Measurement of temperamental or personality factors is still the most difficult of all of the fields, although several relatively new approaches are being tried. In one of these approaches the individual is put under conditions of mental stress in a controlled condition designed to produce frustration. Evidences of emotional instability and quickness of recovery are studied to determine whether these samples of emotional behaviour will be predictive of behaviour under stress situations in civilian or military life. Another approach is that of attempting to relate factors of temperament to constitutional differences in body builds. Here the old fallacy of attempting to distinguish sharp body types has been overcome by recognizing the need for a quantitative method of describing the test profile resulting from measurements on a number of body dimensions. In this way gradations in body build are recognized.