The fingers
The hand, and more generally the body, has a very important role in children's acquisition of arithmetic.
The child touches everything in order to make acquaintance with the world, and this is done primarily with the hands.
Anthropological studies on primitive peoples reveal that those savages who have not reached the stage of finger counting are almost completely deprived of all perception of number. Such is the case among numerous tribes in Australia, the South Sea Islands, South America, and Africa (see Dantzig).
Traces of the anthropomorphic origin of counting systems can be found in many languages. In the Ali language (Central Africa), for example, "five" and "ten" are respectively moro and mbnuna: mom is actually the word for "hand" and mbouna is a contraction of moro ("five") and bouna, meaning "two"; thus "ten" = "two hands" (see Ifrah).
It is therefore very probable that words for the first ten numbers derive from expressions related to finger-counting. But this is an unverifiable hypothesis, since the original meanings of the names of the numbers have been lost.
In any case the human hand is an extremely serviceable tool and constitutes a kind of "natural instrument" well suited for elementary arithmetic.
In addition, the asymmetric disposition of the fingers puts the hand in harmony with the normal limitation of the human ability to recognise number visually (the famous limit set at four).
If you want to show that a set contains three, five, seven or ten elements, you raise or bend simultaneously three, five, seven or ten fingers. using your hand as cardinal mapping.
The human hand can thus be seen as the simplest and most natural counting machine.
Even today the greater portion of humanity is counting on fingers: the best way of performing the simple calculations of his daily life.
