What was surprising, however, was just how clear the results of the study were. During the first week of the experiment, no crabs got to the end of the maze without taking wrong turns, some of them detouring six or seven times. By week four, some could race to the end flawlessly. Even the worst-performing crab took no more than three wrong turns.

To see how the crabs would perform when there was no food in the maze, and thus no trace in the water of a snack to guide them, the researchers waited a couple of weeks and put the crabs back in the maze. They also tested crabs that had never seen the maze.

“The conditioned animals all ran to the end of the maze expecting there to be food,” Dr. Pope said.

In less than eight minutes, they scurried to the maze’s end. The inexperienced crabs, on the other hand, wandered around for up to an hour. Many never made it to the end.

The study shows that even in as little time as one exposure to the maze per week, crabs can learn the way through, and furthermore, that they remember it as much as two weeks later. The fact that the ability seems consistent across individual crabs — in other words, that it is something they can all readily do — means that could be used in future studies about how their environment affects their behavior, a focus of Dr. Pope’s work.