If you try recollecting past experiences, you will realize that an element of surprise can help you cope with the city stress- traffic, crowd, or simply say hectic repetitive chaos and it need not be scientifically proven.
So can we think of creating everyday surprises - pleasant of course, but can be weird sometimes - along the much traded route of our cities - a suddenly changed striking colored building, pink or florescent or yellow; a sudden surge of artificial wind in a subway, a sudden burst of soft rock music at bus shelter; a glowing bus or a decorated tree and so on, its like taking street performance to the next level which includes whole environment rather than just performer.