Preschool children’s intuitions of parallelism

Existing evidence has revealed that geometrical intuitions develop spontaneously without formal education. However, empirical research exploring the development of specific intuitive geometric concepts, such as parallelism, is still lacking. To explore preschoolers’ intuition of parallelism, one of the most fundamental concepts in geometry, a series of deviant-detection items were presented to 96 3- to 5-year-old children. Children showed the ability to discriminate between parallel and intersecting lines at least from the age of 4. We grouped children as discriminators and non-discriminators based on their performance in discriminating parallel and intersecting lines without a cross point. For the children who succeeded in this discrimination, they could distinguish parallel lines from intersecting lines both with and without a visible cross point, although they were easily interfered with the visible cross point. Children also showed some naïve understanding of parallel curves and could extract common features from parallel lines and parallel curves, suggesting that the extension of their intuitions of parallelism might be more general than the definition in Euclidean geometry.