Designer's Notebook: Positive Feedback
January 4, 2002 Page 2 of 2
So far I've looked at both the benefits and the dangers of positive feedback. The benefit of it is that it prevents stalemates, helping games to come to an end. The danger is that it will unbalance a game too quickly and bring it to an end too soon. So how can we limit positive feedback? There are several ways.
Negative feedback is the opposite of positive feedback; it's an effect that tends to diminish, rather than amplify, the output of a system. A good example of using negative feedback to control positive feedback is the way that the player draft works in American professional football. In general, a team that wins a lot is going to have more money than a team that loses a lot. A winning team could use that money to outbid other teams to hire the best new players graduating from college. The best teams get more money, which enables them to hire the best players, and so they continue to win. Poor teams can only afford poor players, so they continue to lose - a clear case of positive feedback.
In order to prevent this, and try to balance the strength of all the teams, the National Football League introduced a drafting system. New players can't simply auction themselves to the highest bidder; rather, the teams take turns to choose players from those available, and most importantly, the worst teams choose first. This means that the worst teams get first choice of the best players, and the quality of the teams is evened out somewhat. Of course, it's not that simple in practice; teams are allowed to trade their positions in the selection order, and the quality of their play depends a lot on the quality of the coaching, not to mention the other players already on the team. But the principle is sound. The draft system helps to prevent one team from establishing an unassailable position through positive feedback.
Be careful about negative feedback, however - if it's too strong, it can produce stalemates or even wild swings in the lead, as Figure 6 illustrates. In this example, being in the lead confers some kind of strong disadvantage that causes the lead to flip to the other side and back again.
You often see this in turn-based multi-player party games for adults, in
which the object isn't really to reward skill, but to have a good time without
worrying too much about who's winning. Everybody gets to be in the lead
at some point, and the winner is mostly a matter of chance.
Limit the Benefits that Positive Feedback Provides
In chess, it's obviously helpful to remove your opponent's piece from the board. But imagine what chess would be like if you could not merely remove the piece, but turn it into one of your own. This would confer a much greater benefit to taking an opposing piece, in other words, stronger positive feedback. Chess games would be shorter. This actually happens in Japanese chess, which is called shogi. A player who has removed an opposing piece from the board may reintroduce it at a later point as one of his own (with certain restrictions).
This is why most real-time strategy games don't allow you to seize enemy units and use them yourself, nor do they allow you to take over enemy production facilities. If you could grab your opponent's factories and start turning out units for your side, the game wouldn't last very long. They are limiting the benefits that positive feedback provides.
In addition to the drafting process, pro football has other rules that help to prevent the wealthiest teams from dominating all the others year after year. One rule is the salary cap, which limits the total amount that each team may pay all its players. No matter how much money a team has, it can't spend more on salaries than the salary cap dictates. Another is a fixed team size. No team can have more than 53 players during the regular playing season, even if it can afford to. These artificial restrictions serve to constrain the effects of positive feedback. In effect, they're making sure that "money isn't everything."
Define Victory In Other Terms
As I mentioned earlier, the victory condition doesn't have to be defined in terms directly influenced by positive feedback. In chess, victory is defined in strategic rather than numeric terms. In real-time strategy games, you can create missions in which victory must be achieved by stealth, or by detecting a weakness in the enemy defenses, or by surviving for a certain amount of time, or any number of other scenarios. One of the weaknesses of RTS's at the moment is that too many of them depend on overwhelming the enemy with sheer numbers - in effect, production efficiency - rather than rewarding strategic skill. This leads to a "cannon-fodder" mentality among players that is uncomfortably reminiscent of Field Marshal Haig at the Somme. Let's hope they don't practice using those kinds of games at West Point.
Ratchet Up the Difficulty Level to Compensate
This is exactly what role-playing games do. As I described above, there's clear positive feedback in the character growth: winning battles enables you to buy better weapons which enables you to win still more battles. If you always faced the same kinds of opponents, you would quickly become invincible, and the game wouldn't be much of a challenge. Therefore, as your character's strength and ability grows, the game increases the toughness of your enemies as well. The difficulty of winning each battle remains fairly constant (with local variations) throughout the game.
Increase the Influence of Chance
This isn't the best way to reduce the effect of positive feedback, but it does work. Monopoly does this to some extent. One bad roll of the dice can set the leading player back significantly. Of course, it can hurt just as much as it can help, unless you load the dice against the leading player - and if you do that you'd better not tell them about it! Children's games tend to rely on chance more than games for adults do. It helps to balance out disparities in skill and allows the loser to blame bad luck rather than himself (I don't necessarily endorse this, I merely note it).
Balancing a single-player computer game is a bit different from balancing a multiplayer one. In a single-player game it isn't necessary to be "fair" in quite the same way as it is in a multi-player game. The challenge in single-player real-time strategy and role-playing games usually depends more on the player's ignorance of what he's up against than the computer's strategic or managerial skill - often because the computer doesn't have much. But most RTS's are designed with multiplayer modes these days, and in those cases it is necessary to balance them properly and make sure you're being fair to each player, especially if they have asymmetric forces. In multiplayer mode, positive feedback has an important role to play. Use it wisely!
Page 2 of 2