{"fact":"Unlike trained crows that excel at comparing large quantities, untrained crows struggle when both options exceed four items, suggesting training enhances their number sense.","context":"However, the crows failed to discriminate the larger quantity when both sets were greater than four (as in 6 versus 8, 8 versus 12 and 12 versus 16). These results indicate that jungle crows have difficulty discriminating larger amounts, even if they are of the same ratio as that of smaller sets. … crows appear to discriminate between two large quantities better when trained than when untrained.","source":"Bezawork Afework Bogale; Masato Aoyama; Shoei Sugita, Spontaneous discrimination of food quantities in the jungle crow, Corvus macrorhynchos\n, 10.1016/j.anbehav.2014.05.012","index":407}