Small numbers are processed in the right side of the brain, while large numbers are processed in the left side, a new study suggests.
The findings offer new insights into the mystery of how our brains handle numbers, researchers said.
The results could help to tailor rehabilitation techniques for patients who have suffered brain damage, such as stroke patients, and inform treatments for conditions such as dyscalculia, which causes difficulty in processing numbers, they said.
The brain is divided into two halves - the left side controls the right half of the body, and vice versa.
Generally, one side of the brain is more dominant than the other. For example, people who are right-handed tend to have more activity in the left side of their brains, researchers said.
"In our new study, in which we used healthy volunteers, we found the left side processes large numbers, and the right processes small numbers," said Qadeer Arshad from Imperial College London.
"So for instance if you were looking at a clock, the numbers one to six would be processed on the right side of the brain, and six to twelve would be processed on the left," said Arshad.
For the study, researchers temporally deactivated either the left or right side of the brain of healthy volunteers.
They did this using a complex technique - the volunteers were asked to wear goggles that showed them a picture of either a horizontal or vertical line.
At the same time, the participants underwent a procedure called the caloric reflex test. This is commonly used to diagnose ear and balance disorders and involves trickling either hot or cold water into a person's ears.
Volunteers then took a range of number tests. These involved saying the middle number between a number range, for instance between 22 and 76, or drawing the numbers of a clock face.
"When we activated the right side of the brain, the volunteers were saying smaller numbers - for instance if we asked the middle point of 50-100, they were saying 65 instead of 75. But when we activated the left side of the brain, the volunteers were saying numbers above 75," said Arshad.
"If someone was looking at a range of 50-100 then the number 80 will probably be processed on the left side of the brain. However, if they are looking at a range of 50-300, then 80 will now be small number, and processed on the right," he said.
After asking the volunteers to draw a clock face, researchers found that when the right side of the brain was activated, the participants tended to draw the numbers 1 to 6 slightly larger and more prominent, with greater space between the numbers. When the left brain was activated, they drew 6 to 12 bigger.
The findings were published in the journal Cerebral Cortex.
