Neural responses to a repeated stimulus typically diminish, an effect known as repetition suppression. When a single visual stimulus (e.g., letter of the alphabet, word, object, face) is serially flashed in different locations of a display, several stimuli appear to be present simultaneously due to an effect known as persistence of vision. Normal human observers' estimates of how many stimuli they perceived at any instant of time are significantly lower when the same stimulus is flashed repeatedly than when a different stimulus is used for each flash. This is a result of the brain's diminishing response (repetition suppression) to the repeated stimuli. The present invention generally relates to methods for assessing the normality of neural performance, particularly as relates to the integrity of cortical inhibition, visual persistence, proliferation effect, and repetition suppression. Deficits in repetition suppression serve as early and confirmatory measures of cognitive disorders such as schizophrenia.