1. A method of generating a Completely Automated Public test to Tell Computers and Humans Apart (CAPTCHA), comprising the steps of: storing a database of images and annotations corresponding to the images, each image depicting a concept or object intended for human recognition; distorting at least one of the images, and presenting the distorted image on a computer display along with a separate list of words, one of which best annotates the distorted image; and assuming that the user of the computer is a human as opposed to a machine if the correct word is selected to annotate the distorted image.