Jasper has started barking at traffic. Specifically lorries/ambulances. They go past, and he barks and lunges. He caught me unawares the first time and nearly got flattened for his troubles. This has literally started this week. I suspect he has been spooked on a walk with my DH, although DH can't think of anything that will have caused this. I could really do without him developing another neurotic behaviour. Any advice?