This is quite possibly one of the stupidest things I've seen. They're putting these kids in an unusual situation. They're in an unusual place surrounded by authority figures (a cop and their parents)
The article states,
We wanted to test a group of children to see what would happen if we planted a real gun in their mix of toys.Well there's problem # 1. You're fucking up the entire experiment by deliberately putting a gun in with a bunch of toys. Also, and this should be common sense, kids will react with curiosity unless you teach them how they should react. If you haven't discussed firearms with your kids how can you expect them to instinctually consider them dangerous, not touch them, or come and tell an adult? Kids are naturally curious. If they've never seen, touched, or held a real gun before how would you expect them to know it's not a toy? (especially in this case, where you've deliberately placed it in a box of toys.)
What do most little boys do with toy guns, or their fingers? They point them at each other and go "bang, bang, bang." That's exactly what I'd expect to happen. The adults conducting this "experiment" set it up to ensure they'd achieve the result they wanted.
All non-instinctual behaviors are learned. Life is all about learning how to respond to different situations. If one of the kids in that class had been taught to respect firearms the outcome would have been very different. Put a 12 year old in that class who goes shooting with his dad every Saturday and who helps his father clean his pistols and you'll have a decidedly different outcome. That 12 year old might pick it up, drop the mag, check the chamber, and then go hand it to an adult.
Put a bunch of adults with NO firearms experience in a similar situation and I wouldn't be the least bit surprised if the person who found it immediately started pointing it at people. Hell, my dad did exactly that once. He jokingly pointed a pistol at my mom years ago and said "don't worry it's not loaded" nevermind that my dad knows nothing about guns and almost assuredly didn't check whether it was loaded...... and I wonder why my mom is afraid of guns.