The following are but a few instances of our everyday experiences in which the magical, almost hypnotic, effects of repetition operate: the exciting spectacle of marching soldiers in the same dress, same step and same attitude; the fascination of neatly arranged flower beds of like color, structure, and texture; the impressive sight of crowds at football games, theaters, public demonstrations; the satisfaction we derive from the geometric patterns created by ballet dancers and chorus girls with identical costumes and movements; the feeling of order evoked by rows of methodically placed packages on the grocer's shelf; the comforting effect of the regularity of repeating patterns in textiles and wallpapers; the excitement we experience at the sight of plane formations or migrating flocks of birds.