The consequences of Clever Hans’ story upon the investigation of animal numerical comprehension

When it was demonstrated that Hans’ mathematical calculations were due to an artifact, unintentionally given from his trainer, beliefs on animal numerical capacities plummeted. For a long time, all mathematical calculations were believed to be firmly related to language and therefore to symbols. As a consequence, all creatures unable to use language and symbols, mainly pre-verbal infants and animals, were considered unable to reach any numerical comprehension. Such skepticism lasted for a long time, and the lack of studies on animal numerical cognition in the first half of the twentieth century is a consequence of the ‘unfortunate’ Clever Hans’ story. Luckily in the last three decades, interest in animal numerical cognition increased and now a series of numerical abilities, that range from numerical discrimination, ordinal abilities and also arithmetic calculation have all been documented in a large variety of animals.

Related scientific publications

Pfungst, O. (1907). Der Kluge Hans. Ein Beitrag zur nichtverbalen Kommunikation. Frankfurter Fachbuchhandlung für Psychologie, Frankfurt am Main.

Rugani R. (2017). Towards numerical cognition’s origin: insights from day-old domestic chicks. Phil. Trans. R. Soc. B 373: 20160509.

Vallortigara, G., Chiandetti, C., Sovrano, V. A., Rugani, R., and Regolin, L. (2010a). Animal cognition. Wiley Interdisciplinary Reviews. Cogn. Sci. 1, 882–893. doi: 10.1002/wcs.75

Vallortigara, G., Regolin, L., Chiandetti, C., and Rugani, R. (2010b). Rudiments of mind: number and space cognition in animals. Comp. Cogn. Behav. Rev. 5, 78–99. doi: 10.3819/ccbr.2010.50004