and 400 Hz, participants' reaction times continued to decrease. Interestingly, there was no significant difference in reaction times between 1000 Hz and 2000 Hz for the pitch of the auditory signal. However, a decrease in reaction time was observed at 4000 Hz. Additionally, no significant difference was found in reaction times between 8 v and 12 v for the amplitude of the tactile signal. These results carry significant implications for future TOR studies. While the criteria for selecting signal intensity in TOR studies may present some ambiguity, findings highlight the crucial role of signal intensity in influencing participants' reaction times. It is important for researchers to carefully select an appropriate level of signal intensity, considering previous studies conducted in similar settings. Furthermore, while auditory signals are relatively well-characterized in terms of pitch and loudness, the same level of detailed characterization is lacking for visual and tactile signals. Consequently, researchers should strive to provide comprehensive descriptions of the signals used in their studies.