Why they work is unclear, but it is most likely related to their visual system. Experts say that "a cow's depth perception is such that it makes little or no distinction between painted stripes on a dark background and bars over a pit." Cattle may acquire the behavior of avoiding grids over pits either from individual experience or through imitation of other cattle. However, painted grids have been reported to work with semi-wild cattle with no prior exposure to virtual grids.