I've owned various small animals but for the past 8 or 9 years have only had rats, the first pairs I bought from what was PetsMart when that existed and they had great temperaments, obviously quite nervy at first but soon settled and lived on average to 2 and a half.
My third pair came from a local, in dependent pet shop and they were also fab rats, one slightly more nervous at first but both were real characters. Then I decided I would like to rescue some and got 3 from my local RSPCA, they were about 3 months old, hardly ever handled but 2 out of the 3 became very outgoing and friendly, the other was more independent but was not aggressive in any way, just didn't appreciate human contact so much! I kept 5 of her sons(pregnant when I adopted them) and they were the most amazing rats EVER, handled pretty much from the beginning, very outgoing and people orientated, and the feedback I got from the girls new owners was the same, one said ''what have you done to these rats, they're as mad as trees..in a good way''!!
I currently only have 3, 1 of the brothers, who is 2 and a 3 months and showing his age but still a lovely rat and 2 I got from the infamous PAH. I really shouldn't have got them, they are brother and sister who were the only ones left in their seperate cages and to be honest I felt sorry for them, I imagined someone buying one and keeping it on its own for the rest of its life so I came home with them. They both lived with the others I had at the time, Abbie, the female lived with the sisters and her brother Izzy lived with the remaining brothers(the girls sons and nephews) and all was well until Izzy began bullying the older boys, probably because he is much younger and higher in the pecking order I guess.
So I'm now in the awful situation of having 3 rats who all have to live alone, I obviously can't mix boys and girls and Izzy can't live with the old boy Finn coz he bullies him, they can, however, all be let out together, supervised(unless Abbie is in heat, every 4 days

) and they get on fine and it means they have some rattie interaction.
Anyhoo, I'm rambling, my point was meant to be that I've had quite a few rats from big chain pet shops who have been great but Izzy and Abbie are the most unfriendly rats I've ever owned, and the 'best' ones are those I reared myslef with lots of handling from very early on in their lives. So the idea that ''owners can socialise them'' is rubbish really, especially when they get to say 15/16 weeks, like a pair of boys in my new local PAH, I wonder how much handling they get.
If I was to get more rats, which I'm not(!) I would go to a small hobby breeder who really cares where their babies go and in general about improving rattie health and temperament, we do it with dogs so why not with rats too!
JMO
Emily :)