Can animals count? Neuroscientists resolve long-standing debate

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) collaborated to make a groundbreaking discovery about number sense in animals by confirming the existence of discrete number sense in rats, providing a critical animal model for investigating the neural basis of numerical ability and disability in humans.

The research team has devised a pioneering method that utilizes a unique numerical learning problem, brain manipulation techniques, and artificial intelligence modeling. This method effectively settles a long-standing debate on whether rats possess a numerical sense. The study elucidates the mechanisms that underlie numerical aptitude.

Number sense closely linked to survival and intelligence

Numerical cognition is a crucial capacity in animals' observation of the environment and enhances their likelihood of survival. Furthermore, it is a crucial cognitive skill that is essential for mathematical proficiency, a distinguishing characteristic of human intellect. Dyscalculia is a learning disability that impacts the acquisition of arithmetic and mathematics skills in individuals with normal intelligence. Approximately 3% to 7% of the population are affected by this condition, which is characterized by a deficiency in number sense.

Number sense is the ability to compare, estimate, and manage numerical quantities that are not represented by symbols. It focuses on the inherent dimensions of a set of items, such as the area of visual objects or the duration of sound pulses, rather than their related magnitudes. There have been debates on whether it is possible to evaluate number sense without considering the impact of continuous magnitudes. Furthermore, there is a lively and ongoing discussion concerning whether the perception of magnitude or the perception of number is more basic.

Study confirms the rat brain has a special area for dealing with numbers

The research team reduced the impact of continuous magnitudes in numerical tests and performed thorough quantitative analysis in the study to ascertain the individual contributions of numbers and magnitudes. An algorithm was created to provide stimuli that allow animals to concentrate solely on numbers, while minimizing other sources of distraction. This research will enhance scientists' comprehension of animals' perception and quantification of numbers.

The study revealed that rats lacking prior numerical knowledge were capable of acquiring a numerical sense through training with auditory stimuli representing two or three numbers. Although continuous magnitudes had an impact, the rats consistently prioritized the quantity of sounds when selecting food rewards.

Professor Yung, who is the Associate Dean of the Jockey Club College of Veterinary Medicine and Life Sciences and also holds the position of Chair Professor of Cognitive Neuroscience at CityUHK, stated that our study contributes to the analysis of the connection between the processing of magnitude and numerosity. Our findings indicate that inhibiting the posterior parietal cortex, a specific region of the rats' brain, resulted in a disruption of their numerical comprehension while leaving their perception of magnitude unaffected. These findings indicate that the brain possesses a distinct region dedicated to processing numerical information. Scientists have just shown, for the first time, that rats possess the capacity to differentiate and classify three distinct numbers in a single experiment, thereby exceeding a basic comparison of quantities.

Professor Ke, a faculty member of the School of Biomedical Sciences at CU Medicine, expressed enthusiasm regarding the discoveries. "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," she said. "Furthermore, the findings from neural network modelling 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."

Journal Reference: Tuo Liang, Rong-Chao Peng, Kang-Lin Rong, Jia-Xin Li, Ya Ke, Wing-Ho Yung. Disparate processing of numerosity and associated continuous magnitudes in rats. Science Advances, 2024; 10 (8) DOI: 10.1126/sciadv.adj2566