The Sims

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The Sims
Developer: Maxis
Publisher: Electronic Arts
Year: 2000
Platforms: PC, Macintosh, PS2, Xbox, GameCube
Genre: Simulation
AI Era: (see era list)

The Sims is a life-simulation game designed by Will Wright in which the player has control over semi-autonomous people as well as the design of their house (architecture and interior design).


Description of AI Behavior

Sim characters are semi-autonomous and attempt to lead normal lives involving eating, sleeping, bathing, going to the bathroom, working, having fun, and participating in relationships.

Notable Behaviors

The Sims ability to autonomously participate in daily activities regardless of the arrangement of the environment is impressive. In particular, Sim characters can intelligently interact with any object in the game since the interaction logic is stored within each object rather than inside the Sim (Smart Object / Smart Terrain architecture). Moreover, each Sim has a somewhat complex architecture involving Personalities and Needs that help drive the Sim through everyday life.


Agent Architecture

Sims have four key aspects to their personal agent architecture: Personality, Needs, Skills, and Relationships.


Each Sim has individual ratings across five personality traits. The traits are: Sloppy to Neat, Shy to Outgoing, Serious to Playful, Lazy to Active, and Mean to Nice.

Personality traits affect what Sims choose to do autonomously and how much benefit a Sim receives from a given interaction. For example, a serious Sim will derive more "fun" from playing chess than playing a pinball machine.


Sims have two classes of Needs: Physical and Mental. Physical needs include Hunger, Comfort, Hygiene, and Bladder. Mental needs include Energy, Fun, Social, and Room.

Each Need is rated on a scale of -100 to 100 based on the history of the Sim. For example, if the Sim is fully rested, his Energy is at 100. All eight needs are weighted through individual Response Curves and summed together to generate an overall Mood (on a scale from -100 to 100).


Sims can acquire various degrees of Skills which affect their interactions. Skills include Cooking, Mechanical, Charisma, Body, Logic, Creativity, and Cleaning. For example, if a Sim has a low Cooking skill, they will catch the stove on fire when they try to cook.



Smart Objects and Smart Terrain


Each inanimate object in the game (that the Sim can interact with) contains two important categories of information: what benefit the object can provide for the Sim and how the Sim interacts with the object. Each object, in affect, broadcasts its benefit to nearby Sims. For example, the toilet broadcasts that it can increase Mood by 26, if urinated in will increase Bladder by 40, if cleaned will increase the Room score by 30, and if unclogged will increase the Room score by 40. Further, the toilet contains the animations and step-by-step instructions on how the Sim can use the Toilet for each action (urinate, clean, or unclog). This architecture allows Sims to intelligently use any combination or variations of objects and also allows for expansion packs of unanticipated objects without updating the main game code.

Within Maxis, the "terrain" created by various objects broadcasting their services is called the "Happyscape" and is loosely referred to as Smart Terrain.

Some objects, such as food, need to be processed before they can be directly used by the Sim. In this case, the food contains instructions on how it needs to be prepared (for example, cooked) before the Sim can eat it. In fact, eating is a complex process that pulls the Sim from one activity to another in the following manner. First, the Sim is hungry and the refrigerator broadcasts that it contains food. The Sim uses the refrigerator and gets the food. The food tells that Sim that it must be cooked and the stove broadcasts that it can cook food. After using the stove, the cooked food directs the Sim to place the food on a table surface and the Sim must sit down to eat it. Once the Sim is done, he will dispose of the leftover food if they happen to have a Neat personality (otherwise the dirty dish will sit on the table, flies will come, and the Room score will be decreased).


What Worked


Individual Good Thing


What Didn't Work


Individual Bad Thing


Lessons Learned


Reception by Public

The Sims became the best selling PC game in history when it came out, selling more than 6.3 million copies.


The Sims on Wikipedia.

External Links


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