  Traditional cinematography has relied for over a century on a
well-established set of editing rules, called continuity editing, to create a
sense of situational continuity. Despite massive changes in visual content
across cuts, viewers in general experience no trouble perceiving the
discontinuous flow of information as a coherent set of events. However, Virtual
Reality (VR) movies are intrinsically different from traditional movies in that
the viewer controls the camera orientation at all times. As a consequence,
common editing techniques that rely on camera orientations, zooms, etc., cannot
be used. In this paper we investigate key relevant questions to understand how
well traditional movie editing carries over to VR. To do so, we rely on recent
cognition studies and the event segmentation theory, which states that our
brains segment continuous actions into a series of discrete, meaningful events.
We first replicate one of these studies to assess whether the predictions of
such theory can be applied to VR. We next gather gaze data from viewers
watching VR videos containing different edits with varying parameters, and
provide the first systematic analysis of viewers' behavior and the perception
of continuity in VR. From this analysis we make a series of relevant findings;
for instance, our data suggests that predictions from the cognitive event
segmentation theory are useful guides for VR editing; that different types of
edits are equally well understood in terms of continuity; and that spatial
misalignments between regions of interest at the edit boundaries favor a more
exploratory behavior even after viewers have fixated on a new region of
interest. In addition, we propose a number of metrics to describe viewers'
attentional behavior in VR. We believe the insights derived from our work can
be useful as guidelines for VR content creation.
