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Bears may be able to estimate and compare numbers of items.
Jennifer Vonk of Oakland University in Rochester, Michigan, and Michael Beran of Georgia State University in Atlanta trained three captive black bears (Ursus americanus) to distinguish between two groups of dots (pictured) displayed on a touch-screen computer. One bear was trained to touch the group containing the most dots, and the others to select the group with the fewest. By varying the size and positions of the dots, researchers tested whether the animals could recognize dot number independently of the total area covered by the dots. Although the bears showed a preference for dots occupying a larger area, they also showed some ability to judge the relative numbers of dots.
The bears' numerical skills may have evolved to help them in complex foraging environments, the authors suggest.