Two apparatus assemblies for the study of real movement

Two forms of apparatus are described for the study of real movement. The first is characterized as a hydraulic system and is used where the S’s rate of movement threshold is to be deter-mined. The basis of the apparatus is a hydraulic cylinder with a piston rod carrying a crosspiece with a visual stimulus attached. The piston-crosspiece assembly is raised,by charging the apparatus with oil, which is then discharged back into a reservoir through a finely tapered adjustable needle valve. Velocity of motion may be regulated by varying the needle valve opening or a mass placed on the piston. The second apparatus is useful for determining the displacement threshold, the minimal distance through which a change of stimulus from one position to another can be perceived. The apparatus consists of a cathode ray display of a linear change of voltage from one value to another. Both total displacement and rate of displacement are adjustable. The S views the cathode ray trace through an optical system designed to minimize perception of extraneous motion.