A novel technique to test brain waves is being used to see how the brain processes external stimuli that do and don't reach our awareness. "When we have different things competing for our attention, we can only be aware of so much of what we see," said a researcher on the study. "For example, when you're driving, you might really be concentrating on obeying traffic signals." But say there's an unexpected event: an emergency vehicle, a pedestrian -- will you actually see the unexpected, or will you be so focused on your initial task that you don't notice?