Dogs show affection by barking, smiling, jumping and licking. Dogs may also show affection through tail wagging. However, a dog may also wag its tail as a sign of uncertainty, nervousness or fear.
Dogs use facial expressions, such as smiling, to indicate happiness and affection, much like humans do. Dogs that bark or jump may simply be trying to engage in a form of play, which is a way in which they show affection toward other dogs or humans. Dogs also show affection in other ways, such as sleeping next to their owners, following their owners around or leaning on them.