Think of these concepts like side quests. You don't need any of them to design an rpg. In fact, when you're starting out, you should enter the industry with a blank slate. So, stop right now. Turn around. It's dangerous to go alone. Take the guide to the grid system basics with you. Alright. Ready? Go forth! 

Okay. They're gone. It's time to crack open some books. 

"Design Lore" is my silly way of describing a concept that combines art, science, and theory. (My apologies to the lore orthodox who hate the word being thrown around.) Some of these concepts will seem like cheat codes, others warnings, and some like obvious fact. 

You get to decide how you want to challenge or embrace them.

They're inspiration for games that haven't been invented yet. Rumors to discuss over ale. And more importantly, they're opportunities to discover something new. 

Let's get started.

Aesthetic-Usability Effect

Users subconsciously perceive aesthetically pleasing designs as more usable.

In other words, if your game looks really good, people will tolerate its flaws. The positive response might even lead them to believe it works better than it does.

Lessons to be learned

• Aesthetics can help. Some companies succeed where others fail, even when their game's rules or ideas are less polished. The opposite can also be true. Poor visuals can and will bleed into your game's other qualities. A good game can be hurt by bad visual design. Don't skip on it.
  
  
• Best in show. Are the winners of award shows always the best in their category or are they the best looking in their category? Aesthetic-usability can fool us. That's why it's important for awards to have discussion. Critical discussion can override our subconscious influences.

Further Reading

Apparent Usability vs. Inherent Usability
Masaaki Kurosu, Kaori Kashimura | Hitachi Design Center

Positive Affect and Its Influence on Cognition
F. Gregory Ashby | University of California, Santa Barbara

Universal Principles of Design, Revised and Updated
William Lidwell, Kritinia Holden, Jill Butler | Rockport Publishers

Jakob’s Law

Players will grade your game based on how similar it is to games they’ve played before.

This phenomenon is why players unjustly compare games to one's they've played. Their brain wants to use existing mental models. Your job is to reassemble those familiarities into something new.

Lessons to be learned

• Slaying the dragon. Dungeons & Dragons is the most prominent RPG in the world. If you are interfacing with any of its players, you will be subject to Jakob’s Law. How might you compare it favorably in order to defeat it?
  
  
• Teaching is undoing. The way we teach RPGs has to consider the cognitive bias established by previous games. The more similar your game is to another game, the more "wrong" it may appear to a grizzled player. 

Further Reading

Jakob's Law of Internet User Experience
Jakob Nielson | Nielson Norman Group

The Power Law of Learning
Raluca Budiu | Nielson Norman Group

Parkinson's Law

A task will fill the time you give it, even if additional time is unrelated.

This is more folk wisdom than true psychology. Even worse, its origins are rooted almost exclusively in productivity for commerce. Still, it's a real phenomenon for anyone who works in a project-based format. That includes you, your collaborators, and your audience. Parkinson’s Law is a way to describe why Dungeon Masters spend years making their campaigns, or why designers can tinker with a game for months. Without built-in stops, incentives, and scaffolding, you'll likely fall victim to it. 

Lessons to be learned

• Build in doomsday buttons. How might we insert natural endings into our game designs for combat, narration, or prep? How can we help players do less? My wager: light a fuse. Make combat escalate. Make it impossible to go on forever. Board games have gotten really good at this. 
  
  
• Performance and productivity can be at odds. I know. You're a perfectionist. Your benchmark for success is what makes you the David Fincher of RPGs (oh, geez). Unfortunately, part of Parkinson's Law's allure is the over emphasis on performance rather than just getting it done.

Further Reading

Parkinson's Law on Wikipedia
Assorted Authors | Wikipedia

Time Pressure, Performance, and Productivity
Don A. Moore, Elizabeth R. Tenney | Emerald Group Publishing Limited

The Secret to My Productivity
Hank Green | Vlogbrothers on Youtube

Hick's Law

The more options and complexity there is, the longer and harder it is for players to make a decision.

In design, we alleviate this stress by grouping choices together, emphasizing differences, on-ramping our users to lighten the cognitive load, and by suggesting order of priority. In other words, we give the audience less information to process.

Lessons to be learned

• Simplify the table. Complicated or busy player sheets can pull a player down into the mud on their turn. Busy maps can burn up time when they can't make a decision on where to go. 
  
  
• Install big red buttons. Sometimes you can't reduce any further, but that doesn't mean everything is relevant all at once. When you install a big red button, the other buttons become irrelevant to the Red Button Pushers. Every player has their big red button. Find it.

Further Reading

Hick's Law on Wikipedia
Assorted Authors | Wikipedia

The Choice Overload Effect
Jennifer Clinehens | Choice Hacking on Medium

Hick’s Law: Making the Choice Easier for Users
Mads Soegaard | Interactive Design Foundation

Miller's Law

The average person can only keep 7 (plus or minus 2) things in their working memory.

