A Brief Chronology of Mental Chronometry. Chronometric Terminology and Paradigms. RT as a Function of Experimental Conditions. The Measurement of Chronometric Variables. Chronometry of Mental Development. Chronometry of Cognitive Aging. The Heritability of Chronometric Variables. The Factor Structure of RT in ECTs. Correlated Chronometric and Psychometric Variables. Sensory Intake Speed and Inspection Time. Theory of the Correlation Between Response Time and Intelligence. The Relation of RT to Other Psychological Variables. Clinical and Medical Uses of Chronometry. The Standardization of Chronometry.