Labs are so popular (and have been for so many years) that bloodlines vary all the way from dumb-as-dirt couch potatoes to nitro-powered field trial lunatics with the brains of a physicist.
You have to figure out what you want, and then examine your pup's pedigree (and meet the parents - always a good idea.)
I kinda like a smart dog that's not QUITE so high drive as a NFC/AFC . . . but that's just me.
Smartest dogs I ever had were all mutts!.....................