a neuropsychological technique aimed at assessing the ability to recognize and compare unfamiliar human faces. Subjects are shown photographs of faces and asked to identify or correlate them when conditions change – lighting, angle or expression. The test assesses the perceptual processing of faces rather than memory of familiar people, and is often used to diagnose prosopagnosia (facial blindness) or other visual-perceptual disorders. It is also used in research on social cognition and brain function, especially in relation to the function of the fusiform gyrus.