The Bartle Test of Gamer Psychology is a series of questions and an accompanying scoring formula that classifies players of multiplayer online games (including MUDs and MMORPGs) into categories based on their gaming preferences. The test is based on a 1996 paper by Richard Bartle and was created in 1999–2000 by Erwin Andreasen and Brandon Downey. Although the test has met with some criticism for the dichotomous nature of its question-asking method, the test has been taken by a large number of computer game players. As of October 2011, the test had been taken over 700,000 times.
The result of the Bartle Test is the "Bartle Quotient", which is calculated based on the answers to a series of 30 random questions in the test, and totals 200% across all categories, with no single category exceeding 100%. For example, a person may score "100% Killer, 50% Socializer, 40% Achiever, 10% Explorer," which indicates a player who prefers fighting other players relative to any other area of interest. Scores are typically abbreviated by the first letter of each category, in order of the quotient. In the previous example, this result would be described as a "KSAE" result.
Character theory 
The Bartle Test is based on a character theory. This character theory consists of four characters — Achievers, Explorers, Socializers, and Killers. These are imagined according to a quadrant model where the X axis represents preference for interacting with other players vs. exploring the world and the Y axis represents preference for interaction vs. unilateral action.
Also known as "Diamonds," these are players who prefer to gain "points," levels, equipment and other concrete measurements of succeeding in a game. They will go to great lengths to achieve rewards that confer them little or no gameplay benefit simply for the prestige of having it.
Single-player appeal to the Achiever 
Every game that can be "beaten" in some way caters to the Achiever play style by giving them something to accomplish. Games that offer special movies, extra endings, or other bonuses for beating it with a 100% completion rating appeal to Achievers.
Multi-player appeal to the Achiever 
One of the appeals of online gaming to the Achiever is that he or she has the opportunity to show off their skill and hold elite status to others. They value (or despise) the competition from other Achievers, and look to the Socializers to give them praise. As they achieve more, they are no longer easy targets of the Killers and may enjoy their new position on the food chain. These gamers also tend to like seeing their user names at the top of scoreboards and ladder systems. Many games cater to these players by offering special titles and a special exclusive mounts to those that place in the top of the competitive Arena ladder. Microsoft's Xbox Live utilizes the Gamerscore to reward Achievers, who can get points by completing difficult "Achievements" in the various games they purchase. They can, in turn, compare themselves to other gamers from around the world.
In many ways, the Achiever is the style of play most targeted by the MMORPG genre. In many successful MMOs, there is always something else to achieve; even when the character has reached the highest level, there are usually rare items to obtain and objectives that were bypassed the first time around. Since Achievers can sometimes set very obscure goals for themselves, especially if they feel like they'll be (among) the first to achieve them, they may spend long periods of time engaging in a repetitive action in order to get one more award.
Explorers, dubbed "Spades" for their tendency to dig around, are players who prefer discovering areas, creating maps and learning about hidden places. They often feel restricted when a game expects them to move on within a certain time, as that does not allow them to look around at their own pace. They find great joy in discovering an unknown glitch or a hidden easter egg.
Single-player appeal to the Explorer 
Combat and gaining levels or points is secondary to the Explorer, so they traditionally flock to games such as Myst and its four sequels. In these games, you find yourself in a strange place, and the objective is to find your way out by paying close attention to detail and solving puzzles. The Explorer will often enrich themselves in any back story or lore they can find about the people and places in-game. Whereas an Achiever may forget about previous games as soon as they've conquered them, the Explorer will retain rich memories about what they experienced about their adventures.
Contrary to what some may expect, Explorers can enjoy restrictive games as well as permissive ones. The challenge in such a game is to get it to do something its programmers probably didn't intend for it to do; gamers who share a high Explorer percentage with a high Achiever one will often be the ones who set unusual objectives for themselves (like completing the game within a certain amount of time, under certain restrictions, or in a certain order) to put the tricks they've gathered to use.
Multi-player appeal to the Explorer 
The Explorer benefits much the same way as the Achiever does in the massively multi-player environment, as they are surrounded by people who will benefit from their wisdom. They often meet other Explorers and can swap experiences, and most often, Socializers do not mind listening either. Interaction with Killers is usually (though not always) negative, as hostile Killers would interfere with exploration. Most mainstream MMORPGs offer Explorers plenty of lore and rich characters to delve into. However, Explorers will often quickly become bored with any particular MMORPG when they feel it has become a chore to play, with only more of the same ahead. This is of course true to some extent of all gamers, but Explorers can be notoriously fickle, abandoning a popular game within mere weeks while spending months or years delving deeply into a less-popular one.
There are a multitude of gamers who choose to play games for the social aspect, rather than the actual game itself. These players are known as Socializers or "Hearts." They gain the most enjoyment from a game by interacting with other players, and on some occasions, computer-controlled characters with personality. The game is merely a tool they use to meet others in-game or outside of it.
Single-player appeal to the Socializer 
Since their objective is not so much to win or explore as it is to be social, there are few games that the Socializer enjoy based on their merits. Instead, they play some of the more popular games so that they can use their experience to socialize with others who have played them, or use the multi-player features. However, there are some games designed with their play style in mind. (The increasing number of games that offer significant relationships includes the Fable, Mass Effect, and Knights of the Old Republic titles.)
Multi-player appeal to the Socializer 
The online environment is very appealing to the Socializer, as it provides near limitless potential for new relationships. Socializers start filling up their friend lists as soon as they start meeting people, and get to know them better through private messages and sometimes even voice chat. They take full advantage of the ability to join guilds or kinships in many online games, and form fast friendships and try to help other people out. They are compatible with just about everyone; even Killers will often get along with the more respectable Socializers (or simply know better than to pick a fight that the Socializer's friends will get involved in), and the more dramatic Socializers thrive symbiotically on the chaos created by some Killers. Eventually, they will most likely be a well-known name on their particular server, either for the services they provide, or for the drama they are involved in.
