Puzzles and optical illusions don’t just test your analytical skills. They’re also a great way to test your vision.
Optical illusions help us to better understand how our brains work, especially when it comes to processing complex visual information. 
They also stimulate the parts of the brain responsible for intelligence and visual memory. Take a look:
As you can see, this is a black-and-white image of a man standing in what appears to be a small grove of trees. Behind him is a stone structure resembling that seen at Stonehenge. There is also foliage scattered around the edges of the image. 
There’s nothing to miss in this rather detailed image. However, believe it or not, the face of a second man appears in the image. It’s not very well hidden either. 
To make things more difficult, time 9 seconds from now. Ready? Begin.
People who pay attention to detail and are familiar with this type of optical puzzle will manage to complete the task quickly. Otherwise, it may take more than 90 seconds. Did you find it? If not, here’s a hint: look at the image from a different angle.
Quick quiz: Spot the hidden man in 10 seconds