Human brains IMHO are merely engines which consume inputs and react to them. Every single action a human being does is influenced by the inputs it has received at some point in the past.. Building initially on instincts, over time, remodeling their behavioral templates to keep them alive, reproduce and increase the chances of certain inputs happening which trigger certain chemical reactions, which ultimately are directed by instinct as a way to stay alive or reproduce.

There is no free will, only the perception of free will. We are just part of an infinitely complicated electrical and chemical reaction.. It's very very complex and therefore impossible for us to understand fully.

.. of course, I could be wrong.. we could always be Magical Souls - driving a human vehicle, just waiting for it to break down enough so it stops and the soul is released again..

Apologies for the apparently cheap poke at religion, not my intention to offend but I think the spiritual side always muddies the water so I wanted to get that out of the way so we can think about this from a pure engineering perspective.

My point about AI and sentience is... It should be possible to fabricate, but very hard to do requiring a massive increase in computing power and perhaps a new shift in computer technology, perhaps by modeling the human brain in a lot more detail.

But, If it's possible to create sentient AI actors, is it ethical to kill them/torture them in a game?
An actor who's been given the ultimate problem solving and learning capabilities, which could be human if they were in a body..
Actors who actually run and are scared by the player holding a machine gun.. who don't want to die..

Perhaps unrealistic at the moment but food for the debate?