It's not hard to be a fan of optical illusions when they are so entertaining. And while some mind-bogglers have been meticulously designed and created, others are discovered by chance – just like these four accidental head-spinners.
From levitating boats to three-headed deers, for this piece we have chosen the best and most confusing illusions that weren't made by design. But if you're a fan of brain-frazzlers that have been carefully created, then our roundup of the best optical illusions of all time will be right up your street.
01. Floating boat illusion
This utterly bizarre phenomenon has been bending everyone's mind, as it looks like boats out at sea are levitating. We have covered the peculiar 'Fata Morgana' phenomenon (meaning 'mirage' in Italian) a few times, but we still think it's fascinating.
The natural-occurring illusion is caused when cold air sits below warm air directly above the sea. This atmosphere above the sea level bends the light and distorts the image for onlookers along the shoreline, resulting in it looking as though the boat is floating well above the sea.
02. Cat stairs
The internet is utterly jam-packed with cat content, so it should come as no surprise to see a feline-themed illusion make it to our list. This particular mind-boggler begs the question, is the cat walking up the stairs or down the stairs? Despite the fact that this illusion has been doing the rounds online for years, no one seems to know which direction it's walking.
Supposedly, the direction that you see the cat walking is dependent on your personality. If it looks as though it's heading upstairs then you're more likely to be optimistic, whereas if the cat is coming down the stairs, then you're more pessimistic – although, we wouldn't take that as gospel.
03. Three-headed deer
This accidental optical illusion looks like something straight out of Nordic mythology. Back in 2014, Renatas Jakaitis managed to perfectly capture the moment that three aligned deer looked at the camera, resulting in an image of what looks like a mystical Christmas beast.
Jakaitis has said, "When I took the picture I didn’t even notice it. It was only when I looked back at the images on my camera that I realised". Deers are known for walking in paths, so it makes sense that Jakaitis was able to capture this stunning moment where the creatures were all lined up with each other.
04. Changing hat illusion
This accidental optical illusion of a colour-changing hat was shared on TikTok. User oteliacarmen walks her newly bought hat around her home which gradually changes colour from brown to green under different lighting.
The shift in colours is caused by Metamerism, which basically means that the different lighting affected the way our eyes perceived the shade of the hat. Despite contacting the store and the manufacturer, the user has still not discovered what colour the hat is actually supposed to be.