Maximum Cooldown Time: 6-12 seconds
Purple hippos. Green puppies. Red monkeys. Short term memory is an interesting thing. Yellow birds. Blue horses. It can only hold around seven items (give or take a few, depending on your level of concentration.) Which means for some of you “Orange lizards” is going to drive the first animal right out of your working memory. This is why most game controllers have around seven buttons — White spiders, Pink fish — and most successful action games don’t even use that many. Player’s simply can’t hold all those options in their heads at the same time.
Orange elephants.
But the most important aspect of short term memory isn’t how many options player’s can remember, but how long it takes for them to fade. Or how short. Neurological research indicates that we start to forget details as few as 6 seconds after being introduced to them. After 300 seconds we are only half as likely to remember a concept, and after 10 long minutes… forget about it. (Sorry.) So that means, depending on your reading speed, you’ve almost certainly forgot the first animal by now.
This has a direct application in determining the length of cooldowns for abilities in action games. (In this context, a “cooldown” is the amount of time that must elapse after an ability is used before it can be used again.) The player stores the fact that an ability was used in their short term memory, and if the cooldown doesn’t expire before they forget about it, they may never use it again! It sounds preposterous, but how many times have you seen someone go through a tutorial on how to use an ability, use it successfully once or twice and appear to understand how it works, and then get utterly baffled when required to use it again just a few minutes later? How many times has that happened to you when playing an unfamiliar game? I know it has happened to me more times than I can remember. (Sorry again.)
So, if a cooldown prevents a player from using an ability for more than 6 seconds, there is a risk that they will stop using it entirely. An onscreen indicator that a cooldown has expired helps, but habituation and change blindness limit how effective an indicator can be, especially when it changes very rarely. Repetition helps, because it transfers knowledge of the ability into more permanent memory, but even this is tricky because with a long cooldown what the player will be committing to memory is the fact that the ability is unavailable, making them even less likely to use it. The options, then, are to use very short cooldowns — between 6 and 12 seconds — or rely on a very noticeable reminder when ability is available again.
Indicators have their own problems
For an action game, where onscreen indicators are not desirable, long cooldowns lead to mechanics that are often ignored and quickly forgotten. Maroon walrus.
Rewarding Play 
Has anyone seen examples of cooldowns that increase with each use? I can’t think of any, but it could be interesting. This was a Skinner psychological trick to get you habituated to use, but then make it harder and harder to achieve, iirc.
Nice post.
Just to add a bit to this, simple repetition isn’t the best way to get things to move into long term memory either, rather repetition is best at keeping things in working memory. For encoding to long term memory elaboration is much more effective, in that if a mechanic is closely related to existing knowledge or the player is encouraged to think deeply about the mechanic (understand it in other words) then it will be remembered. This can be done via good introductory uses of the ability in situations that build on a players knowledge or that are particularly novel and stand out.
All that said, all that will do is allow the person to remember that such an ability exists, and if you wanted to get them to remember the cool down period then coming up with a way to elaborate or make the cool down period meaningful might be more difficult (visual indicators leap to mind, say the way the plasma gun in Marathon/Halo visually smokes and such when it is on cool down, but you can only go so far with these).
I think that this has actually worked out for MOBAs, because checking your cooldowns is vital for success. Every time you look down at your ultimate or summoner spell (I played a lot of LoL) cooldown, you are reminding yourself of those abilities. This allows you to more quickly familiarize yourself with new characters without switching into a whole other mode of concentration.
What is maybe most interesting, though, is that this can lead people to rediscover abilities later on. If the player winds up in a situation where they HAVE to use a longer cooldown ability that they have been ignoring, it’s almost like getting a new mechanic out of the game. Given the way that modern progression systems work, that ability will probably be much more obviously viable later on in the game than it was when it was first introduced.
@Ben Good point about relating a concept to other ones the player knows, or even using in-game connections to cement the player’s memory of an ability. “Oh, there’s a locked door, I suddenly recall my lockpick ability is off cooldown!” Although that kind of soft connection is never as obvious to the player as it seems like it ought to be. 8)
I don’t think that this rule is so strong when you only have 4 primary buttons such as in a moba. If it is a secondary button with a long cooldown such as one of your clickable items then this rule may apply once again.
…because moba are well known for being noob-friendly and easy to learn? 8)
Short term memories _do_ last a lot longer when there are fewer distractions. The moment-to-moment gameplay of a shooter or other action game do leave less brain bandwidth (brainwidth?) for cooldowns than your average dota-like, for sure. And most mobas have large onscreen indicators, too.
Would you say this relates to equipment in Halo 3 and the frequency in which players used it (or rather, didn’t)?
I would think that the Halo 3 equipment could have had a problem with remembering that you have, and then remembering to use it in the situation where it was appropriate.
I would also guess that it might be hit by “consumable item syndrome” (to get some D&D nerd in here). In that it is possible that equipment was possibly viewed as a scarce and rare resource and you want to save it for exactly that right moment where you want to use it. That might be my own biases showing there though.
Halo 3 equipment had several issues that made it easy to forget. I think the fact that it wasn’t always available was a bigger factor than the cooldown, but it certainly didn’t help. I think the Arbiter’s stealth camo from Halo 2 and some of the Armor Abilities from Reach are better examples of cooldowns that are too long for short-term memory.
I’ve seen how this tends to happen not just with cool downs, but actual game mechanics themselves. Halo 3s equipment, while sometimes useful, was something I rarely used just because I’d forgotten I’d ever picked it up, or died before being able to use it, or not having it when I thought I did among other things. Armor Abilities as they appear in Reach did easily remedy that problem, for the most part.
As far as mechanics, I went through the first playthrough of reach and a long period of time in Reach not using armor abilities at all either, partly because there wasn’t much time where I was ever required to use it, and no real reason to understand how they worked. Then, I jumped into multiplayer, and really started to use the Jetpack. In a multiplayer environment, I personally tend to pick up on new things quickly, given the need to adapt to win. At the time. That need to adapt and learn lead to me learning and understanding how the various different armor abilities worked, and thus me remembering I had them, the cooldowns, and all of that other relevant information.
I feel like one of Reach’s shortcomings was the lack of motivation to learn how to really use these abilities within it’s main story, or elaborating on them at all within it as a mechanic. A game that, in my amateur opinion, demonstrated and taught mechanics extremely well was the original Portal. Teach concept. Repeat in application at least twice, if not more, then apply to various puzzles as a regular mechanic.