My 1st Jack was about the smartest dog I've ever been around, which has included many highly trained German Shepard's & Border Collies.
She LOVED playing with balls and was a bit obsessed, but would have never called her hyper. At eight weeks of age she could figure things out and was a wonderful dog that went everywhere with me. She didn't like many people, but never did anything unless bothered. She'd growl in some manner that told over dogs to get the F... out of her way and she'd walk right past them. I've never seen another dog that could growl like her and not get into a fight.
Had her for 14 1/2 years, before Cancer took her. Still miss her....
Have another Jack now that's been a great dog, but not nearly as smart. Still loves playing with balls, but also would not consider ever having been hyper.
Both Jacks were from parents registered with the Jack Russell Terrier Club Association, which has pretty high requirements.
