Human motion perception is assumed to be functionally described by an array of bi-local detectors feeding later, higher order computational stages. Using this model as a guide, improvement of spatio-temporal displacement sensitivity by temporal integration (summation) was measured in human central vision using random dot pattern apparent-motion stimuli. Our results agree with previous experiments with regard to improvement of maximum perceivable spatial displacement but show that contrary to previous results the minimum perceivable spatial displacement can be improved in a similar manner. Furthermore, stimulus duration is a more accurate predictor of sensitivity than the number of frames in the stimulus over a wide range of stimulus parameter values. Finally, our results indicate that temporal tuning of motion detectors is inversely related to the size of the spatial pattern displacement.