ABSTRACT
Diagrams are one of the most common ways to represent and communicate geometrical knowledge. Yet, despite the benefits of diagrams, researchers have pointed out that they also present “obstacles children have to overcome in learning about geometry” (Bishop, 1986, p. 150). Presmeg (1986a, 1986b) called these obstacles “difficulties experienced by visualizers,” whereas Hoz (1981) described the “rigidity” that arises when students’ conceptions are limited by the use of diagrams or mental images. These obstacles can be grouped around three themes: diagrams are particular; common usage confuses certain standard diagrams with the classes of objects to which they belong; and a single diagram is often viewed in different ways.
