1. A user authentication system for permitting user access to a computer controlled device through an access procedure, comprising: A) a display device for displaying a group of items to said user, said group of items comprising: 1. user known items, and 2. user unknown items, B) an input selection device for receiving input from the user, wherein said user input indicates the presence of or absence of known items within said group of items, wherein said user input is made without identifying which items within said group are known and which items within said group are unknown, C) a control computer programmed to automatically compare said user input to a predetermined answer that indicates the presence of and absence of known items within said group of items. D) an access device for allowing access when said user's input correctly indicates the presence of and absence of known items within said group of items, wherein said group of items includes a plurality of subgroups, wherein at least one of said plurality of subgroups includes at least one known item, wherein said user input comprises an identification of a subgroup within said plurality of subgroups with the largest number of known items.