Feedback in systems design, and a need for new terminology

by Darius Kazemi on January 24, 2012

in design

About a year ago on a thread on Google Buzz (RIP) I wrote a quick definition of  ”positive feedback” and “negative feedback” in terms of their technical, systems design meaning. I figured I would repost it here, since every now and then someone asks me what it is and I search my email to copy/paste it. It’s pretty slapdash but it gets the point across, and people have found it useful. So… here you go, internet.

In short: negative feedback is a system that regulates itself. Think of a thermostat. You set it to a certain temperature T. If the house goes above T, it instructs the systems to cool the house. If the house goes below T, it instructs systems to heat the house.

Positive feedback is where things are reinforced and amplified. Imagine a thermostat that cranks the house hotter when the temperature is above T, and makes it cooler when it’s below T.

The main difference is that in the first example, the temperature will tend to remain at T. In the second example, it is highly unlikely the temperature will be T, and in fact it will trend towards either very hot or very cold.

The simplest example of negative versus positive feedback in game design that I can think of is possession rules in 1-on-1 pickup basketball. A negative feedback rule is something like, “If I score a basket, you get to start with the ball.” By giving an advantage to the loser, you’re evening the playing field a bit and bringing the temperature back down to T, so to speak. A positive feedback rule would be, “Winner keeps the ball.” This means winners tend to keep winning, making the house hotter and hotter.

Randy Smith likes to use Mario Kart as an example of a game with strong negative feedback: items like the Blue Shell cause people in the winning position to be at a disadvantage so those behind can catch up. This is also colloquially known as a “rubber banding” mechanic.

Mainly this is in stark contrast to the other way the terms “positive feedback” and “negative feedback” are used in game design: to signify something positive given to the player (reward) or something negative given to the player (punishment). “Feedback” in general can refer to either feedback loops like I describe, or to the general concept of “giving information to the player about the results of their actions.” I would vastly prefer if we started disambiguating the two usages. I’d like “feedback” to retain the meaning I sketch above, which is probably due to my bias as someone trained as an electrical engineer!

Any suggestions out there for a word other than “feedback” that would describe “giving information to the player about the results of their actions”? Or, hell, a different word for “systems whose outputs determine their future inputs” (which is what I describe in my examples above)?

(Edit: “reinforcement” has been variously suggested here and on Twitter for EITHER kind of feedback. See my comment below on why I think it’s only suitable for the “giving information” kind.)


Sean Beanland January 24, 2012 at 11:26 am

I’d suggest that “enforcement” or “reinforcement” would be better words for what you described, as I think “feedback” has too much traction when it comes to describing how you inform the player. I don’t think that term will go away.

Darius Kazemi January 24, 2012 at 11:29 am

Actually I think the opposite — “reinforcement” is a great candidate for the “giving information to the player” thing, because it implies a human intelligence and scolding/praise. It makes no sense for what I describe! (I’m in an idealistic mood today and more interested in what’s technically right than what people are likely to adopt.)

Sean Beanland January 24, 2012 at 11:33 am

If we’re being idealistic, then I agree with that interpretation!

Tim Koch-Grunberg January 24, 2012 at 11:35 am

“Feedback” in the sense of information given to the player is “player agency made visible”. Players act, the system reacts, and shows the outcome to the player. The problem lies in finding a suitable word to describe this. “Feedback” sort of stuck, and it just sounds pretty good.

What about “Response”?

Olly January 24, 2012 at 11:51 am

would feedback serve for both but when referring to your systemic feedback could you use a prefix of some kind? containment feedback (negative) and escalation feedback (positive)? Just a thought.

Jason January 24, 2012 at 12:57 pm

Thanks for this introducing this interesting question. It strikes me that something like ‘render’ would satisfy for “giving information to the player about the results of their actions,” precisely because there’s no inherent balancing effect implied: it’s simply output. The player does x, the system simulates environment with that data in mind, renders world (through text, video, audio, and/or haptics) for player–classic game loop.

