Smooth pursuit consists of conjugate eye movements that allow both eyes to smoothly track a slowly moving object so that its image is kept on the foveae. For example, smooth pursuit eye movements are used when you track a child on a swing. Only animals with foveae make smooth pursuit eye movements. Rabbits, for instance, do not have foveae, and their eyes cannot track a small moving target. However, if a rabbit is placed inside a rotating drum painted on the inside with stripes so that the rabbit sees the entire visual field rotating en bloc, it will track the stripes optokinetically. Humans have both smooth pursuit and optokinetic eye movements, but pursuit predominates. When you track a small, moving object against a detailed stationary background, such as a bird flying against a background of leaves, the optokinetic system will try to hold your gaze on the stationary background, but it is overridden by pursuit. Pursuit works well at speeds up to about 70°/sec, but top athletes may generate pursuit as fast as 130°/sec. Pursuit responds slowly to unexpected changes—it takes about 100 msec to track a target that starts to move suddenly, and this is why we need the faster acting vestibulo-ocular reflex (VOR) to stabilize our eyes when our heads move. However, pursuit can detect patterns of motion and respond to predictable target motion in much less than 100 msec. Pursuit cannot be generated voluntarily without a suitable target. If you try to pursue an imaginary target moving across your visual field, you will make a series of saccades instead of pursuit. However, the target that evokes pursuit does not have to be visual; it may be auditory (e.g., a moving, beeping pager), proprioceptive (e.g., tracking your outstretched finger in the dark), tactile (e.g., an ant crawling on your arm in the dark), or cognitive (e.g., tracking a stroboscopic motion in which a series of light flashes in sequence, even though no actual motion occurs.