Sensitivity is the strength of the capacity to detect and discriminate stimuli. It is how strong the perception of a stimulus is in an individual. A person who has higher sensitivity will perceive a stimulus more strongly at a lower level than someone who is less sensitive to the stimulus. If two people are looking at a light that is increasing in brightness the one who is more sensitive will squint and close their eye sooner than the person who is less sensitive. People have variations in sensitivities to different stimuli. For example, research has shown that redheads are more sensitive to pain than individuals with other hair colors.