Mental abilities are labeled with terms such as memory & problem solving and corresponding performance measures (recall score, # correct) can be obtained. The quantitative EEG (QEEG) measure of brain functioning reflects the electrophysiology of the gray & white matter of the brain underlying the scalp. A database of clinical and non-clinical participants underwent a cognitive activation QEEG to determine the relations between the QEEG measures and cognitive performance for memory (auditory and reading) and problem solving. The analysis revealed correlative (positive and negative) relationships between cognitive performance and the Quantitative EEG (QEEG) measures (coherence, phase, magnitude, etc.) during these cognitive activation conditions. An individual can undergo an evaluation and the subjects values on the relevant (and all) variables can be determined. The deficient QEEG variables can be effectively changed with an operant biofeedback conditioning methodology called EEG biofeedback. The method has been shown to improve memory functioning.