Scientists have discovered the part of the brain responsible for assessing numbers and found that it is laid out topographically so that its nerve cells have the shortest routes to communicate with one another.
Topographical layouts like this are usually associated with the primary senses such as sight, hearing, taste, touch and smell so this suggests that the ability to compare the amount of things – whether grains of sand on a beach of the number of bottles behind a bar – is also a basic “sense”.
“We use symbolic numbers to represent numerosity and other aspects of magnitude, but the symbol itself is only a representation,” said Benjamin Harvey of Utrecht University, who carried out the research published in the journal Science.
Assessing the quantity of something depends on processing visual information from the eye to the brain, while counting with numbers is about recognising the symbols and linking them to a designated quantity.
“This latter task relies on very different parts of the brain that specialize in written and spoken language,” Dr Harvey said.
The study involved asking volunteers to analyse a varying patterns of dots on a computer screen while attached of a functional magnetic resonance brain scanner, which could identify which parts of the brain were active in the task – revealing the involvement of the brain’s outer cortex.
“Every individual brain is a complex and very different system. I was very surprised then that the map we report is in such a consistent location between our subjects, and that numerosity preferences always increased in the same direction along the cortex,” Dr Harvey said.