Algodoo

I expected that the circles would all start out at the same brightness and that "w" would increase the brightness of one circle slightly each time "w" was pressed. In that case you could get a measurement of your brightness sensitivity.

Another approach would be to not hide the circles. Each time a user clicks on what he thinks is the brighter circle, one of the four circles randomly becomes the brightest circle. If the user doesn't get n in a row correct, then the brightness gets incremented. The scene finishes when the user gets n in a row correct. The scene then reports a value of the users brightness sensitivity. n = 4 or 5 might be a good starting point.

s_noonan - I was aware I should have implemented randomness and color changes, but couldnt be bothered at the time cause I was tired. I'll see what I can do now.

I chose to hide the circles because I only wanted the player to see them for a brief instant. That's what this test was about, the diminished ability to tell contrast apart with shortened exposure to the contrasting colors.

I think I understand now. It's not about detecting the smallest perceivable contrast difference. It's about how your brain processes contrast differences when the sample time is short. I should have paid closer attention to the description.