Why Do Our Brains "See" Or Perceive Smaller Numbers Better?

 

Have you ever wondered why it is easier to guess the correct number of items in a bottle if there are fewer items?  Or why you might remember smaller numbers you've seen on posters than the larger numbers?  Well back in the 1870's, Willam Stanley Jevons wondered about the number 4.  He noted that if he tossed a handful of black beans into a box and fleetingly glanced at them, he was more likely to remember the number of beans if there were 4 or less.  If there were 5 or more beans, his guesses were more frequently wrong.

The article he published in 1871, lead to a long debate on why there is a limit on the number of items in a set that we can accurately remember. Recently, a new study was published which takes us a step closer to understanding why 4 seems to be the limit.

Apparently, the brain uses two mechanisms in order to judge the number of objects it sees.  The first mechanism is used to estimate quantities while the other improves the accuracy of those estimates but only for small numbers. This study connects debated ideas with the neural underpinnings.  This is a huge step because there is little out there in cognition where scientists have been able to connect with biological foundations. 

This study does not finish the debate or fully answer the question but it does begin to untangle the biological underpinnings for how the brain is able to judge numbers. The understanding of how the brain judges quantities could help solve bigger questions about memory, attention, and mathematics.  It turns out that the brains ability to judge the number of items in a set has nothing to do with counting. It's a number sense people are born with as demonstrated by infants and other animals such as fish, monkeys, bees.  

This innate number sense is often associated with survival for animals because they have to judge how much food, how much competition, where the most flowers are.  Since more than just humans have this ability, it is thought that innate number senses has been around for a very long time. 

In 2002, a paper was published that was able to link numbers to specific neurons. The authors studied monkeys and found that numbers are linked to neurons in the prefrontal cortex where higher level processing takes place.  These neurons lit up on a brain scan when the brains preferred number was seen. So if the brains favorite number is 3, the neurons fire more when the brain sees three objects.  In others, the number might be 5. It was also discovered that the neurons fire for the numbers next to the favorite number but do so less often.

Ten years later, in 2012, these same researchers discovered that these neurons respond when they are estimating a set of sounds or visual items that correspond to their favorite number. Unfortunately, no one had been able to find these neurons in the human brain due to brain imaging tools which did not have the resolution to study individual neurons and most scientists are unwilling to put individual electrodes deep into the brain.

Later, the same group in conjunction with a group in Germany were able to use people who already had the electrodes planted in their brains and discovered humans appear to have neurons that fire with the preferred numbers and in a later study, they analyzed additional firings to discover that for items above the number 4, the neurons fired less precisely than they did for numbers below 4. 

These findings align with the idea that the brain can only hold a limited number of items in their working memory which is 4. It may be the mechanisms are connected but there will have to be more research to investigate both the firing of the neurons and the number of items humans can hold in their working memory.  This is just the beginning of learning more about this area and will have to be explored in more detail.

Let me know what you think, I'd love to hear.  Have a great day.