A Sim's interests are randomly generated when the Sim is created or born in The Sims and The Sims 2. The more points in an interest, the more interested a Sim is in the particular subject. The interests that a Sim has the most points in are the ones they will usually talk about when they initiate a conversation, or be interested in when being talked to. For the most lengthy and constructive conversations, it's best to talk to Sims that have similar interests. Specific interests can be increased by reading magazines,[TS:HD][TS2] but increasing certain interests will force other interests to decrease. Interests in The Sims 2 can also be changed in SimPE.
In the original release of The Sims, there were 8 interests; Travel, Money, Politics, 60's, Weather, Sports, Music, and Outdoors. For children, the first four were replaced by Toys, Aliens, Pets, and School. Interests were initially hidden, and could only be viewed with a cheat code. The Sims: Hot Date expansion pack added 7 more interests that were only available to adults; Exercise, Food, Parties, Style, Hollywood, Technology, and Romance. Interests are viewable via the "Interests" tab on the lower HUD. Hot Date also introduced magazines, which adult Sims can read to change their interests. Gaining an interest point in one subject will cause the Sim to lose an interest point in another.
Interests run on a 10-point scale, from 0 to 10.00. If a Sim has between 0 and 3.0 points in an interest, he or she will react negatively to it, and will lose relationship points with the speaker. He or she is likely to end the conversation, but may just change the subject. Either way, the thought bubble for the interest will have a red X through it. If a Sim has between 3.01 and 6.0 points, he or she will react positively enough to continue the conversation and gain relationship points with the speaker, but is likely to change the subject. The thought bubble for the interest will still have a red X through it. If the Sim has at least 6.01 points in an interest, he or she will react positively, and the thought bubble will not have a red X.
All interests that the Sim has at least 6.01 points in will appear when the player uses the Change Topic interaction. Only adults can use the Change Topic interaction, and they can only use it when they're involved in a group activity. It is not available when two Sims are talking face-to-face or over the phone.
Interests and Maxis-made Sims
In general, Maxis-made Sims have one or two strong interests, and little or no interest in other topics. Taking these Sims to a community lot seems to "unlock" them, so that they will have a full range of interests. Old Town is useful for this, as going there is a family affair, and is free.
The Sims 2
The Sims 2 shipped with 18 interests, and they're the same for all ages. The interests are Paranormal, Sci-Fi, Health, Politics, Culture, Environment, Food, Travel, Weather, Crime, Money, Work, Entertainment, Fashion, Sports, Animals, School, and Toys. A controllable Sim's interests can be found on the Simology panel.
Interests run on a 10-point scale, from 0 to 10.00. In general, Sims with at least four points in an interest will react positively to it. Sims can use the Change Topic interaction, and it is available when they are just chatting with one another, as well as chatting over the phone, or in group activities. When using the Change Topic interaction, the player will be able to choose any interest, regardless of how many points the Sim has in it. However, if several Sims are involved in the conversation, they may also attempt to change the topic, and the Sim who was told to change the topic may not be able to do so instantly.
Sims can and do talk about things other than the 18 interests, but they only do this autonomously. The player can attempt to change the topic back to one of the interests, but cannot attempt to change it to one of these other areas.
Most pre-made playable Sims in The Sims 2 have approximately 90 interest points in total, while most pre-made townies and NPCs, as well as Sims generated either by the player, or the game have approximately 80 interest points in total. However most pre-made playable Sims' interests are not in decimals, while most other Sims' interests are.
Most pre-made young adult, adult, and elder townies in The Sims 2 have exactly 4 interest points in School, Toys, and Sci-Fi, and a 4 or lower in Animals.
When one Sim talks to another, the player can see which interest he or she is talking about by looking in the speech bubble. Each interest is represented by a set of icons, as shown in the table below.
Interests are unlike personality points. It is impossible to have 10 in every single interest because once an interest is increased by one point another one will decrease by 1 point.
Interests can be changed by reading magazines or through the "Share Interests" social interaction. In The Sims 2: FreeTime, they are also affected by gaining or losing enthusiasm in certain hobbies. Interest change corresponds to the amount of enthusiasm that is gained or lost.
The Sims 2: Pets
Pets in The Sims 2: Pets also have interests in their petology. These interests are what cats and dogs bark and meow about. There are 9 interests for Pets: Pets, Scary Things, Food, Outside, Sleeping, Playtime, Weather, Toys, and Animals.
The Urbz: Sims in the City (Handheld)
In The Urbz, interest are conversational topics that appear when talking to an NPC. Out of the 67 topics in the game, three will appear at a time. Choosing each interest will cause two reactions by the Sim: a text dialogue will appear, and the relationship will change by a set amount, depending on the interest chosen.