In the early 20th century, millions of chickens wore rose-coloured eyeglasses so they wouldn’t turn into cannibals.
Domesticated chickens in very close quarters develop behavioural problems. Normal exploratory pecking becomes aggressive and damaging; chickens lose their feathers and sometimes their lives. Yep, chicken cannibalism is totally a thing.
(Maybe skip this parenthetical if you’re squeamish. Cannibal chickens often attack the cloaca of other chickens immediately after the victim produces an egg. It’s called – rather euphemistically – vent pecking. This behaviour is probably triggered by the appearance of exposed mucous membranes around the cloaca, and is precisely as gross as you’re imagining.)
Chicken farmers have a range of solutions to this problem. The best and most obvious one is to… you know… not put the chickens in such crowded conditions. But instead of that, some farmers will chop off the ends of chickens’ beaks; dim the lights to calm the chickens down; or literally bolt blinders through chickens’ nostrils so they cannot see directly in front of themselves. (Fortunately, some of these practices are illegal now under various countries’ animal welfare laws, with good reason.)
In 1903 an inventor named Andrew Jackson Jr. (no relation to the US president, I hope) patented a slightly less creepy and definitely more adorable solution: chicken eyeglasses. These protected chicken eyes from attack, but it was followed a few years later by a fascinating innovation: rose-tinted chicken eyeglasses. The logic was impeccable. Chickens peck when they see red – blood or mucosa. If you put rose-coloured glasses on, everything looks red. So the chicken cannot see blood, so they don’t peck, and they don’t start to eat other chickens.
I don’t think anyone has actually put this logic to a scientific test. It seems dubious to me. But that didn’t stop various chicken eyeglass companies selling millions of chicken eyeglasses in the mid-20th century.