Our innate ability to sense numerical quantities has been associated with a region of our brain that researchers are referring to as a kind of sixth sense, or "number sense," NPR reports.
A team of scientists from Utrecht University in the Netherlands discovered a small patch of neurons above each ear that allows us to, at a quick glance, determine how many objects are in front of us. For most people, this sense is limited to around five objects, but for some particularly gifted folk, sensed quantities are seemingly limitless.
"When we see a small number of items visually, we don't need to count them," Ben Harvey, lead researcher of the study published yesterday in the journal Science, told NPR. "We just know how many there are straight away. One subject we measured was just beautiful. His brain responds all the way through the number eight."
The region of the brain discovered by the scientists, Harvey explained, lights up when we see a specific quantity, and apparently we aren't the only primates with this unique ability. In previous studies on the subject, it was found that neurons in the brains of monkeys are also activated when a certain number of objects appear in front of them, prompting Harvey and his team to look for similar neurological responses in humans.
Through a series of experiments, Harvey and his team used functional magnetic resonance imaging (fMRI) to measure and map participants' brains while showing them a series of circles on a screen, starting with one circle and leading up to eight circles. A clump of about 80,000 neurons, roughly the size of a postage stamp, lit up in the brains of all eight participants during the study, and the researchers discovered a pattern: "Neurons that sensed the smaller numbers were located on one side of the patch while those that responded to larger numbers were on the other side," according to NPR.
"There are maps on the brain that represent the surface of the skin - or the surface of the retina," Harvey said. "These all reflect an external organ. We found the first map for a cognitive function. For seeing, there's more neurons that process the center of the field vision, where you have very sharp vision. For touch, you have huge hands mapped onto the brain, but smaller ones for legs."
Harvey and his team found that more neurons in the brain are devoted to sensing smaller quantities as opposed to large ones, which might explain why if a number of toothpicks are dropped on the floor, most people would be able to sense five but not 216.
"The idea [of sensing toothpick quantities] is well known because of the movie 'Rain Man', but few such people exist. And we haven't scanned one," Harvey said. "So we don't really know whether they are doing the same task - that is, determining large numbers quickly and accurately, like we all do for small numbers. We would be very excited to meet one of those savants."
Click here to see an image depicting the small patch of neurons in the brain of participants that discerned how many dots they saw on the screen.
