摘要：This work reviewed recent empirical data on the existence of three distinct cognitive and neural systems behind our ability to understand natural numbers. The first system, specific to adult humans only, enables understanding of exact numbers and their flexible application in cardinal, ordinal and nominal number assignments. The second system is present in preverbal infants and in other species. It represents number magnitudes via spatial representation known as a mental number line. Chronometric studies have revealed several phenomena such as the numerical distance and size effects, and the SNARC effect, which point to the conclusion that the meaning of exact numbers is mapped into an evolutionary older system for approximate numerosity, also known as a number sense. The third system enables fast and accurate enumeration or subitisation of small sets of objects. This system is closely related to attention and working memory because it depends on visual indexing or object individuation. It is also present in preverbal infants, as well as in some animal species. Neuroscience research showed that there are partially distinct neuronal circuits for representation of exact numbers, approximate numerosity and enumeration of small sets. At the end of the study, a research on the possible interactions between these three systems was reviewed because it is still an open question to what degree the understanding of the concept of exact number relies on the system for approximate numerosity or the system for fast enumeration.
关键词：numbers; mental number line; number sense; subitisation
