Black Bears are smart, they will lay low in the bush and hide till you come out and then charge. They know that if you see them you will not bring food. Normally people just scream, drop the food and run. Of course if you dont drop food, then you are the food.
If black bears are so smart, then how are they caught when they come into suburban/urban areas like Glendale, CA? (See: Glendale Bear, Sleeping In Tree, Tranquilized & Returned To The Wild -- Again)