We predict that velocity thresholds for objects moving a certain amplitude covary with peak velocities of saccades of the same amplitude, as these eye movements cause comparable intra-saccadic speeds of objects on the retina. Specifically, we predict: 1) Peak velocity of saccades increases with saccade amplitude (main sequence). 2) Peak velocity of saccades varies as a function of saccade direction. 3) On average, horizontal saccades have higher peak velocities than vertical saccades, and upward saccades have higher peak velocities than downward saccades. 4) Observers' speed threshold for rapidly moving objects (the point at which the motion trajectory becomes invisible) decreases with the amplitude of the movement; they can perceive higher speeds for longer movement trajectories. 5) Observers' speed thresholds vary as a function of of the object's movement direction. 6) On average, observers' speed threshold is lower for horizontal than for vertical object movements, and lower for downward than for upward object movements. 7) An individual's speed threshold for a given movement vector can be predicted by the same individual's average peak velocity of saccades in the opposite direction. 8) Individuals with slower saccadic speeds are less sensitive to high speeds than individuals with high saccadic peak velocities. If we can obtain sufficient data to estimate the variability in saccadic peak velocities for any given saccade vector, we will also explore if that variability is related to the variability in the threshold (slope of the psychometric function) in the perceptual data.