Peter Pettigrew's brain as Scabbers

[Maribel]

No: HPFGUIDX 26410

Hello to everybody,

I was reading "Quidditch through the ages" and I have this question, 
hope you have some thougths about the possible answer.

According to it, a wizard's brain who become animagi become the size 
of the animal in which he transforms, also says if it is a small 
animal the brain will be small as well, and soon they're going to 
forget things.

So, if Peter Pettigrew has lived as a rat for 12 years, Why his 
memory is so good? Why he didn't just forget everything? A rat's 
brain is very small.

In the case of Sirius, we know he didn't live as a dog all the time, 
and the brain of a dog is bigger than a rat's, I think.

I would like to hear your opinions about it.

Maribel
PS.- Please, forgiveme for my English, is not my native language.