I assume they're bred based on sociability.

Of course they do. Evolutionarily speaking, canines made a bargain with humans when they became domesticated. Certain instincts became suppressed as canines became dependent upon humans for sustenance and social interaction.

Same goes for all domesticated livestock and pets. Not totally lost certain instincts, rather suppressed.

That is why I become absolutely furious with humans abuse their pets and their livestock. We have an obligation based upon the evolutionary cooperation.