"If we were writing artificial intelligence for a robot, we would have to write all kinds of computer vision and analysis of the images to figure out what it was seeing. But because [the Halo characters] live in a simulated world, the characters can directly perceive that world. We chose to do that through simulated senses, because that way, the characters perceive the world in a way that players can reason about, because the player understands how their senses work in that world. We made simulated senses [for the AI].
So we have simulated vision, hearing and also a little bit of tactile knowledge. Where the player has five senses to deal with, and they're well developed, the AI in Halo really primarily only responds to visual input and sound input. That's because the two ways the player generally makes himself known to the AI is: The AI sees the player or they make a noise, like shooting someone."