When the walls have two tubes to choose from, one with two flies and the other with three, they touch the tube with three flies. This experiment shows that arrabios can distinguish two small amounts.
However, in tests of more than four objects, the walls failed. That is really striking, because neither children nor monkeys invent in those cases. The number of objects that separate is limited, so it seems that above that amount they are not able to control all objects simultaneously.
However, as for the functioning of the brain, arrabios and children or monkeys do not separate amounts in the same way. Scientists don't know how to separate the arrabios, it can be by volume or because more flies generate more noise.