1. Apparatus for verifying the presence of a particular human individual at a given location by altering and repeatedly assessing details of an iris of an eye of said human individual, said apparatus comprising, in combination: (a) a computer database in which are stored data representing a plurality of images of an iris and other identification data pertaining to each of at least one registered human individual (“RHI”), wherein each of said images is acquired during a different physiologic state of said RHI, each said state influencing said image of said iris; (b) a first processor coupled to the database for accessing selected information from the database and for producing at least one prompt signal; (c) at least one first camera arranged (1) to view an iris of a putative human individual (“PHI”), and (2) to generate a plurality of test images of said iris of said PHI for transmission to said first processor; (d) a prompt producing device, for producing at least one prompt in response to said at least one prompt signal received from said first processor, for inducing at least one involuntary anatomic change in said iris of said PHI; wherein said first processor is operative to: (1) generate said at least one prompt signal for transmission to said prompt producing device, and thereafter generate at least one representation of at least one post-prompt test image of said iris; and (2) compare: (a) data representing (i) at least one of said at least one post-prompt test image, and (ii) at least one other test image of said iris of said PHI received from said at least one first camera, with (b) data representing said stored images of the iris of said at least one RHI; to verify the identity of the PHI; thereby to verify that the PHI is the same individual as one of said at least one RHI by assessing said PHI iris during a plurality of physiologic states, or to determine that the PHI is not the same individual as any one of said at least one RHI.