When your brain reaches this threshold, it automatically discards the additional information, which is why we can sometimes miss obvious things like an announcement at the airport when we are stressed and trying to control the children, or the no entry signs at the entrance to a one-way street when we are late for a meeting in an unfamiliar part of town.
In a recent piece of research into the distracting effects of mobile phones, researchers at the Western Washington University observed hundreds of people as they walked across the university campus.
To make the research more interesting, they employed a clown complete with red nose, purple shirt and oversized shoes to ride around the campus on a unicycle. Not only did two-thirds of the people using mobile phones fail to notice the clown, they found that the phone-users tended to meander rather then walk in straight lines.
Psychologists call this phenomenon "inattentional blindness" and it is something magicians and illusionists use extensively in their acts. Click here to see an example on YouTube where the illusionist Derren Brown stops people in the street to ask for directions. While they are talking to him a person carrying a large painting passes between them, at which point the person asking for directions is switched. In the original experiment, roughly half of the people failed to notice that the person asking for directions had changed.
Makes you wonder what you might have missed today!