The authors used an eyetracking device to measure where people's eyes look when they are reading individual comic panels (as opposed to across a whole page), as well as photographs taken by experts, amateur photographers and a robot.
They found that participants had far more directed and consistent eye movements towards specific portions of comic panels than were found for photographs, where gaze was far more general. They suggest that these findings show that comic panels direct the flow of attention of their readers.
I am not sure that these findings fully support their goal to see if "artists purposefully direct the visual attention of readers through the pictorial narrative." This is a fairly vague hypothesis (direct visual attention to what? To the whole image? What does that mean?). For full evidence of this hypothesis, they would need to see the relationship between eye movements across a larger page layout with those in individual panels, assuming that this is what they mean by directing a reader's attention through the narrative.
What's appealing about these data though is the idea that panels—being created to be in sequence—hone a reader's attention to specific parts of panels over others. This is an important finding, and invites follow up experiments that might better explore just what portions of panels might be important or not for the comprehension of a sequence.
More equivalent stimuli might be able to ask: Would photo versions of panels (as in a photo novella) elicit the same types of eye movements as those in drawn panels? What if the photos also showed figures engaged in actions instead of places)? How are eye movements of comic panels different from other artwork or film shots (where all are designed, but only comics and film intentionally have a sequence)?
It seems that these would be more equivalent comparisons, otherwise it seems like comparing apples and oranges: the stimuli are totally different from each other in nature to begin with. The more important comparison shouldn't be comic panels vs. photos, it has to bear in mind the content of those images.
Comics are a compelling, though complex, visual storytelling medium. Researchers are interested in the process of comic art creation to be able to automatically tell new stories, and also, summarize videos and catalog large collections of photographs for example. A primary organizing principle used by artists to lay out the components of comic art (panels, word bubbles, objects inside each panel) is to lead the viewer's attention along a deliberate visual route that reveals the narrative. If artists are successful in leading viewer attention, then their intended visual route would be accessible through recorded viewer attention, i.e., eyetracking data. In this paper, we conduct an experiment to verify if artists are successful in their goal of leading viewer gaze. We eyetrack viewers on images taken from comic books, as well as photographs taken by experts, amateur photographers and a robot. Our data analyses show that there is increased consistency in viewer gaze for comic pictures versus photographs taken by a robot and by amateur photographers, thus confirming that comic artists do indeed direct the flow of viewer attention.
Jain, Eakta, Sheikh, Yaser, & Jessica Hodgins (2012). Inferring Artistic Intention in Comic Art through Viewer Gaze SAP '12 Proceedings of the ACM Symposium on Applied Perception, 55-62 : 10.1145/2338676.2338688