Left-to-right spatial-numerical association in domestic dogs

The Spatial Numerical Association (SNA) refers to a spatial representation where smaller numerosities are linked to the left and larger ones with the right. SNA has been documented in humans, infants, primates, chicks, and even insects, supporting the idea that it is biologically rooted, rather than dependent on education or symbolic number systems. Domestic dogs offer a valuable model for cognitive research due to both their accessibility as subjects, given the possibility to involve large samples of pet dogs, and to their inter-individual variability in their life experiences. Studying the SNA in dogs therefore provides a unique opportunity to test whether such numerical spatialization is robust to experiential heterogeneity. In the present study, we investigated the potential presence of bilateral SNA in eighteen domestic dogs, tested in a spontaneous choice task. After ten exposures to a reference numerosity depicting 8 dots, dogs underwent two test trials in which lateral panels displayed either fewer (4) or more (16) dots than the reference numerosity. About 70% of the dogs chose the left panel when presented with fewer-than-reference stimuli and the right panel when presented with more-than-reference stimuli. These results support the presence of a left-to-right oriented SNA in adult dogs, suggesting that numerical spatialization in non-human animals exists despite potentially extensive differences in individual experience.