I was reading Programming Game AI by Example and found the following paragraphs really interesting, even though they don’t really apply to Shadow of a Soul.
But what is this mysterious thing we call artificial intelligence? With regard to game AI I am firmly of the opinion that if the player believes the agent he’s playing against is intelligent, then it is intelligent. It’s that simple. Our goal is to design agents that provide the illusion of intelligence, nothing more.
Because the illusion of intelligence is subjective, sometimes this takes very little effort at all. The designers of the AI for Halo, for instance, discovered their playtesters could be fooled into thinking the AI agents were more intelligent simply by increasing the number of hit points required to kill them. For one test session they allowed the agents to die really easily (low hit points); the result was that 36 percent of the testers thought the AI was too easy and 8 percent thought the AI were very intelligent. For the next test session the agents were made harder to kill (higher hit points). After just this small change 0 percent of the testers thought the AI was too easy and 43 percent thought the AI was very intelligent! This is an astonishing result and clearly shows the importance of playtesting throughout the game development cycle.