In his book Cognition in the Wild, Ed Hutchins published what is probably one of the most fascinating analyses of ship navigation ever written. I was reminded of it when we took the M/S Silja Serenade from Helsinki to Stockholm.

Hutchins explores how systems that are larger than an individual person “think”. He is concerned with how these larger systems operate and how such a system computes by propagating representational states across its parts.

The Silja boat is a good example. It’s so big, its four corners occupy different GPS coordinates on a map. Steering it successfully through one of the densest archipelagos in the world is impossible for any single individual. It requires what Hutchins calls distributed cognition.

The boat is huge–well over two football fields long, and there are cabins for 3,000 passengers. Our cabin was on the 11th floor!

Early in the morning we got a special invitation to visit the bridge. Our hostess explained it would be like visiting a church. She was right! After climbing a series of restricted-access stairs and passing through several well-locked doors, we emerged beside the captain and his first mate, high above the rest of the ship.

We saw a full panorama view of the hundreds of islands that make the archipelago so spectacular, many of them startlingly close. And the blue water somewhere far, far below. The passage ahead seemed impossibly narrow.

I asked if anything unexpected ever happened. The first mate said almost every time something does. For instance, that night the stabilizers hadn’t been working as expected. Still, in the last 25 years he said there had only been a single occasion when the ship had not made it to port.

The most unpredictable element is the wind, he explained. The ship is 32 meters wide. But in strong wind it lists and goes diagonal. Suddenly it needs 70 meters to pass through a narrow passage. The narrowest strait (Kustaanmiekka) is only 81 meters wide! I checked.

According to Ed Hutchins, “the members of the navigation team form a flexible connective tissue that maintains the propagation of representational state in the face of a range of potentially disruptive events.”

That’s why there are always at least two pilots on the bridge.