Abstract: Investigated the development of elementary schoolersin one-dimensional spatial transitive inference and analyze the strategies children used during reasoning. At the same time, the mental model theory was examined. The participants were 72 children randomly selected from one middle-level primary school including three groups aged 7, 9 and 11 with half boys and half girls in each group. The experimental tasks included 4 types: single model with three premises, single model with four premises, two models with three premises, two models with four premises. The tests were carried out individually. Children reasoned in the condition of premises existing. The results showed that: (1) Children's ability of the one-dimensional spatial transitive reasoning increased significantly. The 7-year-olds developed this kind of reasoning ability, and the 9- and 11-year-olds had preliminarily possessed the ability; (2) The number of Children using the model constructing strategy to resolve problems became more and more with age. Nearly all 11-year-olds were able to use it. Even if children had used the model constructing strategy, the difference among task difficulty caused by the number of models isnot reflected by their reasoning performance.

Key words: primary school children, one-dimensional space, transitive inference