The apparent persistence of seen movement in a homogeneous visual field (Ganzfeld) is described. The task required that the subject observe the movement of a single, black, spherical stimulus in an otherwise empty field and to report when its movement ceased. The time interval between real and apparent cessation of movement was defined as “time delay.” The hypothesis advanced states that the apparent speed of the stimulus in the Ganzfeld is dependent upon the square of its real velocity, its duration and its size. This may be expressed as t=r+(1/av2) where t=time delay, r=reaction time, v=velocity, and a=the constant of inverse proportionality. The data are discussed in terms of “contrast of velocity.” The notion here is that a stimulus traveling at high speed and for a relatively long duration produces a more definite perception of velocity than one traveling slowly and observed for a shorter period of time. Therefore, when the former stimulus suddenly is stopped, the resulting contrast of velocity is great and the response to it rapid, whereas when the latter stimulus is similarly stopped, the resulting contrast of velocity is slight and its perception therefore slower. The data were shown to support this hypothesis.
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