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, a child created in-game, not CAS, has seemingly random personality points, usually with high playfulness. In The Sims 2, an in-game child's personality was based on the parent's personality and how the child was raised as a baby. A neglected baby might be more meanspirited, even if both parents are nice, for example.

Personality can be altered in  veriaty of ways. In The Sims, a potion made by the Lab Station would reverse personality points. The only way to get them back would be to recreate the potion. Also, a zombie would have no personality at all. In The Sims 2, an older relative could influence a Sim to change their personality, one point at a time, via the interaction "Encourage...". A zombie in The Sims 2 might have a reversed personality or no personality at all, depending on how much the Grim Reaper was paid.

In The Sims 3, 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. 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.


 * 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.