In games, this number drops off quickly with how complicated and abstract gameplay can be. Help players by organizing content and rules into smaller chunks using design principles and the Gestalt Laws.

Lessons to be learned

• Miller's training wheels. If the player is new to tabletop games, I’d lower this number to 3, plus or minus 2. Tabletop games take practice.
  
  
• Lean on the calculators. Tools for memory can be built into our designs. Things like counters, tokens, and messages on character sheets are ways for the designer to help. It's not that they can't do the work—it's that they shouldn't have to.

The Isolation Effect

When there are multiple objects present, the most different is the most remembered.

Use this effect to your advantage. Design can make a key rule visually distinctive and therefore more likely to be remembered. Find the balance, and you can make a game’s strengths the only thing they remember. (Assuming they don't have too much to remember as it is.)

Lessons to be learned

• Tieflings tieflings everywhere. The most remembered thing will likely become your most used thing. I'm not saying that's what happened with tieflings, but the isolation effect didn't hurt. 
  
  
• Subjectivity is the challenge. Your "most different thing" probably won't be the same for everyone. If you're trying to use the isolation effect to your advantage, you'll have to master making one thing stand out without making everything else boring by comparison. 

Peak-end Rule

People judge an experience based on its climax and ending rather than the entire experience as a whole.

Design for those moments. Identify when your design is most compelling, exciting, and entertaining. If you can make the ending that climax, you'll have a chance to walk away with the winnings.

Lessons to be learned

• Bad endings spoil everything. Don't skimp on the mechanics, components, and pages that'll feature at the end of a session. That's where your game wins the table's hearts.  
• Be critical of the middle parts. Players and readers tend to have fewer opinions about a game's middle, so you have to do the digging. Are those systems fun or was the ending they eventually led to fun? Why not both?

Serial Position Effect

Players tend best to remember the first and last items in a series.

This means, to improve memorization, you should place important information at the beginning or end of your lists and patterns. Less important details should be in the middle where they'll be glossed over or retrieved when reminded.

Lessons to be learned

• Order that list accordingly. When you’re writing for tables or room descriptions, unless the order is telling a story, put your favorite stuff at the beginning and end so players are likely to remember it.
  
  
• Bury the twist in the middle. If you really want to surprise players with a trap, betrayal, or visual flourish—put the hints where their subconscious will work against them. The shadow of a lurking spider? Put it on bullet point two or three. That'll keep them in the dark. 

The Zeigarnik Effect

Players remember incomplete or interrupted tasks better than completed ones.

This applies to what’s happening at your table (character progress, story arcs, etc.) but also applies to your game design (progress markers, additional content, open-ended systems).

Lessons to be learned

• Make what's incomplete visual. If you want players to remember and seek out something, design it so that it will be visually unfinished until they've completed it. A lot of games do this with character sheets. If your game is about acquiring loot, how can you make an empty bag impossible to ignore on a character sheet? What if the progression is relationships?
  
  
• Incorporate completed objects into the action. Players seldom stop to enjoy what they’ve accomplished. All they remember are their weaknesses, unfinished clocks, and rumors. If you want to give them satisfaction, make their completed projects feed into the incomplete ones.

Goal-gradient Effect

The closer your audience gets to completing a task, the faster they’ll work to reach it.

In other words, giving your players and GMs a sense of progress in your game’s design encourages them to read all the way through. Tables of Contents, progress markers, and other visual motifs are great methods for evoking the Goal-Gradient Effect.

Lessons to be learned

• Puts some dials on your books. Books that indicate your visual progress as you turn the pages have a higher completion rate than others. In a dark fantasy game, this can be corruption. In a thriller, it can be increasingly more redacted text. Find a thematic way in. 
  
  
• Keep the runway clear. If something in your design is making your audience go all in, the last thing you want is to hinder them. Don't be afraid to err on the side of simplicity. Let the design fall away. It's done the job.

The Ikea Effect

People value an object more if they assemble or finish it themselves.

Named for the furniture brand of the same name, the IKEA Effect is when people value things they make (or finish) more than things they don’t. If you give them a box to sell, they'll sell it for cheap. If you give them a box to build and sell, they'll sell it for a lot more. 

Lessons to be learned

• Homebrew is a winning stew. Games that encourage homebrew make zealots of their fans. There are other factors at play, but the Ikea effect is real. When they build onto an existing game—even if it was to "fix it"—they're likely to value the original even more.
  
  
• Building characters builds love for the game. The character is the central lens most players experience a game. Character building, therefore, is also game building. If they build even a little bit, and they enjoy building the character, they might value the game more.