Alexander and Cowey investigated how contrasting brightness of stimuli affects blindsight patients' ability to discern movement. Prior studies have already shown that blindsight patients are able to detect motion even though they claim they do not see any visual percepts in their blind fields. The subjects of the study were two patients who suffered from hemianopsia—blindness in more than half of their visual field. Both of the subjects had displayed the ability to accurately determine the presence of visual stimuli in their blind hemifields without acknowledging an actual visual percept previously.