The maze has since been used extensively by researchers interested in studying the spatial learning and spatial memory of animals. For example, Olton and colleagues found that performance declined only slightly to 82% novel entries in the first 17 entries on a 17-arm maze. Roberts found no decline in the percentage of correct choices as the number of arms on a radial maze were increased from 8 to 16 and then to 24. Cole and Chappell-Stephenson, using a radial maze with food locations ranging from 8 to 48, estimated the limit of spatial memory in rats to be between 24 and 32 locations.