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Believable Stupidity In Game AI

Posted by Soulskill on from the much-more-common-in-real-players dept.

Gamasutra is running a feature written by Mick West, co-founder of Neversoft, about creating game AI that is dumb enough to defeat, yet intelligent enough that its "mistakes" are similar to those a real player would make, thus preserving the illusion that the AI is not just throwing the game. "The simplest way to introduce stupidity into AI is to reduce the amount of computation that it's allowed to perform. Chess AI generally performs billions of calculations when deciding what move to make. ... The problem with this approach is that it decreases the realism of the AI player. When you reduce the amount of computation, the AI will begin to make incredibly stupid mistakes — mistakes that are so stupid, no human would ever make them. The artificial nature of the game will then become apparent, which destroys the illusion of playing against a real opponent. ... By reducing the amount of computation, we create an AI opponent that is trying to win, but has been crippled in a way that leads to unrealistic gameplay."

3 of 378 comments (clear)

  1. Stupidity is a component of intelligent behavior. by hey! · · Score: 5, Insightful

    And vice versa.

    One thing that is stupid: trying the same things that failed in the past.

    This is a component of smart behaviors as well. If you don't know what to do, try something and watch very carefully how it fails. If you are in a desperate situation and you are going to definitely fail through inaction, then try an action which failed in the past and hope you get lucky. Or vice versa, when the action that usually works looks like its going to fail, try doing nothing.

    Animals freezing in the face of danger is an example of this. It's not much of a defense, but you might get lucky. Maybe the prey a couple animals down the line will get itchy and draw the predator's attention.

    On the other hand, smart behavior can be a component of stupidity. If the red button gets you a treat 80% of the time and the green one gets you a treat 20% of the time, the intelligently stupid thing is to push the red button 100% of the time. The stupidly intelligent thing is to try to work out the pattern of red/green rewards.

    If you want realistic model of stupidity, provide the NPCs with a range of decision making strategies, all of which work to some degree, but the better of which take more effort (computation). The NPC can choose between the strategies with a random function weighted towards the better strategies, but as time and "stress" come into play the function can shift towards the easy but less effective strategies.

    That's a pretty good model of human performance "choking".

    Evolution did not produce human stupidity because it was useless, after all.

    --
    Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
  2. Here's what I'd like by vadim_t · · Score: 5, Insightful

    A computer that plays on equal terms.

    AIs often win in some games not by the virtue of being smarter, but by having an unfair advantage. Examples:

    • In RTSes, constant money injections. This pretty much nullifies attempts to attack resource collection -- they don't need it anyway.
    • Knowledge of the position of everything. In RTSes, they don't need to discover your position. It's useless to try to build an outpost and hide the real base somewhere behind it. In FPSes they know where you are, and can tell when you're sneaking from behind
    • Instant reaction time and all-encompassing awareness. In RTSes, the AI is capable of controlling every unit at once, and knows what's going on in the whole map at once. Meanwhile, the players are limited in the speed they can give orders, and only has a view of part of the world. Due to this, the AI can't be fooled by multiple attacks from different places, it will see all of them perfectly.

    My suggestion: An AI should be coded as a bot, within the constraints given to the player. If the player can only see a part of the battlefield (like in Starcraft) then the AI should have the same limit and need adjust its own viewport to gain awareness of an area. It should also be limited by the fog of war, and lack the ability to see out of the back of its head. To put in another way, a fair Starcraft AI would be one implemented with a camera pointed at the screen, controlling only the keyboard and mouse inputs.

    The idea is that I want to be beaten because the AI is indeed smarter, not because it's got a superior access to the battlefield I can never gain.

    Chess probably comes closest to the sort of thing I want -- the AI and human are fighting on very equal terms. I don't see the calculating millions of positions a second as a problem, that's simply an implementation detail.

  3. Re:Money by fooslacker · · Score: 5, Insightful

    Why is this debasement? Playing against a machine even in unfair settings is still a challenge. The goal isn't to pick only fights you can win but to test yourself and do something new and experience something new.

    As for it being "unfair" it wasn't touted as fair it was a computer v grandmaster experiment not a ranking test.

    The only shady part in my opinion is the refusal for a rematch. If the man is willing to play on uneven ground and give his time (even if paid) to your stunt then you should have the courtesy to let him challenge/redeem himself.