Within that simulation step, however, is where the current game state is checked against the rules (is the temperature too high, too low?), applies balance mechanics (blue shell now available to player 7, who is in last place), all of which leaves ‘feedback’ available for the intent you describe above (and fits, I think the first two definitions in the link that Ralph Koster provided on twitter, more so than the last 3 he highlighted).

I’d note that while the blue shell seems a great example of negative feedback as you describe, it isn’t because someone is in first place, but rather it becomes *available* because someone is a certain distance behind. It’s not a direct punishment of the leading player, but rather a balancing negative feedback provided to the losing player, which seems somewhat counterintuitive. Using your definition, it’s technically appropriately ‘negative’ feedback because the losing racer is cold, and the system kicks the heat on. But colloquially it’s not negative because it potentially helps the losing player (which is a reward). As a counterexample: automatically throttling the speed of the leader player would be a negative feedback (and a penalty) for the lead player. In a sense, the blue shell is a great example of the linguistic tension you’re encountering, and why it’s tricky: implementing negative feedback in this case also serves as a reward for the (currently losing) player, whereas throttling is an example of negative feedback that serves as a penalty/punishment.

The *use* of the blue shell, on the other hand, is a traditional ousting/paralyzing move for many kinds of race games (cf Parlett) which represents interaction between players and arguably isn’t ‘feedback’ at all, but simply a ‘move.’

Sparky Clarkson January 24, 2012 at 1:01 pm

The way you’re using “feedback” here mirrors the way we use it in biochemistry to describe, for instance, the regulation of metabolic pathways. So in that sense I don’t see any problem with what you’re writing, but of course once you start talking in a space where many fields are converging, then terminology can get confused. As such, I agree with the way you want to use ‘reinforcement’, but it is difficult to win a fight against a colloquialism.

Perhaps the discussion could be served by talking about the ends rather than the means. Negative feedback serves to stabilize or converge systems that have been perturbed, or to maintain them in a steady-state or equilibrium condition. Positive feedback encourages divergence, amplification of differences, and system instability. Using stability or equilibrium to talk about this will run us up against colloquialism again, because players perceive individual histories rather than averages. “Convergence” and “divergence” mechanics, or “amplifiers” and “dampers” might be useful ways to talk about mechanics or sets of mechanics that act in the way you describe.

Amanda January 24, 2012 at 1:03 pm

I don’t know if you’ve already read this article, but Sirlin calls the engineering feedbacks “slippery slope” and “perpetual comeback”

I remember teaching out of a game design textbook that actually had these definitions backwards in the text. That made it extra confusing when I tried to disambiguate to the students that “positive feedback” in the engineering sense doesn’t mean always “a good thing.”

Zach Kamsler January 24, 2012 at 4:27 pm

I also tend to favor the more formal definition of positive and negative feedback. I also have a soft spot for control theory and system dynamics, and they are also used in this sense by a number of the sciences.

I don’t have a problem with the unqualified use of “feedback” in the colloquial sense, since information given to the player is also feedback in the technical sense (although its effect can be a change in player behavior rather than something intrinsic to the system and much thus less predictable). There can also be some overlap in usage. A reward can be construed as positive feedback if it allows the player to more easily get future rewards. A punishment may also be positive feedback (in the negative direction) if one ignores any impact on player behavior.

Eric January 24, 2012 at 10:21 pm

Feedback seems like a good term.

When I hear reinforcement I think of classical conditioning, where reinforcement is a specific term for something you do to increase the frequency of the desired response. It’s the opposite of punishment and can be negative or positive, which aren’t exactly what you’d think they are (and can get confusing.)

I think feedback more as something that can be desirable (monitor speakers that allow the band to hear itself) or undesirable (a signal being reflected back into a radio and causing interference.) Both of these examples are a response to something that affects the following output.

Philip Morey March 15, 2012 at 12:58 am

Interestingly enough… there is a really obvious word to use for ‘to give information to a player’. Perhaps we could use the word “Inform”? After all, that is the definition.

I do live sound as a hobby, so I really hate getting feedback! ;)

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