an automated test to tell computers and humans apart is disclosed , comprising displaying on a computer screen an animation comprising of a foreground and a background , one of the foreground comprising a plurality of typographical characters and the other comprising partial obstruction of the typographical characters , and wherein the animation comprises relative motion between the background and foreground . the automated test may comprise displaying on a computer screen an image , and requiring the user to perform operation on the image to resolve an encoded solution . the test may also comprise displaying on a computer screen a video clip , and requiring a user to provide an input corresponding to subject matter presented in the video clip .