The number “zero” is central to contemporary mathematics, as well as to our scientifically and technologically advanced culture. Yet, it is a difficult number to truly “understand”. Children grasp the symbolic number “zero” –– long after they start to understand, at ~4 years of age, that “nothing” can be a numerical quantity (i.e. ‘the empty set’), which is a quantity smaller than “one”. Therefore, scientists had assumed that the concept of “nothing”, as a numerical quantity, would be beyond comprehension for any subhuman animal.
Recent studies on cognitively-advanced vertebrates (i.e. animals having a spinal column/backbone) have challenged this view, however. Monkeys and birds can not only distinguish numerical quantities, but can also grasp “the empty set” as the smallest quantity on the mental-number line. Authors [see attached article & editorial] demonstrate that the honey bee –– a small insect on a branch very remote from humans on the animal tree-of-life –– also belongs to “the elite club” of animals that understand “the empty set” as the conceptual precursor of the number “one”.
Authors trained individual honey bees to the numerical concepts of “greater than” versus “fewer than” –– using stimuli containing one, up to six, elemental features. By learning, honey bees were discovered to be able to extrapolate the concept of “less than” to order (in their little bee brains) “zero numerosity” at the lowest end of the numerical continuum (i.e. bees could distinguish that “zero” was less than “one”, less than “two”, less than “three”, less than “four”, less than “five”, and less than “six”). Bees therefore exhibit an understanding that parallels vertebrate animals –– including the African grey parrot, chicken, nonhuman primates, and even preschool children.
Science 8 June 2o18; 360: 1124–1126 & pp 1069–1070 [Editorial}