The whole question of “should” only arises if you have a choice and a mind powerful enough to reason about it. If you watch dogs it does sometimes look like they are choosing. For example if two people call a dog simultaneously it will look here, look there, pause and think (it looks like) and then go for one of the people. But I doubt it has reasoned out the choice, it has probably just gone with whatever emotion strikes it at the key moment.
The whole question of “should” only arises if you have a choice and a mind powerful enough to reason about it. If you watch dogs it does sometimes look like they are choosing. For example if two people call a dog simultaneously it will look here, look there, pause and think (it looks like) and then go for one of the people. But I doubt it has reasoned out the choice, it has probably just gone with whatever emotion strikes it at the key moment.