In Game Design, affordances are what an element of the game allows the possibility of. Picking up a sword indicates to the player that they should use it to cut something, while placing a door in an environment means that it can be opened to reveal something on the other side.
Emily Schatz, Co-Lead Game Designer at Naughty Dog, currently working on The Last of Us Part II, was the Lead Level Designer on Uncharted 4. She wrote a very interesting article on how Naughty Dog applies the theory of affordances to their Level and Environment Design. She clearly explains this concept and illustrates the psychology behind Game Design.
It's well worth the read as it isn't long, but for the sake of explaining my takeaways, I'll be summarizing the contents.
With the advent of high processing computers creating lifelike experiences, designers have to come up with techniques that tell players what they are able and not able to do. Every element of a game has affordances, which is what interactions they are able to be used for. A ladder is used for climbing vertically, or a door is used to enter or exit a space.
As designers, we want the player to interact with the game in the way it was designed to, so we have to clearly communicate the affordances that every game element has and doesn't have. To do this in Level Design, an Environmental Language is developed, where the most important affordances to do this with are Cultural and Inferred Affordances.
Cultural Affordances are the affordances that players expect based on what they know from outside of the game. These are usually assumptions, such as gasoline cans should explode when shot at, or fire hurts when walked into. Cultural Affordances are powerful, but can be misinterpreted based on the person.
Cultural Affordances can also take the form of shape association, where certain shapes and silhouettes convey different meanings. Round shapes indicate safety, square shapes solidity, and triangular shapes danger.
Inferred Affordances are the logical deductions a player makes based on the game world and systems. Metrics are a good example of this, as when a player sees an opening that is a certain height, they know to crouch in order to go into it.
In order to ensure the correct interpretation of affordances, they must be isolated. The amount of isolation depends on how critical the mechanic associated by the affordance is. For example, the Inferred Affordance of horizontal handholds while climbing in Uncharted is so crucial, that any rocky surface must be devoid of any horizontal texturing so that the only horizontal element are the handholds.
Another form of isolation is through buffering metrics. For example, Uncharted 4 has cover that Nathan Drake can use to avoid gunfire. By making sure that the height of all cover falls within a relatively small range, the player can instantly know through association what they can and can't hide behind.
I omitted what I felt was appropriate from the article, but I do heavily recommend giving it a read.
This article provides many takeaways that myself and many others should keep in mind. Key points that had stuck with me since I first read it was;
The notion that a break in immersion occurs when a "player’s desire to act is unsupported". Naturally, Game Designers can't support every possible desire to act, so rather we must guide the player to desire what the game can support.
Metric-wise, it is important to have a "dead zone" that ensures that affordances are never unclear. For example, if the player can only walk on slopes 35 degrees or less, then a dead zone should be implemented so that no surface in the game can be greater than 30 degrees and less than 40. By omitting this range of surface angles, there is a clear separation between what the player can walk on and what they can't. This eliminates any kind grey area between walkable and unwalkable, since there is a bigger gap between the types of surface.
Denying affordances is also a large task. Making players see something as unactionable is important to keep the them on track, as they naturally push the limits. Denying affordance isn't the same as not supporting it. Immersion is broken when expectation doesn't meet reality, so rely on keeping expectations where you want them.
Cultural Affordances are powerful and useful, but make sure to research the implications beforehand. Depending on culture, some things may differ. The colour, red, for example, has connotations of passion, and danger in North America, while East-Asian cultures view it as imagery associated with good fortune, happiness, and love.
Overall, this article has many explicit takeaways for Level Designers and Environment Artists, and many more abstract ones for designers of other sorts. This goes to show the amount of thinking that goes into designing a fully engaging player experience and the amount of psychology that is behind the whole process.