Although our eyes may see more, the human brain can only pay attention to three moving objects at any given instant, says a new study. The discovery by an international team has important implications for road design and safety, driver and pilot training, fast-moving sports and other areas of human visual activity affecting safety and performance. For the study, the scientists tested the brain's ability to detect signal directions using random-dot stimuli which consisted of a field of scattered dots, with groups of intermingled dots moving in different directions.