Perseveration in healthy subjects: an impressive classroom demonstration for educational purposes.

Perseveration, that is, the inappropriate maintenance of an activity, is not exclusively observed in patients with brain pathology. We present a brief calculation task that requires healthy subjects to add eight numbers sequentially. While the first seven steps of the addition involve the repeated application of a particular rule, this rule does not apply for the last step. However, a high percentage of subjects (approximately 70%) will commit a perseverative error at this last step and hence obtain an incorrect final result. This simple task is a highly informative illustration of the principle of perseverative behavior. When applied in a classroom setting, it is an impressive demonstration of the ease with which perseveration can be evoked in healthy persons.