Gibson trained the pigeons to sit in front of a computer monitor and peck a series of 10 dots. They were rewarded with a snack if they did it efficiently. If they jumped all over the place, no snack.
"It only gets food if it connects all 10 dots efficiently," he said.
The pigeons were pretty good at it, he adds, so now he's gearing up to repeat the experiment in New Hampshire with nutcrackers. He expects them to be much better at it than the pigeons.
That would be strong evidence that nutcrackers do, indeed, create a "cognitive map" of their environment. That's important for reasons other than just retrieving their caches.
"If you take an inefficient route in the natural environment, you increase the exposure to predators, you waste energy, you spend time traveling that could be used in other activities, like reproduction," Gibson said.
His findings might have some practical applications for scientists who are studying human memory, but he admits that's not what drives him.
"Personally, I'm just intrigued by these birds," he said. "I think they're really neat."