Mental state analysis is performed by obtaining video of an individual as the individual interacts with a computer, either by performing various operations or by consuming a media presentation. The video is analyzed to determine eye-blink information on the individual, such as eye-blink rate or eye-blink duration. A mental state of the individual is then inferred based on the eye blink information. The blink-rate information and associated mental states can be used to modify an advertisement, a media presentation, or a digital game.