Here's a lecture by psychologist Barbara Tversky about the understanding of events, spatial cognition, and comics. It's a bit long (an hour) but worth watching. (The parts explicitly about comics start around 25:20. Here's an alternate link where you can jump direct to certain slides)
I've known Barbara and her student John Bresman for many years so it was fun to see. She covers a lot of ground in terms of general cognitive principles at work in the comprehension of sequential images, particularly the more poetic and creative uses of sequential images. I've talked about several of these principles under different terms on this blog and in my papers, and similar lists have been made in various scattered articles for years.
The part of the talk I found most interesting was towards the end, where she describes a recent experiment looking at the depiction of action in panels from comics around the world. On the whole they found that comics from China and America had more action than those from Japan or Italy. The comparison here is that Chinese and English are both languages that can combine the description of an action and the manner by which it happens into one single verb, while Japanese and Italian do not combine these into one verb (i.e. 'to swagger' vs. 'to walk in a swaggering way').
I've wanted to do a study on this comparison for awhile, so I was glad to see the data. It is part of a broader interest that I have in the relationship between thought, verbal language, and visual language.