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 shortly after finishing a master’s degree on canine cognition back home in the US. Chatting at the barbecue with a group of psychologists who were studying how the human brain perceives visual illusions, it struck her that the same approach could provide a window into how dogs see the world around them and how their perception differs from our own. “We had this crazy question of: Could you give a dog an illusion, and would they be able to see it?” she recalls.