Drugged Bees Still Find Their Way Home!
Kidnapped, drugged, and left abandoned in a field, bees can still find their way home using mental maps of their surroundings, according to a new study that could pose a major challenge to current thinking about human memory and cognition. [click image to enlarge]. Curious to know more about the insects’ navigational abilities, a team of biologists and psychologists fit 57 bees with radio transponders to track their paths and then trained them to find a feeder 300 meters from their hive. Once the insects knew the route, the researchers captured the bees and placed about half of them into a dark box for 6 hours. They anesthetized the others, disrupting their sense of time and, as a result, their ability to use the sun’s position in the sky to navigate. After a 6-hour delay and a move to a new location 600 meters from the hive, the experimenters released their captives. The paths that the drugged and undrugged groups took at first differed, reflecting the foggy bees’ skewed sense of time (imagine waking at sunset thinking it was sunrise and trying to find north), but the drugged bees soon corrected. Both groups ended up on similar paths, returned to the hive about the same time, and returned in similar numbers: Twenty-nine of 36 drugged bees and 18 of 21 sober bees made it back to the hive. That means the insects weren’t relying solely on the sun to navigate and instead must be using mental maps, the team reports online today in the Proceedings of the National Academy of Sciences. Bees don’t have the brain structure, called the hippocampus, thought to store the spatial memories underlying mental maps in humans. So psychologists may have to rethink how we ourselves navigate, even when we’re not drugged and kidnapped on the way home. Way-finding in displaced clock-shifted bees proves bees use a cognitive map. The question of the computational capacities of the brains of widely separated genera of animals is of interest to behavioral biologists, comparative psychologists, computational neuroscientists, philosophers of mind, and—we believe—much of the scientific community. Half a century ago, the claim that any nonhuman animal had a cognitive map was deeply controversial. If true, it greatly favored a computational theory of mind, as opposed to an anti-representational behaviorist theory. Now that it is well established by behavioral and neurobiological evidence that rodents have a metric cognitive map, the question of whether insects do is a frontier question, the answer to which has broad implications in several disciplines. Mammals navigate by means of a metric cognitive map. Insects, most notably bees and ants, are also impressive navigators. The question whether they, too, have a metric cognitive map is important to cognitive science and neuroscience. Experimentally captured and displaced bees often depart from the release site in the compass direction they were bent on before their capture, even though this no longer heads them toward their goal. When they discover their error, however, the bees set off more or less directly toward their goal. This ability to orient toward a goal from an arbitrary point in the familiar environment is evidence that they have an integrated metric map of the experienced environment. We report a test of an alternative hypothesis, which is that all the bees have in memory is a collection of snapshots that enable them to recognize different landmarks and, associated with each such snapshot, a sun-compass–referenced home vector derived from dead reckoning done before and after previous visits to the landmark. We show that a large shift in the sun-compass rapidly induced by general anesthesia does not alter the accuracy or speed of the homeward-oriented flight made after the bees discover the error in their initial post-release flight. This result rules out the sun-referenced home-vector hypothesis, further strengthening the now extensive evidence for a metric cognitive map in bees.Filed under: Science
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