Domestic dogs show flexible left-to-right spatial-numerical association

<title>Abstract</title> <p>The Spatial Numerical Association (SNA) is a form of spatial representation of numerosities, which associates small numerosities with the left and large ones with the right. SNA has been reported across phylogenetically distant species, suggesting that its biological origin is independent of language, education, and symbolic number systems. However, research on SNA in domesticated mammals remains sparse. Here, we investigated SNA in domestic dogs, a domesticated mammal characterized by heterogeneous individual experiences and prolonged interactions with humans. We trained 49 pet dogs to circumnavigate a central panel displaying eight dots. Then, in an unrewarded test, they were presented with two identical lateral panels displaying either a smaller (4) or a larger (16) numerosity. To account for individual lateralization, dogs were classified as SNA-consistent only if they chose the left panel in the smaller test and the right panel in the larger test. The number of dogs showing flexible SNA-consistent responses exceeded chance expectations and persisted when continuous variables (perimeter, density and area) were unreliable. To assess whether SNA correlated with performance in a visual numerical discrimination task, some dogs also underwent comparisons between numerosities ranging from 4 to 16. Remarkably, dogs showing a consistent SNA outperformed the others in the discrimination with more difficult ratio (&gt; 0.70). Our results show a left-to-right-oriented SNA in adult dogs, suggesting that numerical spatialization in non-human animals persists despite potentially extensive differences in individual experience and may be related to the efficiency of the Number Sense.</p>