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The Designer's Notebook: Numbers, Emotions, and Behavior
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The Designer's Notebook: Numbers, Emotions, and Behavior

January 27, 2009 Article Start Previous Page 2 of 3 Next

There weren't really characters in Balance of Power, but the actions of your AI opponent sort of felt like the actions of a government, and Crawford enhanced this feeling with the diplomatic language he used to announce their activities. The language could be tougher or more conciliatory depending on how the other side was "feeling."

Crawford created a variable called pugnacity for each side, and another called nastiness which applied to the whole game. Pugnacity started at a slightly random neutral value (higher for the Russians than the Americans; this view is now rather outdated) and got higher or lower as its side engaged in aggressive or conciliatory behavior respectively. The overall nastiness of the game was increased by military activity and crises, and only went down with time.

As Crawford says in the book, "The effect of these two terms is to create a mood to the game. Players who pursue confrontational strategies will increase their own pugnacity and the game's nastiness.

Executed properly, such a ruthless strategy will encourage weak nations to Finlandize to the player. [note: in political parlance, "Finlandize" means to align themselves diplomatically with the player's country, a valuable achievement for the player.] But minor slips can cause the other superpower's pugnacity to increase and your own pugnacity to fall as you find yourself backing down too many times in crises."

If you play the game often enough, you can actually feel this mood. Aggressive actions will cause the other side to become more hostile as well, but showing too little backbone will cause the smaller countries to think you're weak and align themselves with the other side. You can tell when you're not getting any respect.

Pugnacity, diplomatic respect, and geopolitical prestige are emotional concepts that we don't often see in video games, and certainly not in 1985 when Balance of Power first came out.

About five years ago I wrote a column called "What Evil Lurks in the Hearts of NPCs?" In it I talked about making truly three-dimensional characters -- characters that behave inconsistently (and therefore realistically) because they have internal conflicts. For example, instead of characterizing one person's feelings about another with a single numeric attribute that runs from negative (I hate him) to positive (I like him), suppose we create two attributes, one for love and one for hate.

If there were a lot of love and no hate, they would be friends (or more!); if there were a lot of hate and no love, they would be enemies; but there could also be a lot of both, which does occur in certain circumstances. You would then have to craft a behavior system that expresses this internal conflict.

I don't know exactly what's going on inside Façade, Michael Mateas and Andrew Stern's brilliant experimental game about a failing marriage, but the characters definitely have mixed emotions about each other. The Sims, too, turns numbers into human behavior -- though perhaps in a less sophisticated way that Façade did. Façade is about a specific pair of individuals and their friend, the player's character.

The Sims allows the player to create any sort of person she wants, so it has to have a generic model of relationships and behaviors that would work for anyone. But in both cases, these games produce their visible output as human interactions. The player doesn't get any convenient digits or power bars. She's not supposed to be thinking about the game's characters as simulations, but as real people.

Façade uses language, which introduces all sorts of complications -- because a conversation has to flow intelligibly even as the words chosen reflect the speakers' emotional states. The Sims only uses Simlish, but the characters still express their feelings to a degree through the symbols that appear on the screen, and they still have certain decisions to make: do I continue to talk to this person or stop and walk away; do I interact with him or her physically, embracing, kissing, slapping, fighting, and so on.

Such a system is extremely complicated to develop and even more complicated to test, especially if the characters are capable of feeling conflicting emotions. If a character behaves inconsistently, is it a bug or a legitimate expression of his feelings?

I think there's another area where we could improve our emotional simulation and thereby produce richer behavior.

Article Start Previous Page 2 of 3 Next

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