Personality

A Sim's personality is determined by their Zodiac signs. In both The Sims and The Sims 2, personality was split into 5 sections: Niceness, neatness or cleanliness, outgoingness, activeness and playfulness. While in The Sims, this did little to the nature of the Sim, it makes quite an impact in The Sims 2.

In The Sims, children get random personality points, usually with high playfulness, when they grow up from being babies. Most townies also get random personality points. In The Sims 2, the personality of children born in-game is based on the parents' personalities, and is affected by how the child was raised as a baby. A neglected baby might be more meanspirited, even if both parents are nice, for example. Adopted children and townies seem to get a random zodiac sign, and the personality associated with it.

Personality can be altered in variety of ways. In The Sims: Livin' Large, the chemistry set can make a potion that reverses personality points. The only way to get them back would be to recreate the potion. A Sim abducted by aliens would return with an altered personality. Sims can change their personality one point at a time by using the Crystal Ball. Also, a zombie would have no personality at all. In The Sims 2, an older relative can influence a Sim to gradually change his or her personality, via the "Encourage..." interaction. A zombie in The Sims 2 might have a reversed personality or no personality at all, depending on the method and conditions that were used to ressurect them.

In The Sims 3, the personality points system was replaced with traits.

Qualities

 * Shy/Outgoing


 * Outgoing Sims will often use a mirror autonomously. The social bar of outgoing Sims decays rapidly, as they desire social interaction. Due to their social nature, outgoing Sims gain Charisma faster.


 * Shy Sims dislike social activities, and if told to do so, will often grimace at the camera, and walk to the activity slowly with head bowed. Their social bar decays more slowly.


 * Mean/Nice


 * Nice Sims are usually kinder to other Sims, and will probably respond positively to a social interaction, even if they aren't interested in it.


 * Mean Sims are more likely to cheat in games and react negatively to social interactions.


 * Serious/Playful


 * Playful Sims can jump on sofas and play in bathtubs. They will also be able to skip to get somewhere.


 * Serious Sims dislike watching TV and prefer reading. Should such a Sim be told to read they will smile at the camera and punch the air. However, though serious Sims autonomously choose reading and the like over TV, the actual gain to Fun from watching the TV is no different than if a Playful Sim watched it. Serious Sims also gain Logic faster, while Playful Sims gain Creativity faster.


 * Sloppy/Neat


 * Neat or Clean Sims like cleaning activities, even gaining Fun from doing them. They are more likely to clean or make beds autonomously, and may autonomously 'groom self' in the mirror. They are more likely to flush toilets autonomously, and in The Sims, are more likely to autonomously wash their hands after using the toilet. Because of their clean attitude, their hygiene decays slower. Clean Sims gain the cleaning skill quicker as well.


 * Sloppy Sims prefer to make messes and can also rummage through the trash can for food or simoleons. They dislike cleaning, and actually lose a small bit of fun when forced to do it. Due to their messy nature, their hygiene decays faster, though they seem to care less about it. Also, they tend to flatulate more often than other Sims.

In The Sims 2, this score affects whether or not the Clean interaction appears when clicking on an object that can be cleaned. The neater a Sim is, the less dirty an object has to be before the Clean interaction will appear.


 * Lazy/Active


 * Active Sims lose energy slower than anyone, and they enjoy working out. They will also be able to run to get somewhere. However, due to all this activity, their hunger decays faster too. Active Sims also gain Body skill faster than normal, due to their active nature.


 * Lazy Sims tend to sleep more than other Sims, since their energy bar decays faster. Also, due to their 'couch potato' nature, their comfort decays faster too, making them need to sit or relax more often. And, as a side effect to all of this laziness, their hunger decays slower.