Despite the ubiquitous use of diagrams to convey information and support reasoning, there has, until now, been no consensus about why a diagram can be successfully used. Scientists in France, as part of the 'Diagram based reasoning' (DBR) project, have revealed the advantages of diagrams over linguistic representations, insisting that their findings will have immediate and far-reaching consequences for teaching practices. To reach their conclusions, the DBR research team carried out a series of experiments, including an analysis of various diagrams to draw up a classification system. Hence, the diagrams were divided into two categories. The first group was made up of those diagrams with a 'static' use: the user simply extracts a piece of information from the diagram and for this reason the diagram promotes her memory. The second group included diagrams with the 'more interesting' dynamic use, whereby the user infers some new piece of information from the diagram, and does that by modifying or 'manipulating' it. Within these two categories, the DBR researchers further distinguished between the diagrams according to the degree of correspondence between the particular diagrammatic format and the structure of data conveyed by a particular diagrammatic format. The researchers then graded the correspondence: for example, linguistic descriptions were graded as having zero degree of correspondence and scientific images a very high degree of correspondence. Other experiments were carried out to evaluate the inferential power of the use of diagrams. The DBR research team found that drawings, namely graphs and sketches, improved a person's performance when she was answering questions involving 'visuo-spatial reasoning about non-manipulable objects'. The scientists therefore concluded that 'the use of images in education should be seriously scrutinised'.