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 love to perform social interactions and often exhibit happy reactions when the player commands them to socialize. They 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, particularly if they are nice as well. Sims who are extremely Outgoing (8 points or higher) will enter hot tubs naked, assuming there are no Teens or Children around.


 * 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. Also, while walking from place to place, Shy Sims sometimes wring their hands and look anxious; this is one way to identify shyness in townies and NPCs. They are fearful about diving into pools and will often back away off the diving board after getting on it. The main benefit of shyness is that a Sim's social bar decays more slowly.


 * Grouchy/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. For example, Nice Sims are likely to accept the "Admire" interaction from other Sims even if they don't know each other well. Also, Nice Sims will listen politely to Grilled Cheese Sims talk about grilled cheese even if they aren't interested in it themselves (most Sims really don't want to hear about grilled cheese unless they share that aspiration).


 * Grouchy Sims are more likely to cheat in games and react negatively to social interactions. They are also more likely to initiate negative interactions with other Sims (teasing, pranking Sims they don't know, etc.)


 * Serious/Playful


 * Playful Sims can jump on sofas, play in bathtubs, and even play with refrigerator doors. They can also skip from place to place; players can have them do this by clicking on the ground and selecting "Skip Here," which is faster than walking, though not as fast as running.


 * 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 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 exercise good table manners (the drawback to that is that it takes them longer to eat) and are likely to wash their dishes when finished, sometimes even cleaning up other dishes at the same time. 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. Neat Sims gain the cleaning skill more quickly as well. Sims who are extremely Neat have a special feature: they create sparkly bubbles when they clean household objects.


 * 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, and objects such as showers and counters get dirty more quickly when Sloppy Sims use them. If they are very Sloppy, they tend to generate large puddles around the showers and bathtubs they use. Sloppy Sims eat messily (but quickly), and they tend to flatulate more often than other Sims; both of these activities will disgust any Neat Sims who happen to notice them. Another drawback is that Sloppy Sims may autonomously eat rotten food, which can of course make them sick. However, one benefit is that a Sloppy Sim will autonomously take a sponge bath in the nearest sink if her hygiene drops low enough; this can come in handy if no shower or tub is available. (Sloppy Sims can only do this via free will, not on command.)

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 (lazier Sims will only run if the location they're going to is far away). 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, and their fitness level goes up more quickly when they exercise.


 * Lazy Sims can be identified by the slouched posture they take on when standing still. Their energy motive is slow to decay, but it also takes longer to replenish, meaning that when they go to sleep they tend to stay in bed longer than Active Sims do. 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 more slowly. The Logic skill comes most naturally to Lazy Sims, since building that skill involves mostly sedentary activities.