There is no excuse for basing a screenplay on taking seriously a well known urban myth and writing it as if the audience believes the myth.
Did no one up the entire production line step out and call bullshit on the discredited 'we only use 10% of our brain,' idea? I am so embarrassed by seeing actors I admire, Scarlett Johansson and Morgan Freeman, deliver solid performances on the basis of an idea at which most people laugh.