Ants’ Numerosity Ability Defined in Nine Studies

Abstract

The ants Myrmica sabuleti Meinert 1861 can add numbers (as non-symbolic displayed elements) or odors when having perceived them simultaneously. Otherwise, (i.e. having perceived them consecutively), they cannot do so. They can subtract one visual element or an odor when perceiving the result of the subtraction. These ants present a concrete notion of zero when faced to visual or olfactory cues. They locate the zero at the end of a decreasing and at the start of an increasing series of elements, i.e. at its due location. Experimented with smaller and larger numbers, the ants locate the smaller numbers on their left and the larger ones on their right, having thus a mental number line. The ants’ accuracy in discriminating two successive numbers obeys to a logarithmic function of the relative difference between these numbers. Their arrangement of amounts on the number line is thus non-linear but compressed with increasing number magnitude.