The Sims 3/Traits

Traits
Sims can have up to 5 traits. Traits influence how a Sim feels, what they want, and how they behave. Sims gain more traits as they grow from babies to young adults. If a Sim has postitive experiences as a baby you will be able to pick the Sim's first 2 traits. If they have negative experiences as a baby they will be assigned negative traits. If the baby Sim has been moderately happy growing into a toddler, the traits will be chosen at random. Sims get along better with Sims who have at least one of the same traits.