60-Second Science

Cockroaches Smarter At Dusk Than Dawn

For reasons still mysterious, cockroaches have an inability to learn in the morning, but can learn well in the evening. Steve Mirsky reports.

“Gregor Samsa awoke one morning to find that he had been turned into a giant cockroach.”  And a moron.  Franz Kafka couldn’t have known about the moron part because it was just discovered by scientists at Vanderbilt University.  They found that a roach’s ability to learn varies widely over the day.  That’s right—a cockroach is a genius in the evening, but a dolt at daybreak.  The researchers published their finding in the Proceedings of the National Academy of Sciences.

Test cockroaches were taught to get over their hatred for peppermint, by associating it with sugar water, which they really like.  Insects trained in the evening retained their memory of the new sugar water-peppermint association for several days.  But early-to-rise roaches were incapable of learning anything.  Why would an animal be so dumb in the morning?  Said one researcher, “We have no idea.”  Anyway, the discovery that roach memory is so strongly related to its circadian clock could open up new chances to learn more about how memory and biological clocks work together at the molecular level, as well as about learning in general.

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