Framework of reference: A woman conducting a survey into sexual behavior was questioning an airline pilot. She asked him, finally, when he had last made love. He replied, “1956.” She was most surprised, pilots being what they are. “Nineteen fifty-six?” she asked. “Well it’s only 2216 now,” he replied, looking at his watch. A joke involves a sudden switch from one framework of reference to another. This sudden switch of frames of reference is the kind of lateral thinking that can often generate creative ideas.