If someone holds up three fingers, you’ll instantly notice that it’s three. However, if someone places several oranges in front of you, let’s say more than five, what would your estimation be?
You’ll probably just use terms like ‘half-a-dozen’ and ‘umpteen’.
That’s a phenomenon called subitising, as Dubai-based neuro-psychiatrist Madiha Khan explains. When we’re confronted with five or more items, our estimation becomes more confused and imprecise.
“Subitising refers to the idea of perceiving the number of a small group of items at a glance, without actually counting them,” she explains. It can be perceptual, which means the ability to identify or visually perceive the number of a group of items. It could also be conceptual, which means knowing the number by understanding a specific pattern of arrangement. For instance, a child rolls a pair of dice and knows there are five dots because they see a two and a three.
Subitising refers to the idea of perceiving the number of a small group of items at a glance, without actually counting them. It can be perceptual, which means the ability to identify or visually perceive the number of a group of items. It could also be conceptual, which means knowing the number by understanding a specific pattern of arrangement....
Children are taught and trained in subitising in the early years, where they develop a cohesive understanding of numbers up to ten. It is a crucial skill for children to develop in their early years, as they gain a clearer idea of how a number is made.
There are specific neurons involved in subitising and counting. The neural mechanisms for perceiving each number, less than five, are sharper and accurate. However, the neurons have a less accurate processing method, when used for larger numbers.
Estimation vs subitising
What if someone showed you a photo of a family gathering with around four people? You might not have enough time to count, but you will instantly answer, four. However, if you’re shown a photo of a family gathering and asked to make an assumption. You’re slightly hesitant: You’ll answer seven. The correct answer is eight, but close enough.
This form of subitising with regard to small numbers, changes when there are five elements or more. According to a recent 2023 study Distinct neuronal representation of small and large numbers in the human medial temporal lobe published in the international journal, Nature Human Behaviour, research groups involved in the project were able to demonstrate some years ago that the brain has nerve cells responsible for each number till ten.
Some neurons fire, for example, primarily for two elements, other for four elements and again others for seven elements, as explained by international Neuroscience News magazine.
However, as the lead researcher explained, the neurons fire in response to slight variations in the number. The brain cell for “seven” elements also fires for six and eight elements, but less robustly. The same cell is still activated, but even less so for five or nine elements.
On the other hand, when a brain cell for a number of three things fires, it restricts the brain cells for the numbers two and four. This reduces the risk that these cells could incorrectly fire for the number three, explains the study. This mechanism does not exist for the neurons activated for numbers five, six, or eight. As a result, there’s a higher error rate for these numbers.
Experiments to understand the neural basis of subitising
In the 2023 study Distinct neuronal representation of small and large numbers in the human medial temporal lobe published in the international journal, Nature Human Behaviour, the researchers recruited 17 patients at the University Hospital Bonn, Germany, preparing for brain surgery to treat epilepsy. As part of their treatment, the patients had microelectrodes inserted into their brain.
"We were able to use them to measure the reaction of individual nerve cells to visual stimuli,” Esther Kutter, a German PhD student in the research group, had explained in the study.
The participants watched a computer screen, which displayed varying numbers of dots for half of a second. After this glimpse, researchers asked the subjects whether they had seen an odd or even number of dots. The subjects answered quickly and accurately for up to four dots, the study found, making practically no mistakes.
Once there were five or more dots, however, both errors and response time began to grow along with the number of dots. The research produced novel and intriguing mechanics of the human brain, revealing new details how we process numbers. It also explains, to some measure, why some people struggle with numbers, based on the firing of the neurons – but more work is needed, especially in understanding dyscalculia, which is a developmental disorder, associated with a poor grasp of numbers and number-related concepts.
When does it become dyscalculia?
When someone says “I’m bad at writing and reading”, there’s an instant flurry of worry. It could mean dyslexia. However, when a person says “I’m bad at math”, they’ll probably find a fellow support group who have a shared hatred of the subject.
However, this sometimes could indicate dyscalculia, which is not often diagnosed, explains Rachel Tyson, Dubai-based neurologist. It’s not a simple matter of “just being bad at math”. A person who has dyscalculia is not able to subitise, even very small quantities.
Explaining further, Khan says, "Developmental dyscalculia is a learning disability that interferes with normal acquisition of arithmetical skills. People who are affected by it, show persistent difficulties in number processing, which are associated with changes in brain structure and function," she says. Khan adds that research also shows reduced grey matter in the parietal cortex, including the intraparietal sulcus, the areas of the brain that play a part in quantifying numbers. Other areas of the brain that are affected, include the frontal and occipito-temporal areas.
These structural differences in the brains of individuals with developmental dyscalculia cause long term problems with mathematic skills and number processing which can limit these individuals in their educational and professional endeavors.
While subitizing is one of the core deficits in dyscalculia, it’s considered as a pre-math skill that is very important and enables us partially to spatially recognize numbers in our minds....
They would have difficulty just subitising three elements. They would not be able to identify numeral quantities, and see which one is larger. Their number sense would be poor, which indicates that they would be unable to break up numbers that can be joined together. Moreover, they would find it difficult to make connections and predictions in math. However, it does not indicate difficulties in cognitive abilities, or spatial reasoning.
“When a child is unable to tell how many objects are there in a small group, that’s a sign that they might have dyscalculia. This disorder often goes undiagnosed for a long time, as parents tend to think that children will ‘master’ math as they grow up,” adds Tyson. On the other hand, mathematical disabilities can also be the consequence of brain injury.
While subitizing is one of the core deficits in dyscalculia, it’s considered as a pre-math skill that is very important and enables us partially to spatially recognize numbers in our minds, adds Carla Khalil, a Dubai-based neuropsychologist. "Luckily, evidence shows us that it’s a skill that we can also now train just like we train visual spatial abilities, the ability to recognize, remember, and mentally analyse and manipulate visually presented information."