The game you are playing now: its cards, its rules and the people round this table. You are the researchers and the researched.
Observation, play, reading the cards, your own account.
The longer story
This card turns the game on itself. Play once with any other Object, then play again with this one: the thing everyone is researching is now the game on the table, and the people round it.
It is a good object because it can be so many things. It is 90 printed cards and a rulebook, which you could read as closely as any text. It is something a group does together, which you could observe. It is an experience, which you could describe. It is a teaching tool, whose effects you could try to measure. It is an argument about what counts as research, made by one person, which you could take apart. And it is something that was designed and redesigned, which its maker could reflect on.
Each of those is a different answer to "what is there to study?", and each leads to a different research question. That is the point the whole game makes, made about itself. One warning: when you study something you are taking part in, you are both researcher and participant. Say so, and say what difference it makes.