"Clubs" is a very accurate moniker for what the Killer likes to do. They thrive on competition with other players, and prefer fighting them to scripted computer-controlled opponents.
Single-player appeal to the Killer 
These gamers love to sow destruction, so games that are high in carnage, action, and destructible environments are definitely a plus. Many of these gamers also enjoy the opportunity to depart from the norm of being "the good guy" who comes to save the day. Instead, they will play on the side of evil or conquest. On the flip side, Killers also represent the archetype which is most interested in affecting their environment, so sandbox games in which they can take a direct hand in building (or destroying) a virtual society will appeal to them as well.
Multi-player appeal to the Killer 
Causing mayhem among computer-controlled people and things may be fun to the Killer, but nothing amounts to the joy of pitting one's skills against an actual player-controlled opponent. For most, the joy of being a Killer results from a friendly competitive spirit. They're in it for the sport, trying to read their opponent's moves and generally acting with honor.
For others, it's more about power and the ability to hurt others or the thrill of the hunt. One such example is "ganking" or "owning", a process where the Killer takes their strong character to a place where inexperienced or weaker characters reside, and proceeds to kill them repeatedly. Once a killer finds a weaker character it becomes increasingly enjoyable to "Hunt" this character, stalking him through different zones. Repeatedly stalking and killing a weaker player adds a thrill of a certain type well described in the novel "The Most Dangerous Game". Once stronger enemy players arrive to help, the Killer either waits patiently or stealthily sneaks somewhere else to repeat the process. These Killers love to have the notoriety of being someone that should be watched out for, or even better, someone to be "Killed on Sight."
In other contexts, Killers are also active in the social and economic sides of a multiplayer game. Market control appeals strongly to Killers, many of whom have a natural talent for reading markets (likely an extension of their common aptitude for sizing up strengths and weaknesses, vital to their play style). Social Killers tend to be guild, clan, or community leaders—or trolls. Many make the mistake of thinking Killers are antisocial or without friends, but this isn't too often the case. Even the more hostile and aggressive Killers can inspire a sort of hero-worship by less-talented Killers or Achievers; and, believe it or not, some Killers are actually genuinely nice people who simply thrive on competition. In either case, a bored Killer can be a threat to the community, as their natural drive to compete and sometimes (or frequently) abrasive attitude will push them to stir up trouble even when they don't really mean to.
In addition to helping players define their game-playing preferences, the Bartle Test has also been used by game designers to help define the requirements of games that are intended to appeal to a particular audience.
In 2006, after running for ten years on a web server maintained by Erwin Andreasen, the database met with intractable scalability problems. After several months, the test was rewritten and moved to GamerDNA servers, preserving all the original test data.
Expanded categories 
Richard Bartle also created an 8-part version of his player types model for virtual world players.
According to Bartle: "The 4-part version is easy to draw because it's 2D, but the 8-part one is 3D; it's therefore much harder to draw in such a way as it doesn't collapse in a mass of lines." There is no known online test based on this model.
Bartle's divisions provide a foundation for investigating gamer psychology; however, subsequent studies have noted certain limitations. For example, Nick Yee has argued that a 'component' framework provides more explanatory power than a 'category' framework. Jon Radoff has proposed a new four-quadrant model of player motivations that has a goal of combining simplicity along with the major motivational elements that apply to all games (multiplayer or otherwise).
- Richard Bartle (1996), "Hearts, Clubs, Diamonds, Spades: Players Who suit MUDs," http://www.mud.co.uk/richard/hcds.htm
- Andreasen, Erwin. "Erwin's MUD resources page". Retrieved 2009-09-20.
- Erwin Andreasen; Brandon Downey (August 2001). "The Mud Personality Test". The Mud Companion (1): 33–35. ISSN 1499-1071.
- MMO RPGDOT, "Random Dialog: You Shuffle, I'll Deal," http://www.mmorpgdot.com/index.php?hsaction=10053&ID=951
- Bartle, Richard (2003). Designing Virtual Worlds. New Riders. p. 145. ISBN 0-13-101816-7. "I'm often asked about the Bartle Test, on the grounds that because it bears my name I must be responsible for it. Sadly, I'm not. The test is the brainchild of Erwin S. Andreasen and Brandon A. Downey, who wrote it in response to my player types paper so as to test the theory. The Bartle Test is an online binary-choice questionnaire that players of virtual worlds can take to discover what player type they are. As such, it offers potentially very useful information for designers."
- Nick Yee, Gamasutra (Sept. 21, 2004), "Unmasking the Avatar: The Demographics of MMO Player Motivations, In-Game Preferences, and Attrition"
- Radoff, Jon. April 2011. Game On: Energize Your Business with Social Games. ISBN 978-0-470-93626-9.
- Bartle Test of Gamer Psychology, GamerDNA, Retrieved 9-19-2009
- Mulligan & Patrovsky (2003), Developing Online Games: An Insider's Guide, "Appendix C: The Bartle Quotient Survey Questions and Some Results," ISBN 1-59273-000-0
- Taylor, T.L. (2006-02-24). Play Between Worlds: Exploring Online Game Culture. The MIT Press. p. 69. ISBN 0262201631.
- Dave Rickey (2003), "Let the Gears Begin," Engines of Creation #1, http://www.skotos.net/articles/engines01.shtml
- Bartle, Richard (2008-11-25). "8 Types". QBlog. Retrieved 2009-09-20. (Bartle's personal blog.)
- Radoff, Jon. "Game Player Motivations." May 2011. http://radoff.com/blog/2011/05/19/game-player-motivations/