Hi! Thanks so much for your question.
 
I have had experience in taking Psych 326, as my PI suggested this class when I approached them about getting credit for research, and overall it was fairly straightforward and simple. There are no lecture/discussion components (just like Psych 422), so I just spent time continuing my work as a research assistant under some projects going on in my lab. I assume that your responsibilities will depend on the leniency and policies of your PI/mentor, but in my case, it felt like I was going to lab just as I was before, but just getting credit for it! At the end of the semester, my PI graded me based on my commitment to the lab according to what we had discussed at the beginning of the semester. 
 
Both Psych 326 and Psych 422 would require your PI’s approval, but Psych 422 would also require further approval of an application by the Psychology SAA office. Also, Psych 326 requires Psych 230, 240, 250, 260, 270, 280, or 290 as an advisory prerequisite, but I don’t think I had completed it by the time I took Psych 326, and my PI was fine with this and gave me permission for the class anyway. On the other hand, it seems that Psych 422 is more independently focused so it has more advisory prerequisites: Stats 250, 280, or 425; and one of the following: Psych 302, 331, 341, or 342. 
 
Overall, it seems that the major difference between Psych 326 and Psych 422 is that Psych 422 is for “advanced” research and is more focused on students who already have decent research exposure and are interested in creating and designing their own research project, while Psych 326 is intended for students who are more interested in assisting a project.
 
This website provides more detailed information about the process of registering for Psych 326 and Psych 422 as well as their intended audiences. This website describes an intended student for Psych 422 as being of at least junior standing who has already taken either PSYCH 322, 323, 326 or 327 and/or PSYCH 331/332, in addition to having completed at least one “psychology breadth course”.
 
All in all, if you haven’t done so already, I would suggest discussing with your PI (or research mentor) about whether you feel you would be ready for independently directed research (i.e., Psych 422) or would rather continue under an ongoing project (Psych 326) to decide which would be best for you!
 
I hope that helps, and let us know if you have any further questions!
 
-Jasmine, PMH Advisor