A possible (somewhat sci-fi) future extension to this idea would be directly monitoring the brain of the subject, in conjunction with eye movements, in an attempt to quickly detect a subconscious signal of 'recognition' while scanning the computer-generated faces. Might be that certain signals in the brainwave (e.g. the P300 or something similar: http://en.wikipedia.org/wiki/P300_%28neuroscience%29 ) could be used for this purpose.