We have Bella, the ultra hyper half Yorkie half Westie. Shes about, um, maybe 7 months old.
MIL keeps insisting if we get her spayed she will calm down and won't be so hyper. True or not?
(This is not affecting our decision to get her spayed, which we are going to do regardless, I was just wondering if MIL was right or not. I personally think her hyperness is just part of her personality.)

well, most dogs do calm down after being fixed - but it's more a question for a dog breeder to see if the breed is naturally boisterous or if it's just a case of youthful energy...

In my experience, Yorkies are hyper as puppies and calm down around a year and a half. I don't know about the Westie in her though. That may make the hyperness worse, if Westies are known to be hyper.

Spaying didn't calm my lab down at all. We brought her home from the vet and as soon as I let her outside to pee for the first time, she took off through the woods...ran circles, and came back in the house. So much for taking it easy.. lol.

I don't think that spaying necessarily calms them down. I think it has more do do with aging. Dogs are routinely spayed around 6 months of age...this is also the age at which many puppies begin to calm down a bit as they near adolescence. Natalie was spayed at 4 months of age, this did nothing to calm her...she was a maniac until she reached about 6 months of age.

Spaying did nothing for my Mom's Pomeranian. She's still as feisty as ever.