Current views of the visual system assume that the primate brainanalyses form and motion along largely independent pathways1;they provide no insight into why form is sometimes interpretedas motion. In a series of psychophysical and electrophysiologicalexperiments in humans and macaques, here we show that someform information is processed in the prototypical motion areasof the superior temporal sulcus (STS). First, we show that STScells respond to dynamic Glass patterns2, which contain nocoherent motion but suggest a path of motion3. Second, weshow that when motion signals conflict with form signalssuggesting a different path of motion, both humans and monkeysperceive motion in a compromised direction. This compromisealso has a correlate in the responses of STS cells, which alter theirdirection preferences in the presence of conflicting impliedmotion information. We conclude that cells in the prototypicalmotion areas in the dorsal visual cortex process formthat impliesmotion. Estimating motion by combining motion cues with formcues may be a strategy to deal with the complexities of motionperception in our natural environment.