[Effect of caffeine on motor reactions and visual-mental processing time].

The effect of coffee without and with caffeine (200 mg) on the performance of "awake" respectively "fatigued" subjects was proved. 5 females and 7 males (22 to 32 years) were chosen for the cross-over double-blind study. Motor reaction time, visual-mental processing time, reading-speed and reading-errors were recorded. Further experiments under aggravated conditions were carried out. In the morning ("awake") caffeine increases the efficiency of all parameters excepted the reading errors. At night ("fatigued") the increase by caffeine is insignificant. Even in some subjects caffeine decreases the speed of reading and increases the number of errors. Under test-conditions, which were aggravated by strong acoustical disturbance, caffeine does not improve efficiency, compared with caffeine-free coffee. Overriding into the range of decreasing performance in spite of increasing central activity was not found under any test-condition.