The effects of non‐examples on the acquisition of the geometrical concept of semi‐regular polyhedra were examined. Three treatment groups (eight examples only, four examples followed by four non‐examples, four pairs, each pair consisting of an example and a closely related non‐example) viewed a video‐taped presentation. The criterion measure was a 20‐item dichotomously‐scored post‐test. Results favoured the treatments containing both examples and non‐examples. However, the order of presentation of the non‐examples appeared to be negligible.