Interviews were used to find the frequency of different types of errors made by 95 sixth-year Papua New Guinea students on a mathematics test. The general trend was the same as for western students, but the Papua New Guinea students made far fewer careless errors. (MNS)

This experiment involved 176 London children aged six and seven. Their levels of attainment on subtraction were quickly and accurately established by two questions. Then teaching programs were used to help them attain prerequisite skills. To symbolize too soon is a danger to be avoided. (MNS)

The evidence suggests that students in grades 5 through 8 have difficulty relating isometric type drawings to the rectangular solids they represent. Errors made by students were analyzed and the effect of instruction in spatial visualization activities assessed. (MNS)

The process of transition from a novice's state to that of an expert, in the domain of decimals, is described in terms of explicit, intermediate, and transitional rules which are consistent yet erroneous. Data from students in grades 6-9 are included. (MNS)

Diagnostic interviews were conducted with third graders to determine why they made mistakes on sixteen arithmetical tasks. A modified version of the Newman method of analyzing errors is discussed and applied to these interviews. (MP)