Heelers by and large are very smart but lack non-situational awareness, meaning if they are engaged in a task they are brilliant; in the space between they get anxious and needy, looking for the next task.
My Labs have been the absolute kindest souls to ever visit the Earth but, unlike 59's pup, only knew time in terms of naps...they were more Wheel of Fortune than Jeopardy.
Jack Russel's: We are on our third (my fourth) and if bluster was IQ, we'd know all about the Sixth Dimension. It is not so we don't. JR's operate like a Patriot Missile: See the target, kill the target, next.
The new rescue is, and I know I have been posting too many pictures of her, is the smartest, most in tune dog I have ever owned in my life. She is a cross between a Heeler (which she was marketed as - she is maybe 25%), a GS and whatever dog, like a Standard Poodle, has common sense...throw in mutt for some savvy and that is her.
We got really lucky.