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Six tree shrews and 8 rats were tested for their ability to infer transitively in a spatial discrimination task. The apparatus was a semicircular radial-arm maze with 8 arms labeled A through H. In Experiment 1, the animals were first trained in sequence on 4 discriminations to enter 1 of the paired adjacent arms, AB, BC, CD, and DE, with right (or left, for half the animals) symbols signifying positive options; then they were tested with the previously unused pair of arms, FH. All tree shrews and 4 rats transitively chose H (or F for half the animals). In Experiment 2, all tree shrews and 5 rats transitively chose H (or F) on 3-option tests of FGH. The results suggest that these animals used transitive relation in solving novel problems.