Scientists have found that the middle finger has a slower reaction time than our thumb or finger because it is inhibited by its central position.
Each part of the body has its own nerve cell area in the brain - we therefore have a map of our bodies in our heads. The functional significance of these maps is largely unclear. What effects they can have is now shown by RUB neuroscientists through reaction time measurements combined with learning experiments and "computational modelling".
They have been able to demonstrate that inhibitory influences of neighbouring "finger nerve cells" affect the reaction time of a finger. The fingers on the outside - the thumb and little finger - therefore react faster than the middle finger, which is exposed to the "cross fire" of two neighbours on each side.
Researchers in a working group led by Dr Hubert Dinse of the Neural Plasticity Lab at the Institute for Neuroral Computation had set subjects a simple task to measure the speed of decision: they showed them an image on a monitor that represented all ten fingers.
If one of the fingers was marked, the subjects were to press a corresponding key as quickly as possible with that finger. The thumb and little finger were the fastest and the middle finger was the slowest.
"You might think that this has anatomical reasons or depends on the exercise... but we were able to rule that out through further tests," said Dr Dinse
"In principle, each finger is able to react equally quickly. Only in the selection task, the middle finger is at a distinct disadvantage," he said.
The report of the working group led by Dr Dinse is published in the current issue of PNAS.