I'm not sure whether this is a rant, or informing or both. Let me know if it's a bit too much on the ranting side, I'll edit it.
> Wait, does participating in a study as a subject count for credit, or does working on a study count?
There was this course called "measurements and diagnostics" and for that you had to pass the theory/tutorials of the course and also 10 hours of being a participant in research. If you didn't do the 10 hours of participation, you could do them at any moment you want and if you completed it, you immediately passed the course.
My university has about 400 psychology students, so that is 4000 hours worth of people participating per year. And I'm pretty sure that more universities are doing this. In The Netherlands alone I estimate there to be about 40000 psychology students per year and probably about 5 hours of compulsory 'participation' in experimental studies. So a tiny country like The Netherlands is skewing this particular bias about 20000 participant hours per year.
Participating in experimental studies is quite fun (pro tip: go for the fMRI and EEG studies ASAP! ;-) ), but I didn't appreciate how I was forced to do it. I didn't learn too much from those experiments and I felt used. It furthermore is a way to be lazy regarding participant recruitment. I'm pretty sure that some startup could disrupt this particular problem. If you have ideas about it, email me, I'm willing to brainstorm and help you to look for ways to solve this problem.
> Aren't studies explicit about the demographics of their participants? And don't studies that make generalized claims usually control for things like gender and age?
Studies are explicit about the demographics, which is why the WEIRD article could be written. And yes they do control for things like gender and age and in general they are quite careful making those claims. The issue is though as a research field psychology isn't the study of the human mind and human behavior but of WEIRD people their mind and WEIRD people their behavior.
Like a lot of societal issues that are in popular media today, this is a systemic issue. Though I could imagine psychology researchers being like: "Hmm, I could get a representative group or I could just get some psychology students and churn my next paper out twice as fast!"