What is the difference between "subject" and "object" of study/research?

Question

Let's say that I collected data on a person: his favourites, character, attributes, behaviour, etc. Was he the subject or object of my study/research?

Next, I collect data on an ethnic community: their culture. Is this ethnic community the subject or the object of my study/research?

Finally, I will collect data on a mountain (non-living): it's height, it's history, etc. Will this mountain be the subject or the object of my study/research?

I looked up the two words in an Oxford dictionary and I found similar meanings:

1. Subject:
   a person or thing that is being discussed, described, or dealt with.
   "I've said all there is to be said on the subject"
   
2. Object:
   a person or thing to which a specified action or feeling is directed.
   "disease became the object of investigation"

Answer 1

I had the same question. It's a strange shift of meanings, and it doesn't end with scientific research. "Subject" also means "a person ruled over by another, especially a monarch or state authority" (Wiktionary), but since it is ruled over we can say it's actually an object.

I couldn't find any research on this point. But I figured out some arguments myself:

1. Use "subject" when you passively observe it. Use "object" when you actively affect it and change its behavior.

   Yes, an object is "a person or thing to which a specified action is directed". But just an observation is hardly counts as an action. If a person continues to act by his own will and you just register its behavior then he is still a subject. He continues to do it regardless of your presence and observation.

   The same argument applies to communities. And it can be extended to a mountain too. Until you perform some actions to change the natural order of things (e.g. you detonate explosions in order to observe an avalanche), it's still a subject.

   Sure, ideal passive observation is impossible (see e.g. observer effect), But you should at least clarify your intentions.

2. Use "subject" for persons and high-developed animals. Or define "object" more precisely.

   "Object" has a negative connotation since you objectivize it. Yes, as a researcher you strive towards objectivity. But "object" sounds unethical. So, I'd use "subject" for persons and animals regardless of the distinction made in #1.

   On the other hand, generally you don't research a subject as the whole. In your example, you actually study a person's favorites, character, attributes and behavior. So you can say that favorites, character etc. are objects of your research. And then you don't need to talk about the subject at all.

This answer also proposes to use "agent" for a person taking an active role in an experiment.