We tried a “dog vision” filter to emulate the way a dog sees the world. We used the filter to see if we could predict which toy Magnus would pick out. Human eyes have three different types of cones, which allows us to identify combinations of red, blue, and green. Dogs, on the other hand, have only two types of cones, which means they can only discern blue and yellow. As a result, dogs are red-green colour blind. While humans have more cones, allowing us to see all the colours of the rainbow in