>>5011212 (OP)Dogs are very complex creatures. They are a lot like us, and that is why they are mans best friend.
I do 100% believe that dogs can show sexual attraction to humans, beyond just the leg humping dominance thing.
I have had quite a few dogs in my life, mainly female dogs since I find them easier to train, less territorial, and more playful. They have often flagged me when they are in heat. They turn their butt towards you, and lift up their tail to the side as they look back at you. It's completely natural, and you just have to turn them away and sternly tell them no. They do not know how to see you until you establish that parent role for them. They will see you as a possible mate, if not trained since they are unaware that you are not just a weird looking dog.
For both male and female dogs, belly rubs are normal and not sexual, however getting too close to their genitals can make them think that you are sexually interested, so just be carefully. Stick to rubbing their chest. Dogs usually lie on their back to cool off, or to show submission. They are not always interested in belly rubs.