A key discovery was that if the inside of the mask is smooth - even if the outside is bumpy with pores, a nose and other features - it will stretch over most faces and move with facial muscles.

When a dolphin pressed a certain key with her nose, researchers would throw the corresponding prop into the water.

The idea is that every odor molecule that enters our nose has a specific shape that fits a specific receptor-like a key fits a lock-allowing us to detect, say, the acrid aroma of burnt coffee.