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Do you have trouble getting started in the morning? Do you have problems learning early in the day? If you do, you are not alone. Cockroaches have the same problem! They learn better at night than they do in the morning.
To investigate when cockroaches learn best, researchers at Vanderbilt University (Nashville, TN) tested the insects for which odor (peppermint or vanilla) they preferred. Most cockroaches preferred the smell of vanilla to the smell of peppermint at all times. The scientists then trained the cockroaches to prefer the peppermint smell by rewarding the insects with a taste of sugar water when they approached a peppermint smell and punishing them with a taste of salt water when they approached a vanilla smell. (Cockroaches like sugar water, but they don't like salt water.)
When the cockroaches were trained in the early night, they remembered the new associations (peppermint = sugar water; vanilla = salt water) for up to 48 hours. However, if the cockroaches were trained in the early morning, they quickly forgot which smell went with which water. The effect was dependent on when the cockroaches were trained, not when they were tested.
So, cockroaches learn better at night than they do in the morning. Because these animals are more active and search for food during the night (nocturnal), it is likely that information they gather at night will be more useful to them. These experiments provide some clues about the interactions between body rhythms, learning and memory, but the brain pathways involved with these functions are still unknown.
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Copyright © 1996-2007, Eric H. Chudler, University of Washington