To do so, they first taught the rodents to distinguish long and short sounds. After this training, the rats were then presented with two alternatives: If they participated in the test and mastered the task, they received a great reward in the form of six pellets. If they were wrong in their answer, they received nothing. On the other hand, if they decided against taking part in the test from the start, they were given three pellets of food. During the individual test series, the degree of difficulty of the tasks increased more and more. If the eight-second and two-second sounds were very easy to distinguish at the beginning, the difference between them diminished more and more in the course of the experiments until the two sounds of 3.62 and 4.42 seconds in length closely resembled each other.
The harder the tasks became, the more the rats decided against taking part in the test, the researchers observed. If they were forced to do so, they provided far more false answers than during voluntary participation. This shows that the animals were able to assess whether they would be up to the task before the start of the test or not. Thus, the brain of a rat and possibly also of other animals have much more complex capabilities than previously thought, the researchers said. The results could now help to better understand thought processes in humans.Allison Foote and Jonathon Crystal (University of Georgia, Athens): Current Biology, Online Pre-Release, DOI: 10.1016 / j.cub.2007.01.061 ddp / science.de? Ilka Lehnen-Beyel advertisement