Dog's Behaviour- New Baby

[FionaBeth]

Hello everyone. I have a black lab who is about four years old. We have a baby that is a few months old. Our dog has adjusted quite well to the new baby, but he is exhibiting some new behaviours recently which I am wondering about.

The other day, the baby, dog and I were all out for a walk. We encountered our neighbour, who my dog has met a few times before. The neighbour greeted my dog first, who reacted very happily (wagging tail, went right up to him). After greeting the dog, the neighbour spoke to my baby for a few minutes. He then returned to my dog. My dog proceeded to back away, bare his teeth and bark at my neighbour. Are these signs of jealousy? Protectiveness?

Our dog is interested in the baby, but he always calms right down around him. We do allow some interaction between the dog and the baby, under complete supervision. Recently, our baby has become more aware of the dog, and will pet him. The dog will lick the baby's hands very gently. However, his lips sometimes start to quiver and he moves his ears back. I have not continued to let the baby pet the dog since this happened because I am not sure what type of behaviour the dog is exhibiting and I want both the baby and dog to be safe.

Any advice would be greatly appreciated!