Clement tries to organize some findings concerning the errors students make involving speed-time and distance-time graphs. He detects (i) a slope-height confusing: given two linear distance-time graphs in one picture that intersect at t =4, students were asked which of the two objects travels faster at t = 2, as many as half of the students answered the slower one (which had traveled more at the time). (ii) Treating the graph as a picture: (a) making a figurative correspondence between the shape of the graph and some visual characteristics of the problem scene (eg. speed-time graph for a bicycle traveling over a hill), and (b) connecting local visual features of the problem scene to similar features of the graph (eg. same location and crossing speed-time graphs). Clement calls these errors non-standard symbolization strategies.