A large body of research has shown that incorporating text in the corresponding sections of an illustration facilitates the learning of illustrated documents. More recently, a series of studies has revealed that the use of interactive windows located close to the illustration causes similar effects. The aim of this paper is to help bring about a better understanding of the beneficial effects of these pop-up windows on multimedia learning. The first study shows that the spatial integration of these windows has a positive effect on performances in tasks designed to evaluate, in particular, the quality of the referential connections between the text and the illustration and, additionally, that their interactive characteristics also contribute to learning. The second study shows that this specific advantage seems to be due to the intermittent nature of these windows which makes it possible to reduce the visual perceptual load of the document. (Contains 5 tables and 2 figures.)