A theory of 'inattentional blindness' to clowns & unicycles

I don’t own a cell phone because Vermont service is spotty to non-existent in many parts of the state. This despite Governor Douglas’ much vaunted but yet to be realized E-State Initiative. But I digress. ……anyway I can’t comment from personal experience regarding cell phones.
I would like to think though that I’d notice a clown on a unicycle more often than not even if speaking on a cell phone. One thing that speaks well of this study is that they actually found a way to employ clowns on unicycles in a scientific endeavor.
The study(excerpted here )documented real-world examples of people who were so distracted by their cell phone use that they failed to see the bizarre occurrence of a unicycling clown passing them on the street. The journal, Applied Cognitive Psychology published the results of studying effects of divided attention during walking .They claim to have proven what may be obvious to anyone, namely cell phone use can be distracting. Various types of distractions were tested on individuals walking including MP3 players, talking on cell phone, walking without electronics and walking alone.

In the first study, it was found that cell phone users walked more slowly, changed directions more frequently, and were less likely to acknowledge other people than individuals in the other conditions. In the second study cell phone users were less likely to notice an unusual activity along their walking route (a unicycling clown). Cell phone usage may cause inattentional blindness even during a simple activity that should require few cognitive resources.
Compared with individuals walking alone, in pairs, or listening to their ipod, cell phone users were the group most prone to oblivious behavior: only twenty-five percent of them noticed the unicycling clown. The walkers not using a cell phone noticed the clown over fifty-percent of the time.
Dr Ira E. Hyman, Jr. at Western Washington University, head researcher of the study, says, 'If people experience so much difficulty performing the task of walking when on a cell phone just think of what this means when put into the context of driving safety.