Suppose two friends want to arrange an appointment to meet in several days' time. They present each other with threads which have the same number of knots and as many knots as there are days to elapse before the meeting. Every day at sunrise each of them unties one of the knots. When at length there are no knots left they know that the appointed day has arrived.
It is very curious that the Moï, whose recollection of facts is almost infallible, are unable to recall either figures or dates without the assistance of mechanical aids to memory.
Doctor Noël Bernard, of the Colonial Forces, tells a very interesting story in his exhaustive monograph on the Kha.
"In a village situated in the plateau of Boloven I found the inhabitants stricken with terror. They informed me that a malevolent Genius had been enraged with them for more than a year and was decimating the population. To remedy their ill-fortune they rebuilt the village in a new place, and the death-rate decreased. I happened to ask them the number of the victims in that fatal year. They could not tell me. I renewed the question and the village chief gave me the figures in a highly novel manner. As he called out each victim by name he laid a small stick down at his feet. When the counting was completed the old man summed up as follows: 'Two died during seed time, three during harvest, four at the beginning of the rains,' and so on, concluding with a tragic, 'What a number!' But not a single native present could calculate that number, though there were only thirteen sticks at the feet of the incompetent arithmeticians!"
M. A. Gaultier de Claubry, when he was Director of Public Instruction in Indo-China, had opportunities of making observations which throw light on the incident just related. He used to teach French to twenty-two natives between the ages of twelve and twenty and wished to follow the ordinary rational method of explaining the meaning of a lesson first and asking his pupils to learn it by heart only after that meaning had become clear in their minds.
After a period devoted to repeated attempts along these lines he had to confess himself beaten and that the method was impracticable so far as these particular scholars were concerned, for the more clearly they grasped the meaning of the words the greater was their difficulty in committing them to memory.
Contrary to all the recognized precepts of sound teaching, the Professor resolved to reverse the process, make his pupils first learn the lesson by heart and only proceed to its translation and explanation when they could recite the words without a slip. The results were even more unexpected, for the more quick and certain their memories became the greater was their difficulty in understanding the meaning of the words.
The Professor repeated this experiment from time to time and the same phenomena always recurred.
It seems, therefore, clearly arguable that in certain individual cases connection between the thinking and memorizing faculties is either missing or only imperfectly established. They seem unable to perform their functions simultaneously. The memory cannot work properly unless all other mental processes are suspended.
But to return to arithmetic, the custom of employing pieces of wood to assist calculation is to be found everywhere in the savage world. Our coolies were collected from many different quarters, but they all carried a bamboo in which each evening they cut a notch to reckon up the number of days of service. On pay days they lined up solemnly side by side and each produced his stick from his loin-cloth and presented it for inspection. It was very rarely that our accountants found any error in the number of the notches.