The existence of discrete number sense in rats has been confirmed by research co-led by neuroscientists Professor Yung Wing-ho from City University of Hong Kong (CityUHK) and Professor Ke Ya from The Chinese University of Hong Kong (CUHK) Faculty of Medicine (CU Medicine). This finding offers a critical animal model for examining the neural basis of numerical ability and disability in humans.

The research team has devised a novel approach that settles the long-running debate over whether rats have a sense of numbers. It combines brain manipulation techniques, artificial intelligence modeling, and a novel numerical learning task.

The research clarifies the workings of the mechanisms that underlie numerical ability. The study has been published in Science Advances, a prestigious multidisciplinary scientific journal.

Number Sense Closely Linked to Survival and Intelligence

An essential skill for animals to perceive their environment and one that improves their chances of survival is number sense. It is also a crucial cognitive skill essential to mathematical aptitude, a quality distinguishing intelligent people.

A deficit in number sense is one of the main symptoms of dyscalculia, a learning disability that affects the ability of individuals to learn arithmetic and mathematics. It affects between 3% and 7% of the population.

Number sense is not the same as associated magnitudes, which are continuous dimensions inherent in a set of objects, like the area of visual objects or the duration of sound pulses. Rather, number sense is the ability to compare, estimate, and manipulate non-symbolic numerical quantities.

It has been disputed whether number sense can be evaluated independently of the impact of continuous magnitudes. There has also been a lively debate about which sense is more fundamental, the sense of magnitude or the sense of number.

Study Confirms That the Rat Brain has a Specific Area for Dealing with Numbers

The research team carefully analyzed the data through quantitative analysis, minimizing the impact of continuous magnitudes in numerical tests to ascertain the relative contributions of numbers and magnitudes.

To minimize other distracting factors and maximize the ability of animals to concentrate solely on numbers, they developed an algorithm. This will enable scientists to comprehend how animals interpret and calculate numbers on a deeper level.

According to the study, when trained with sounds that corresponded to two or three numbers, rats with no prior experience with numbers could acquire a sense of numbers. When selecting food rewards, the rats consistently paid attention to the number of sounds, even in the presence of continuous magnitudes.

Our study helps dissect the relationship between magnitude and numerosity processing. We discovered that when we blocked a specific part of the rats’ brain, called the posterior parietal cortex, their ability to understand numbers was affected but not their sense of magnitude. This suggests that the brain has a specific area for dealing with numbers. In fact, this is the first time scientists have demonstrated that rats have the ability to discriminate and categorize three different numbers in a single test, surpassing a simple quantity comparison.”

Yung Wing-ho, Professor and Associate Dean, Jockey Club College of Veterinary Medicine and Life Sciences

Yung Wing-ho is the Chair Professor of Cognitive Neuroscience at CityUHK.

Professor Ke from the School of Biomedical Sciences at CU Medicine expressed excitement about the findings.

Professor Ke adds, “The study not only solves a long-standing mystery about how brains handle numbers, but also offers new insights into studying the specific neural circuits involved in number processing in animals and how genes are associated with mathematical ability. Furthermore, the findings from neural network modeling could have practical applications in the field of artificial intelligence. In the future, our increased understanding of the brain mechanisms underlying the processing of numbers may contribute to the development of interventions for individuals with numerical difficulties.”