Depth Perception in Puppies

한 눈 파는 사이에 거실 문을 1cm라도 열어놓으면, Emily can nose her way out and run all the way up the stairs to the 2nd floor in a wink. But she can't come down. Not one step. Coaxing her on the third step felt like cruelty to puppies.

[But it's so far down!]