I think Gally's explanation is a good one, as it relates to the actual breed you are researching.
This reminds me of woman I saw at a recent ob fun match. She had an English Cocker, on lead, walking through the building but outside of the ring areas. As the woman moved along at a fairly fast pace, the dog's nose was glued to the ground, and he was furiously zig zagging back and forth at the greatest distance the 6' leash would allow. All I heard from the woman was a STEADY stream of "leave it !! here !! leave it !! leave it !! leave it !! here !! leave it !! leave it !!", combined with intermittent yanks on the leash. The dog was completely oblivious to the onslaught of verbal gobbledeegook and the lame attempts at physical correction, of course.but also when you don't give it time to use it's instincts?