You assume it’s just a twig or the wind but the dog knows better. For there perception of reality is deeper then ours as their sense of smell, hearing and animal instinct might see things in a different realm that we couldn’t perceive on our own. Who knows how many times that bark or pull away led us away from a path of darkness that could have trapped us. Recent scientific studies have shown that dogs sense of smell can perceive Cancer in one’s body better then many machines, what else can they perceive? The Dog knows more then we think and maybe we should start listening before it’s too late.