Stages in diagram development
A sizable proportion of the pupils were unable to succeed even with the authors' diagrams in the primary school study. The authors' diagrams were all at the symbolic end of the continuum described earlier. The authors diagram fo Problem 1 is shown below) it could well be the case that some children were not ready for such representations and yet might have been able to interpret a more physical or literal version. This leads us to conjecture that children may need to progress through stages of development in the drawing and interpretation of diagrams for problem-solving. They need to move from a concrete form of representation to a more symbolic form.