For my PhD experiment, I am using a video game for my control condition, do I need permission from the video game developer?
If you are using, say, timings of people playing a video game as data in an experiment, as long as you don’t use images from the game or pictures of people playing the game without appropriate permissions, then you’re probably OK, but I’d ask your university’s legal department for advice before starting such experiments. It’s their job to protect the university from ignorant (of the law) researchers like us. If y’all have a law school, go see if there’s a legal clinic that’s there to a specific case like this (research on the edge of legality). Otherwise, I’d check with your grants compliance office since they try to protect you, too. I’d do this even if you’re not grant funded on this project. You are also going to need to run your plans past your institution’s IRB and demonstrate that you human subjects will be treated humanely and according to requirements.
As has been suggested, the license is the place to start. But not the end of the story. Not every possible thing that could be found in a license agreement is reasonable. It has happened that some things in license agreements have been voided by courts.
The details of the license regarding how many people are permitted to use a given copy probably are binding. So if a video game license says "one person" or "three people" or some such, that probably means just that. Lots of software has such limitations. Other possible phrases are "exclusive use" or "non-transferable" and so on.
Also, if you need to copy images or text from the game, the licensing conditions regarding that are probably binding.
There is another aspect to it. Suppose you make use of a video game. And suppose the owner of the copyright decides they don't like that use. You could find yourself inovled in a struggle with lawyers and trips through courts etc. Even supposing you win in the end it could be a horrible time wasting experience. It could put strain on your life, your relationship with your university, etc. If the copyright holder is particularly nasty they can make such things last years.
Far better to get permission in advance. In writing. If you make a polite request to the video game maker and get permission then Research Time! If they say no, or they try to put on conditions that you can't live with, or they don't respond at all, there are other video games.
That depends on what you do with the video. It is probably covered by copyright and it is conceivable that patent law also applies. If you cite things it will help, but reproducing segments of video or image captures from it requires you give thought to fair use and copyright restrictions.
But, if it is software that you have a valid license for, you can use it for its intended purpose without further permission, just as you can use word processing software to write. It is the reproduction of copyrighted content that you need to be concerned with. And, copyright law varies.
Note, especially, that images are a bit special. While you can quote from text, reproducing images has issues since an image can be construed in some cases as "a complete work" even when within another.
Don't even think about reproducing anything that Disney has copyrighted.