Abstract
Do humans and nonhumans share numerical and perceptual abilities? Some researchers argue that nonhumans, lacking human language, possess exact understanding only of quantities up to about 4. Animals trained in human communication systems might, however, be more advanced. ALEX, a Grey parrot, could, for example, quantify sets of ≤8 items (including heterogeneous subsets) using vocal English labels, comprehend these labels fully, sum small quantities, and had a zero-like concept. He understood number symbols as abstract representations of real-world collections, in ways comparing favorably to those of apes and young human children. He appeared to learn in ways more similar to humans than apes.
