People have been altering or improving their memories since before the beginning of recorded history. Oral bards trained themselves to remember and recite long epics as a way of perpetuating cultural memory. In antiquity and the Renaissance there were many memory systems, such as that of Simonides, designed to help speakers remember the main points of their speeches so that they could appear to be speaking extemporaneously rather than reading aloud. Stage actors still train themselves to remember long chunks of dialogue and dancers need to remember the choreography for one- or two-hour long dances. In all these cases, memory is trained by practice.