In his latest Dev Watercooler blog post Ghostcrawler talks about how many abilities are optimal for a class to have.

The balance the class design team has to walk is between boring and too difficult and it’s a tough one to keep to I can imagine. My advice to Ghostcrawler here would be to look at George Miller’s famous study to provide guidance here.

I think about class design abilities really as an interaction with a fight/battle/encounter of some kind. During that fight George Miller tells us that everyone should have very little problem holding up to 9 pieces of information in their head throughout the fight.

In every other software development exercise I would say shooting for 9 would be the wrong way to think about it and we should ease the burden on the user. Video games however are different, without a high enough cognitive load our brains would switch to autopilot and we’d soon loose interest (see archaeology). To be successful the design team at Blizzard, in my humble opinion of course, should aim for 9 pieces of information to be successful, 10-11 to be exceptional.

To further complicate things, the interface of the game influences this. Imagine for a moment you played with the interface completely hidden. This is going to be from a warlock’s perspective. I would need to keep track of the remaining duration of all my DoTs on the target, as well as the CDs on any of my rotational abilities. I need to keep track of the status of my longer term situational CDs be they survival or DPS. I need to keep track of what the boss is doing, and I need to keep track of my own situation relative to positioning, what’s going on in the encounter, damage I’m taking, and things such as that.

Clearly there’s way too much information here for you to just keep in your head. Now we do have things like boss emotes and a lot of people use boss mod addons to help them keep track of boss abilities. I place these on the screen so I can easily forget about them and then look them back up as I need to. The default UI will show you buffs and debuffs on yourself and your target, and there’s addons to manage DoT timing so you can forget about that information as well. This is seeming very simple right?

Now we need to keep track of what’s going on in the environment, so we get to watch the action, and that’s the most important part. This is where you can see that you need to move out of the fire. There’s no addons that will help you completely watch the environment. AddOns like Power Auras Classic, or GTFO can help you move out of the bad, but they can’t help you pro-actively position yourself to an optimal location. Let’s presume that information has to stay in your brain.

Because you have to concentrate on the environment, you can’t stare at things like debuffs, buffs, dot timers, boss timers, or the like. So some of that information has to be stored in your brain. Typically I will pull in two boss abilities at a time to keep track of, as well as my next three casts. This means I can move if I need to and do what I have to do on the move when I can’t look down. Now we’re at 6 pieces of information in my little brain.

Here’s where things can get tricky though. As a raid leader I also need to be aware of things like healer mana, available raid cooldowns, and things of that nature. So let’s take 2 off the top right there and we’re at 8 pieces of information for a DPS raid leader to keep track of.

If we say I keep track of 4 abilties, which Ghostcrawler says seems to be optimal, we’ve reached the limits for my brain at 9 things I’m actively tracking.

Ever wonder why you feel drained after a really long boss fight where everything clicks? Blizzard is pushing your brain to the limit.