Part I Experimental; Chapter I Sensation and Perception; Chapter II Habit Formation; Chapter III Mental Imagery; Chapter IV Memory; Chapter V Suggestion; chapter VI Reasoning and Knowledge Tests; chapter VII Appreciation Tests; chapter VIII The Effects of Training; Chapter IX Mental Fatigue; Part II Statistical; Chapter X Association; Chapter XI Contingency; Chapter XII Frequency Diagrams; Chapter XIII Averages; Chapter XIV Deviations; Chapter XV Correlation Ratio; Chapter XVI Correlation Coefficient;