The item I observed during class was the light discrimination apparatus. This apparatus demonstrates the various psychophysical methods used in visual discrimination. The subject is supposed to watch the two 1.375” diameter light stimuli while the examiner adjusts light intensity. The subject’s task is to determine when lights are at an equal intensity or when one light is more or less bright than the other. Each stimulus can be independently varied in intensity by the subject or examiner. Light stimuli are presented using high intensity LED lights, which are set up to give consistent and highly reliable intensity across its usable range.