[Measuring mental performance: an old idea and a new approach]

First results are reported from the attempt to make mental performance measurable in terms of elementary thought processes. The formation of order in thought is seen as a unit with which mental performance can be measured. The formation of order is described by complexity-reducing structuring. A measurement process for elementary problem-solving demands based on the symbol-distance effect was also developed. From the comparison with the solution of complex problems, it was shown that those test subjects who attain the best solutions to more complex demands are also those who have the most parsimonious cognitive structures in problem solving. Complexity reduction is measured by the performance of the alpha band in EEG mapping. With the use of a more parsimonious cognitive structure, higher performance is measured in comparison with the use of complexity-intensive cognitive structure.