Ordinality in rats
A central aspect of number cognition refers to an ability to identify a target element in a series of identical elements on the exclusive basis of its ordinal position. Rats are capable of learning to enter a target tunnel, to find a food, solely on the basis of its ordinal position in an array of six or 18 identical tunnels. Their performance was maintained also when the tunnel size and distance between tunnels were changed to prevent animals finding the target tunnel by relying on spatial cues. Interestingly enough, rats remember the ordinal position of the tunnel where they found food after a year!
Related scientific publications
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Suzuki K, Kobayashi T. 2000 Numerical competence in rats (Rattus norvegicus): Davis and Bradford (1986) extended. J. Comp. Psychol. 114, 73–85. (doi:10.1037/0735-7036.114.1.73)