Let's say I have 4 robots and a maze. The only choices the robots are able to make in the maze is to go left, right, forward, or back. 
The first robot has a program it will follow. The program is complicated enough that an observer would have a hard time figuring out the decision tree. 
The second robot will base its choices off of the random particle decay of a chunk of radioactive material inside the robot. 
The third operates with both. It follows a program, but the program is influenced by the particle decay. 
The fourth is a black box, with no way of knowing what is inside the robot or what factors influence the path the robot takes. 
These four robots are released into the maze without any markings showing which is which. After watching them operate for a certain amount of time, do you think you could reliably tell which robot is which?