Avoid this one. They load question after question and each one has like a 5 second timer before you can move to the next one. The number of questions are relentless and, as I found out, they will complete the study if you are inactive for a set amount of time. I had to stop for a moment to rest my eyes and the study completed, gave me a code, and then wham I get a rejection. I advised why I stopped and asked for a return, will update. For now though, avoid this one.
They did let me return but they didn't let me know I had to discover it on my own. So unless you can focus for a long time on repetitive questions, I would avoid this...the pay wasn't that great for the effort anyway.