Abstract: Spatial representation of numbers is an important way for human beings to represent numbers. There is a renowned phenomenon named mental number line – small numbers are represented on the left side of the mental number line and large numbers are represented on the right side of the line. Similarly number-form synesthesia is a remarkable phenomenon in which numbers could be perceived consciously and automatically as exist in spatial-defined locations. There are intriguing differences and similarities both on the cognitive processes and on the mechanism of brain. Number-form synesthesia is a kind of explicit, involuntary number-spatial connection which automatically activated by number. While mental number line is implicit, flexible, number-spatial connection which depends on spatial demands of tasks. On the aspect of brain mechanism, synaesthetes were thought to be genetically predisposed to develop such spatial-number association through the random profusion of cortical pathways between brain areas responsible for numerical concepts and those that process spatial representations. However, we assert that these differences are concealed in different levels of awareness (and not in qualitatively different mechanisms). And the study of number-form synesthesia already supplied plenty of substantial data to solve the questions in the domain of spatial representation of numbers, such as the origin of spatial representation of numbers and the representation of double-digit numbers. The study of number-form synesthetes is bound to supply substantial behavior and brain mechanism data to solve the problems existing in the domain of spatial representation of numbers and contribute to reinforce our understanding of human spatial representation of numbers, and it is also able to provide new inspirations to further develop this field of study, which makes it a compelling new approach of this field of study.

Key words: spatial representation of number, number-form synesthesia, mental number line, cognitive process, neural mechanism

摘要： 数字空间表征是人类对数字进行表征的重要方式。数形联觉（number-form synesthesia）是一种数字可以有意识地引起空间知觉的独特现象，与此类似的是非联觉者中广泛存在的无意识的心理数字线（mental number line）现象。两者在行为和脑机制上存在着很多重叠，也存在着值得思考的差异。数形联觉的研究能够提供实质性的行为和脑机制数据，用以解决数字空间表征研究中出现的问题，加强对于数字空间表征的理解；也为更加全面深入地开展进一步研究提供了新的启示，成为数字空间表征研究中值得推崇的新取向。

关键词: 数字空间表征, 数形联觉, 心理数字线, 行为数据, 神经机制