Quantity matching by an orangutan (Pongo abelii)

Bears ‘count’ too: quantity estimation and comparison in black bears, Ursus americanus

(2012) Jennifer Vonk et al.   ANIMAL BEHAVIOUR

Concept formation in American black bears, Ursus americanus

(2012) Jennifer Vonk et al.   ANIMAL BEHAVIOUR

Putting the elephant back in the herd: elephant relative quantity judgments match those of other species

(2012) Bonnie M. Perdue et al.   ANIMAL COGNITION

Large quantity discrimination by North Island robins (Petroica longipes)

(2012) Alexis Garland et al.   ANIMAL COGNITION

Can angelfish (Pterophyllum scalare) count? Discrimination between different shoal sizes follows Weber’s law

(2010) Luis M. Gómez-Laplaza et al.   ANIMAL COGNITION

Use of Number by Fish

(2009) Christian Agrillo et al.   PLoS One

How the great apes (Pan troglodytes, Pongo pygmaeus, Pan paniscus, Gorilla gorilla) perform on the reversed reward contingency task II: Transfer to new quantities, long-term retention, and the impact of quantity ratios.

(2008) Jana Uher et al.   JOURNAL OF COMPARATIVE PSYCHOLOGY

Monkeys (Macaca mulatta and Cebus apella) track, enumerate, and compare multiple sets of moving items.

(2008) Michael J. Beran   JOURNAL OF EXPERIMENTAL PSYCHOLOGY-ANIMAL LEARNING AND COGNITION