## 5 Measurement and Parameters Selection
### Subjective Measurements  
Subjectively measuring embodiment is significant to understanding the perception of the sense of presence in virtual environments. To do so, the scientific literature proposed a consistent number of questionnaires and methodologies that explored the perceivedlevel of embodiment. In this regard, the Embodiment questionnaire [33] was the only one aimed at directly assessing the sense of embodiment and has a form adapted from the one proposed by [PERSON] and colleagues [65] and [PERSON] and colleagues [66]. Such a questionnaire contains questions relating to two features of embodiment, namely, self-embodiment and spatial embodiment. The first aspect was defined as the extent to which the participant perceives a virtual body component, while the second one represented the degree to which the participant feels immersed in the virtual environment. Another key tool identified in scientific literature for collecting subjective data on embodiment is the Presence Questionnaire, adapted from [PERSON] and [PERSON] [34] and revised by the UQO Cyberpsychology Laboratory. This questionnaire presents targeted questions to evaluate the realism of the virtual environment, the participant's ability to act within it, the quality of the interface, and the participant's self-assessment of performance. The considered scientific works highlighted other subjective measurements for the sense of presence evaluation, such as the IGroup Presence Questionnaire (IPQ). Such a questionnaire provided a subjective measure of the perception of being within a virtual environment [67; 68]. Among the considered works, it was proposed as divided into four subscales: general presence, spatial presence, involvement, and realness. Similarly, the Slater-Usoh-Steed (SUS) questionnaire [67] corresponds to a validated method comprising six statements, which are evaluated on a seven-point Likert scale. This approach includes the participant's sense of being inside the simulated environment, the degree to which the environmental simulation is considered the dominant reality, and how far the simulated environment is remembered as a place. It is often used in conjunction with the Presence Questionnaire (PQ) developed by [PERSON] [34]. Within experiments requiring emotional involvement of the participant, which constitute a consistent portion of the considered scientific works within the present review, participants were asked to complete the Self-Assessment Manikin (SAM) [69], a non-verbal, image-based questionnaire designed to assess the emotional reactions of subjects, to measure a person's affection and feelings in response to an object or event. In the context of perceived emotions and feelings' impact on embodiment in MR, it is crucial to subjectively assess the participants' state of anxiety and the cognitive and psychological workload during the virtual experience. In this regard, the State-Trait Anxiety Inventory (STAI) [70] is a psychological inventory comprising 40 self-assessment questions on a four-point Likert scale. It gauges two types of anxiety: state anxiety and trait anxiety. Similarly, more recent research was performed by including within the experimental measurements collection the Profile of Mood States (POMS) [71] and Social Avoidance and Distress (SAD) [72]. Moreover, the considered gold standard by the scientific community for assessing cognitive and psychological workload is the NASA Task Load Index (TLX) [73]. The following Table 2 includes all the subjective questionnaires related to embodiment and the sense of presence assessment in MR that emerged from the scientific literature review: