an easily administered , non - invasive , sensitive and specific system and method for screening persons for dementia , particularly dementia of the alzheimer &# 39 ; s type , is provided . the system and method include means for irradiating the eye of a person with light , preferably light solely within the infrared spectrum , and means for generating a signal responsive to the amount of light reflected from the eye over a period of time . this signal is indicative of changes in the pupil &# 39 ; s size over time . the system and method further include means for performing a fourier transform upon this signal to provide a value indicative of the strength of this signal &# 39 ; s frequency components . this value then is compared against a predetermined threshold value and , if this threshold value is exceeded , a higher probability is assigned to the person having dementia , particularly dementia of the alzheimer &# 39 ; s type .