One of the informal tests I found interesting was to play some of those "spot the differences in two pictures" games. First do one where the pictures are side b

One of the informal tests I found interesting was to play some of those "spot the differences in two pictures" games. First do one where the pictures are side by side to get your brain used to recognizing differences and hopefully reduce the variable of "how do I even do this". Then do a game where one picture shows up and waits for you to look at it and memorize it, then shows the slightly different picture and let you identify the areas of difference. Finally, have a picture which clearly identifies the differences (by circling them or something), waits for you to intentionally proceed, then shows you a slightly different picture where you select a difference but then have a multiple choice question about what is different (eg "the mailbox color in the first picture was blue/green/red/white") for each. I haven't seen one of these online yet, and I took it as part of a battery of mental health/intelligence tests nearly 20 years ago, but I wonder how hard it would be to make one and conduct studies from it today.