# Camera-Sourced Heart Rate Synchronicity: A Measure of Immersion in Audiovisual Experiences
## 5 Discussion  
The hypothesis for this study is that the increase in immersion influenced by a high-end audio presentation, compared with a basic audio presentation, can be measured using a camera-sourced ISC-HR feature. The results suggest that no such influence was elicited, as assessed using a camera-sourced ISC-HR feature, an equivalent ECG-sourced feature, and an immersion self-report questionnaire. However, the intercorrelation of these three measures suggests that camera-sourced ISC-HR is a viable means for assessing immersion. Specifically, the statistically significant correlation between the camera-sourced and the equivalent ECG-sourced ISC-HR features shows that the camera approach was accurate in this study. The statistically significant correlation between both ISC-HR features and the validated immersion self-report score, once two statistical outliers are removed, shows that the measures index each other. These findings supplement previous research demonstrating correlations between ISC-HR features and self-report scores for immersion [9; 10], attentional engagement [11; 12], and flow [13]. However, this study introduces a novel contribution by using a camera to acquire ISC-HR data, a method not previously explored. To validate this approach further, additional research should assess the generalisability of using camera-sourced  
Figure 6: The positive relationship between immersion score and ISC-HR is shown. The same two statistical outliers are visible in the top-left and bottom-right quadrants. Linear regression lines have been added using the least squares error method, and their overlapping highlights the similarity of the two distributions. ISC-HR features for measuring immersion across diverse populations. In particular, it is crucial to explore the effectiveness of this method for participants with darker skin tones, as this demographic was underrepresented in our sample and darker skin tones can affect the accuracy of camera-sourced HR measurements [74]. When considering this research, alternative and emerging methods for obtaining heart rates from video may be used to enhance robustness and reliability. Some of these methods may be implementable using PyVHR, the software used in this study, as it is still under active development [47]. The camera-based approach is desirable as it is fully non-contact. It is also desirable as it has the potential to unlock alternative features that provide insight into patrons' feelings of immersion. Both the ISC of facial actions [75] and ISC of gaze location [76] are promising emerging measures for assessing audiovisual experiences, which may be captured using the camera configuration used in this study. However, although the self-report data revealed that the camera and the ECG sensor affect the viewing experience to a similar extent, the bright lighting required for the camera's operation has a markedly more adverse impact than the ECG sensor. Hence, we suggest that future research should focus on how the camera may be deployed more discretely as well as the viability of obtaining psychologically indicative features in low-light conditions. Addressing these considerations will allow for a more naturalistic assessment of audiovisual experiences, where participants feel more comfortable. Regarding the validity of the measurement instruments, there are some concerns that the questionnaire may not allow for the reliable self-assessment of immersion. Only eleven respondents strongly agreed with the statement \"I found all questions easy to understand\" and Items 12 and 20 from the Film IEQ were highlighted as sub-optimal. The presence of outliers and the imperfect correlation between the ISC-HR features and the immersion self-report scores also raise some concerns and suggest that ISC-HR is not a replacement for an immersion questionnaire. Upon reflection, immersion may not be the closest associated attribute to ISC features, as they are more objective measures of shared experience [75].