Gross potential changes in the electrical activity of the brain due to a sensory stimulus such as a flashing light. The location of recording, the type of stimulus, and the state of the subject are reflected in the properties of ERPs, such as the wave shape and the latency (i.e., time delay). With ERPs, researchers ask participants to do the same task over and over again and they average all the EEGs recorded during those repeated trials. The variation due to random firing averages out. ERP has become the favorite tool of neuroscientists studying moment-to-moment consequences of attention in the brain.