Researchers have pointed out the need to find an alternative to subjective questionnaires to measure presence in a virtual environment. Situational awareness has been proposed to objectively measure the concept of presence. However, the link between situational awareness and specific factors of presence has not been established. To study this relationship, 60 participants executed a driving task in a virtual environment under different visual conditions while we measured their situational awareness with the situational awareness global assessment technique (SAGAT), and their presence with the presence questionnaire (PQ). During the driving task, we objectively and meaningfully manipulated immersion, a factor of presence, by varying our participants' contrast sensitivity, size of the field of view, and visual acuity. The meaningful manipulation of presence also allowed us to evaluate the functional thresholds of the three aforementioned visual qualities for a driving task, which were previously measured from a multidirectional selection test. Our results indicated a significant positive correlation between SAGAT and PQ. They also showed that SAGAT was sensitive to an immersion's degradation and brought a good diagnosticity on the effect of an immersion's manipulation. Consequently, we conclude that it could represent an objective alternative to subjective questionnaires to measure presence in a virtual environment. Moreover, our assessment of the functional thresholds allowed us to confirm that they were context dependent. Our results indicated that only the contrast sensitivity functional threshold was valid in both a multidirectional selection test and a driving task.

Psychophysiological indicators have garnered significant interest in the assessment of presence . However, despite this interest, the nature of the relationship between psychophysiological indicators and presence factors remains undetermined. Presence, the perceived realness of a mediated or virtual experience, is modulated by two factors: immersion and coherence. Immersion represents the extent and precision of the simulated sensory modalities, while coherence refers to the environment's ability to behave as expected by the user. To study the relationship between psychophysiological indicators and presence factors, we objectively manipulated immersion by altering three visual qualities. The visual qualities were set to values above, at, or below their functional threshold. These thresholds are defined as a perceptual boundary under which a sensory quality value should be considered functionally degraded. Sixty participants performed a driving task in a virtual environment under the aforementioned conditions, while we measured their cardiovascular and eye responses. We found that degraded immersion conditions yielded significantly different psychophysiological indicator results than the condition without degradation. However, we observed an effect of immersion degradation on our measured variables only when the visual conditions were set below the functional threshold. Manipulations of immersion below the functional threshold introduced unreasonable circumstances which modified our participants' behavior. Thus, our findings suggest a direct impact of immersion on coherence and highlight the sensitivity of psychophysiological indicators to the coherence of a virtual environment. These results have theoretical implications, as a presence concepts relationship model should include the direct impact of immersion on coherence.

We consider that to objectively measure immersion, one needs to assess how each sensory quality is reproduced in a virtual environment. In this perspective, we introduce the concept of functional threshold which corresponds to the value at which a sensory quality can be degraded without being noticed by the user of a virtual environment. We suggest that the perceived realism of a virtual experience can potentially be evoked for sensory qualities values ranging from the perceptual threshold to the functional threshold. Thus, the identification of functional thresholds values allows us to constrain immersion. To lay the foundation for the identification of functional thresholds, we applied a modified version of the method of limits. We measured the value at which 30 participants were able to identify the degradation of their field of view (FOV), visual acuity, and contrast sensitivity while executing a multidirectional selection test. This enabled us to identify functional perceptual thresholds of 96.6 degrees for FOV, 12.2 arcmin for visual acuity, and 25.6% for contrast sensitivity.