# Collaborative Use of a Shared System Interface:
## 6 Discussion
### Predictive Validity  
In line with our hypotheses, we observed that, the greater the GC of dyads, the better they performed on the Change Blindness task. As suggested in the literature, looking at the same locations reduced coordination efforts and incidents [9; 34], facilitating better achievement of the dyad's task at hand [32; 35; 36; 56]. As mentioned earlier, high performance related to answer accuracy and short trial completion time. Differences in trial completion time revealed that globally two main scenario types were observed. Dyads spending a lot of time performing the task generally ended up giving up or choosing the wrong answer. However, dyads who were fast in performing the image difference identification task generally found the right answer. In this scenario, GC was high because dyads' collaboration helped them visually converge together towards the target quickly. It may be that, for instance, as the two dyad members had to both be ready before they could move to the question, the dyad member finding the answer first and quickly was efficient in making his/her partner find it on the screen. Pehaps dyad communication influenced dyad GC, which was positively associated with higher performance. However, because our second experimental study aimed at demonstrating predictive validity of the GC index, we focus on dyad GC as an independent variable.  
Also in line with our hypotheses, the greater the GC of dyads, the lesser cognitive load they exhibited. Actually, as literature suggests, during interactions between two persons, gaze direction is special in producing shift of attention on the other person [57; 58]. Hence in our context, at any time during interactions within a dyad, a dyad member's gazing at a location of the screen is likely to shift the other member's gaze to the same location when the former communicates to the later where he or she intends to look at. This behavior was typical and recurrent during dyad collaboration in Study 2. When dyad members interacted during the experimental task (e.g., discussing a specific visual element in the system interface), they were thus likely to look in the same regions of the screen to indicate to each other what their actions or words refer to on the interface. It may be that, knowing that the other dyad member looked at the same location during interaction reduced the cognitive load needed to make him or her shift attention to specific regions of the shared interface. A reason may be that looking at the same regions on the screen improves harmonization of dyad members' mental models of the shared system interface [33]. Moreover, because shifting their partner's attention and gaze to screen areas required communication, faulty communication between dyad members during the task likely led to lower gaze convergence and longer times taken to look at and process the image before answering the related question. The longer they visually processed the image the more cognitive resources it took them to perform the task, that is, the higher their cognitive load. This logic applies to all trials, whether a dyad found the right answer or not, and whatever the length of time the dyad took to complete the trial. However, no association was found between the trial analysis time and cognitive load. Hence, perhaps this finding can be explained by the fact that it is more the actual visual processing of the image than the time looking at it that impacted user cognitive load. Moreover, participants were more likely to visually process the images to a greater extent when they spent more time looking at the images.