Eyetrack videos - iPad vs newspaper
French consulting firm Miratech has released some eyetrack videos measuring how someone reads the iPad vs. a newspaper.
Among its conclusions is that people concentrate more on print stories and have better recall.
Keep in mind, however, that these things tend to be era-specific. Tablets, etc., are still rather new formats. As their ergonomics and visual grammar are "learned," results are likely to shift as we've seen with some studies on linking.