I came across this post recently and it reminded me of one of the "games" that I played as a little kid.
I think I was probably 8 or 9 - old enough that I didn't need to be watched constantly, young enough that I wasn't allowed to wander too far afield. I roped my younger neighbor into a long-running study whereby we waved enthusiastically at every single person who drove by and dutifully recorded whether they waved back, did a weird non-wave acknowledgement of our existence, or ignored us. For maximum coverage, I would station my neighbor by her house (she wasn't allow to go as far as I could) and then position myself at a crossroad at the end of our street to capture anyone who didn't pass her. I couldn't do this for long, because she would get bored and wander off. She also didn't care about confounding variables (what was the difference between strangers vs. people you knew?). Quite frustrating.
I'm pretty sure I made up this little study entirely of my own volition. Science at my elementary school was more along the lines of "fill in this worksheet" and if we were especially lucky, "build this thing according to very specific instructions."
I don't remember how the actual tallies ended up. As I recall, they filled several pages - pretty impressive considering how few motorists actually rolled through in any given time. I'm sure my parents came across an old notebook filled with hatch marks in columns entitled "Yes" "No" and "Other" years later and chucked it without a second thought, so my epic First Experiment has been lost to history.