Sarah Byosiere was at a barbecue just outside Melbourne, Australia, when she came up with the idea of presenting optical illusions to dogs. It was 2015, and she was visiting La Trobe University ...

Only those with a keen eye and exceptional attention to detail will be able to spot the hidden dog in this tricky optical illusion ... objects that obstruct your view of the dog.

In fact, only one percent of people can spot the dog within the time limit, making this one of the toughest optical illusions ever. The challenge is to spot the dog in a herd of cows within less ...