It was examined if animals can learn to perform bar-pressing only within a determined period of time by the aid of light and tone signals. 6 male BDE-rats (70 days old at the beginning of the experiments) were trained in a modified test chamber to press a bar only in 2h/day (experimental subjects 1 and 2: 13.00–15.00 h; 3 and 4: 15.00–17.00 h; 5 and 6: 24.00–2.00 h). During this time light and tone signals were given and only during this time bar-pressing was rewarded. At the end of the training period all 6 rats showed a change of behavior according to the task, that means: at least 90% of the whole bar pressing activity fell into the determined period of time. Under test conditions the maintenance of this behavior was less stable.