Mind-bending optical illusion tests your eyesight with 16 hidden animal and human faces – how many can you spot?

THIS mind-bending optical illusion will certainly test your eyesight - and your patience.

Hidden in this historical brain teaser titled The Puzzled Fox are 16 animal and human faces - but how many can you spot?

The sweet woodland scene shows the cunning animal appearing to climb a tree as three eagle-eyed birds watch on.

But camouflaged among the greenery, 12 other pairs of eyes are secretly staring back at you.

Fear not if you struggle to spot any - as the brain teaser has been puzzling illusion lovers since US printmakers Currier and Ives produced it in 1872.

Now nearly 150 years on, The Puzzled Fox has reared its perplexing head again to challenge a fresh audience.

The fox is surrounded by other animals - including a horse, lamb and a now-extinct passenger pigeon.

A sheep can also be seen nestling at the base of the tree, while a boar is lurking in the undergrowth.

A trio of human faces are also disguised by the tree trunk on the left, while another two grace the tree on the right.

And there are a couple more faces veiled by the forest floor to decipher too.

The baffling optical illusion left many viewers rubbing their eyes in angst after struggling to spot the hidden heads.

If you enjoy racking your brain, why not try this brain teaser and see if you can spot the cat concealed in this image.

And if you want to further prove your detective skills, this optical illusion is hiding an animal in plain sight - but can you see it?