Adulthood

Question
I was told by my vet that a lab is considered and adult at 3 years of age. Recently my neighbors told me different, she claims labs are puppies until they are 4. At what age is a lab considered an adult?

Answer
I would go with the 3 years.  Many of them have really settled down by then and that is when most dog's personalities are mature.  That is not to say some won't take less or more.  

Your neighbor is likely generalizing from only a few or just one.  A common error in many cases.