Where temperament is concerned, you can start seeing signs early on. Bold, friendly, curious, explorative, not easily stressed are traits you want to look for. You want to avoid shyness (keeping in mind there's a difference between new animal settling in and true shyness), easily stressed, fearful, aggressive, overly pushy andr obnoxious, possessive. You'll start seeing these behaviors as early as 12 weeks, and them peak between 6 and 8 months.