Sensory Acuity

As is almost always the case in modern psychology, our considerations start with sensory acuity, although we shall admittedly only touch on this question. This is not because there is little to say due to a lack of material, for there is no field in which the methods of experimental investigation are more numerous than they are here. However, there is also no field in which these methods are as easy to adapt for differential-psychological purposes as they are in the case of sensory perception. There is nothing essential to be changed in the known procedures with which we determine the threshold of stimulation and differentiation for colors and brightness, pitches and volumes, pressure, temperature, the movement of the limbs, visual and haptic acuity, visual evaluation etc. if, instead of using them to prove Weber’s or some other general law, we use them to identify individual deviations between one person and another. Anyone who wants to acquaint oneself with the whole breadth of such investigative possibilities should read the list of tests that Cattell presents at the end of his above-cited work, and which, out of a total number of 50 mental tests, contains 30 relating to the sensory perceptions.