Some working dogs can become quite neurotic if not given the right stimulants. My sister got a BC pup but kept it as a house pet - it came from working stock and turned out snappy and hyper as it wasn't given enough to do, it ended up being PTS as it went for one of their kids

.
I have Australian Cattle dogs, another high energy and full-on breed. Their instinct to nip hind legs is very strong and many a time they have driven me mad trying to 'help' with the horses

. They also hang onto your trouser legs if they are trying to get a point across

. I love them but they need loads of exercise otherwise they will often get up to no good ..
I also had a Lancashire Heeler, another cattle herding breed. He was an adorable little thing, no trouble, very obedient. But once we were walking in the woods and passed this woman who had very skinny legs and shorts on, and trainers with no socks. Well this little dog just nipped her as she was passing, and drew blood!

He didn't do it in malice, he must have thought her legs looked rather cow-lke - we were mortified but thankfully she was quite good about it!