An early experiment on knowledge of results was the machine invented by Sidney Pressey, where a device both tested and taught multiple-choice questions.
The material was multiple choice items, and the method used as an addition to collecting classroom test scores.
Undoubtedly, the set-up had given extra practice on the questions as well as knowledge of results, and the experiments often confounded the two factors.
Using a teaching program on decimal arithmetic, an experienced teacher can put student mistakes into types.
For example, one group of mistakes are due to the learners not understanding the rules about placement of the point in decimal multiplication.
[11]: 10 This is also shown by experiments on animal learning which show the effects of knowledge of results on later behaviour.