A Psychometric Function is a mathematical equation that plots the performance of a participant on a perceptual task against a physical aspect of a stimulus, such as contrast, size, or intensity. Performance is measured as percentage of correct responses or responses where the participant was able to detect the stimulus. For example, humans cannot hear sounds at very low or high frequencies. A psychometric function can be used to show or predict the point at which a sound can be detected based on its frequency or other parameters.