Working Memory in MMO's

Put simply, Miller's Law states that the number of objects an average person can hold in working memory is about seven, plus or minus two. For clarity's sake "short-term memory" is for holding, but not manipulating, a small amount of information in mind in an active, readily available state for a short period of time. "Working memory," however, is a cognitive system with a limited capacity that is responsible for the brief holding, processing, and manipulation of information. The two are sometimes used interchangeably but the key distinction here is that working memory is the buffer that allows you manipulate information held, while short term does not. In essence, working memory takes on a more active role.  Now that the psychology lesson is out of the way, let's dive into how this can be and has been applied to design. 

In The Elder Scrolls Online (ESO), a great amount of care has been taken to limit what the player needs to know to be and feel effective. Quite a bit of this has been accomplished by limiting player choice in a meaningful way as well as nesting information. Let's start with the quintessential element of MMO's, character builds. 

Before going to deep into this, I feel like I need to cover the concept of "Orthogonal Unit Differentiation" coined by Harvey Smith. Harvey explained that this is where units (enemies, resources, etc.) in the game are measurably different in such a way as to force or encourage players to consider and alter their strategies based on the current information at hand or predictable information to come. In ESO, this is applied not only to enemy types but also to the combat system itself. One could argue this is actually "Orthogonal System Differentiation," however, I'll save that discussion of semantics for another time.

Now, for the meat of the topic. Each character class has access to access to 8 categories of skill trees. Of those, the Weapon Category has the largest number of individual skill trees coming in at six, one for each weapon type. Given that players can only equip up to two different weapon types, this really becomes two in most players' minds as they'll likely ignore the unused skill trees. They've also cleverly organized each of these trees with a descending order of priority. The ultimate is listed at the top of the trees that contain one, followed by up to 5 active abilities of the trees that contain those, followed by up to 6 passive abilities. Lastly, players have access to two bars, each having 6 ability slots, 5 active and 1 ultimate.

By organizing the skill trees the way they have in ESO, it helps players organize their thoughts. There are only a handful of ultimates for players to consider when making their build. These ultimate abilities need to have their corresponding resource built up over time before they can be used. This means the abilities available to players fluctuates between 5 and 6. 

The choice to nest all the abilities, skills, etc. in subtrees either accidentally or intentionally helps the accessibility of ESO. Bethseda has a huge following and a rabid fanbase that loves The Elder Scrolls franchise; however, it could be argued that actively considering Miller's Law early in development will help to ensure the long-term health of a complex game from launch. 

How can this be used to make content engaging? Make the conscious choice to never exceed the number of items a player can hold in working memory. With this in mind keep only a handful of those items at the forefront of gameplay at a time and alter which of those items are present at a time.