The OP here raises a very interesting question, but I can't help but be distracted by the phrasing. Humans are both decision-making agents and complex biochemical systems so my poor pedantic brain is spinning it's wheels trying to turn that into a dichotomy. If it were me I would have said Subject v Object, especially since this ties into objectification, but that's a nitpick too minor for me not to upvote it. Anyway...

Personally I lean towards a "complex systems" model of other humans. People can surprise you, pleasantly or unpleasantly, in how they react to things, but then again you could say the same about any sufficiently complex process. And it's not very hard to learn patterns to predict how people (or groups of people) react to a given class of stimulus if you're empathetic and observant, just like with animals and computers. I consider it one of my better qualities that I can usually guess the inputs people are looking for when they talk to me and subtly work them into the conversation; it sounds somewhat artificial when put in those words but its actually a really intuitive process once you get the hang of it.